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Baicalin, baicalein and wogonin inhibits high glucose-induced vascular inflammation in vitro and in vivo

Baicalin, baicalein and wogonin inhibits high glucose-induced vascular inflammation in vitro and... BMB Rep. 2015; 48(9): 519-524 BMB www.bmbreports.org Reports Baicalin, baicalein and wogonin inhibits high glucose-induced vascular inflammation in vitro and in vivo 1 2, Sae-Kwang Ku & Jong-Sup Bae 1 2 Department of Anatomy and Histology, College of Korean Medicine, Daegu Haany University, Gyeongsan 38610, College of Pharmacy, CMRI, Research Institute of Pharmaceutical Sciences, Kyungpook National University, Daegu 41566, Korea Vascular inflammatory process has been suggested to play a in 2000, after communicable diseases, cardiovascular disease, key role in initiation and progression of atherosclerosis, a ma- cancer, and injuries (4). In 2011, there were 366 million peo- jor complication of diabetes mellitus. Thus, in this study, we ple with DM in the world, and this number is expected to rise attempted to determine whether three structurally related poly- to 552 million by 2030; approximately 80% of these people phenols found in the Chinese herb Huang Qui, namely baica- reside in developing countries (1). Extensive investigations into lin, baicalein, and wogonin, can suppress vascular inflam- the pathogenesis of NIDDM have identified two endocrine de- matory processes induced by high glucose (HG) in human um- fects functionally: insulin deficiency and insulin resistance (1, 2). bilical vein endothelial cells (HUVECs) and mice. Data In modern medicine, an effective cure for DM is unavailable showed that HG induced markedly increased vascular perme- (5). Thus, the research for more effective agents than others ability, monocyte adhesion, expressions of cell adhesion mole- has continued. Many indigenous medicinal plants are useful in cules (CAMs), formation of reactive oxygen species (ROS) and controlling DM successfully; some effective compounds were activation of nuclear factor (NF)-B. Remarkably, all of the evaluated and found (6). The World Health Organization has above mentioned vascular inflammatory effects of HG were at- recommended the analysis of the potential of plants as effec- tenuated by pretreatment with baicalin, baicalein, and wogonin. tive therapeutic agents (7). Vascular inflammatory responses induced by HG are critical Scutellaria baicalensis Georgi (Huang-qin) is a medicinal events underlying development of various diabetic complica- herb used to treat various types of inflammatory diseases, hep- tions, therefore, our results suggest that baicalin, baicalein, and atitis, tumors, and diarrhea in East Asian countries such as wogonin may have significant therapeutic benefits against dia- China, Korea, Taiwan, and Japan (8). This plant contains many betic complications and atherosclerosis. [BMB Reports 2015; bioactive compounds including phenethyl alcohols, sterols, es- 48(9): 519-524] sential oils, and amino acids. Baicalin, baicalein, or wogonin is a single flavonoid isolated from Scutellaria baicalensis Georgi (9). The inhibitory activities of these flavonoids on vascular in- flammation have been attributed to suppress LPS-induced INTRODUCTION pro-inflammatory responses, for example, the productions of Diabetes mellitus (DM) is one of the metabolic disorders asso- nitric oxide and tumor necrosis factor-, and nitric oxide syn- ciated with various diseases, including arteriosclerosis, neph- thase gene expressions (10, 11). However, the effects of baica- ritis, and hypertension (1, 2). The most common type of DM is lin, baicalein, or wogonin on high-glucose (HG)-induced in- Non-insulin dependent diabetes mellitus (NIDDM) (1, 2); it is flammatory responses have not been reported. Therefore, in widespread, a growing threat to global public health, and has the current study, we attempted to determine whether baicalin the biggest impact on adults of working age in developing these compounds can suppress the vascular inflammatory re- countries (3). Often DM is not recorded as the cause of death, sponses induced by HG in human endothelial cells and in but globally it was considered the fifth leading cause of death mice. RESULTS AND DISCUSSION *Corresponding author. Tel: +82-53-950-8570; Fax: +82-53-950- 8557; E-mail: baejs@knu.ac.kr Baicalin, baicalein, and wogonin are three structurally similar http://dx.doi.org/10.5483/BMBRep.2015.48.9.017 polyphenols, which are active compounds found in the Chinese herb Huang-qin. In this study, the effects of these pol- Received 28 January 2015, Revised 17 February 2015, yphenols on HG-induced vascular inflammation were de- Accepted 2 March 2015 termined in vitro and in vivo. Keywords: Baicalein, Baicalin, Diabetes mellitus; Wogonin, High glucose ISSN: 1976-670X (electronic edition) Copyright ⓒ 2015 by the The Korean Society for Biochemistry and Molecular Biology This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/li- censes/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Effect of baicalin on diabetes Sae-Kwang Ku and Jong-Sup Bae 10 mM. Concentrations above 50 mM did not increase the Effects of polyphenols on HG-induced disruption of the HG-induced permeability further (data not shown). L-glucose endothelial barrier function of Human Umbilical Vein and D-Mannose (25 mM), which were used as an osmotic con- Endothelial Cells (HUVECs) and in mice trol, had no significant effect on endothelial cell permeability Previous evidence has suggested that endothelial dysfunction (Fig. 1A). and damage are precursors to vascular complications in DM Next, we attempted to determine whether baicalin, baicalein, (12). Hyperglycemia is the main precursor to all types of dia- and/or wogonin could alter HG-induced hyperpermeability. betic microvascular disease and may be involved in the patho- Treatment with 10 M of each compound alone did not result genesis of macrovascular complications as well (12-14). In ad- in alteration of barrier integrity (Fig. 1C). As shown in Fig. 1C, dition, endothelial cell permeability is impaired, and may be treatment with baicalin, baicalein, or wogonin resulted in a increased, by the high concentrations of extracellular glucose dose-dependent decrease in HG-mediated membrane dis- in diabetes mellitus (15). Leakage of serum proteins, partic- ruption; the minimum effect of baicalin, baicalein, or wogonin ularly albumin, through the endothelium is observed in the ret- was observed at 5 M. To confirm this vascular barrier pro- inal vessels of early-stage diabetes mellitus (15, 16). Increased tective effect in vivo, HG-mediated vascular permeability in endothelial cell permeability in the larger vessels leads to the mice was assessed. As shown in Fig. 1D, treatment with baica- development of interstitial edema and may result in the en- lin, baicalein, or wogonin resulted in significant inhibition of hancement of cell proliferation and matrix production (14). peritoneal leakage induced by HG. Because the average Therefore, we first investigated the effects of glucose on the al- weight of a mouse is 20 g and the average blood volume is 2 bumin permeability of endothelial cells, as shown in Fig. 1A. mL, the injected baicalin (1.1, 2.7, or 5.4 g/mouse), baicalein Treatment with HG (25 and 50 mM) led to a rapid increase in (1.8, 4.5, or 8.9 g/mouse), or wogonin (1.1, 2.8, or 5.7 endothelial cell permeability (Fig. 1A). This effect began 12 h g/mouse) produced concentration maximums of 2, 5, or 10 after incubation and reached its maximum at 24 h (Fig. 1B). A M in the peripheral blood. To test the effects of the cellular significant increase was observed at a glucose concentration of Fig. 1. Effects of polyphenols on HG- mediated permeability in vitro and in vivo. (A) HUVECs were treated with D-glucose (0-50 mM), L-glucose (25 mM), and D-mannitol (25 mM) for 24 h and permeability was monitored by measuring the flux of Evans-blue-dye- bound albumin across HUVECs. (B) HUVECs were treated with D-glucose (25 mM) for indicated time periods and permeability was monitored. (C) The effects of pretreatment with differ- ent concentrations of baicalin (white bar), baicalein (gray bar) and wogonin (black bar) for 6 h on barrier disrup- tions caused by 25 mM HG for 24 h. (D) The effects of baicalin (white bar), baicalein (gray bar) and wogonin (black bar) injected intravenously on HG-in- duced (9 mg/mouse, i.v.) vascular per- meability in mice were determined by measuring the levels of Evans blue dye in peritoneal washings (expressed g/mouse, n = 5). (E) The effects of baicalin (white bar), baicalein (gray bar) and wogonin (black bar) on cellular viability were measured using MTT assays. Results are expressed as the mean ± SEM of at least three in- dependent experiments. *P < 0.05 versus 0 (A, B), HG alone (C, D). 520 BMB Reports http://bmbreports.org Effect of baicalin on diabetes Sae-Kwang Ku and Jong-Sup Bae viability of baicalin, baicalein, or wogonin, MTT assays were been observed in the endothelial cells of human athero- performed on HUVECs treated with each compound for 24 h. sclerotic lesions (22). The expression of CAMs on endothelial At the concentrations used (up to 50 M), baicalin, baicalein, cells by HG has been widely studied. It was reported that HG or wogonin did not affect the viability of HUVECs (Fig. 1E). increased the expression of ICAM-1 in human aortic endothe- These findings indicated the inhibitory effects of baicalin, bai- lial cells (23); this study is consistent with findings indicating calein, and wogonin on HG-mediated endothelial dysfunc- that HG is a mediator of leukocyte adhesion toward endothe- tions and barrier disruptive responses in mice. Therefore, pre- lial cells, counting on the enhanced expressions of VCAM-1, vention of HG-induced barrier disruption by each compound ICAM-1, and E-selectin (20). Furthermore, the adhesion of leu- suggested the potential of baicalin, baicalein, or wogonin to kocytes toward the endothelial cells is followed by their migra- treat vascular inflammatory diseases. tion and differentiation into macrophages, which is controlled by an interaction between the monocytes and CAMs (24). Effects of polyphenols on HG-mediated expression of cell Therefore, we evaluated the effects of HG on the expression of adhesion molecules (CAMs) and THP-1 adhesion CAMs and adhesion of monocytes to HUVECs in response to Two important phenomena that occur early in the pathology of HG. The HG concentration-based responses in the expression atherosclerosis are the adhesion of leukocytes to the endothe- of CAMs, such as VCAM-1, ICAM-1, and E-selectin, were de- lial layers, followed by the migration into the inflammatory termined by enzyme-linked immunosorbent assay. Exposure of sites, and enhanced vascular permeability (15, 17). Enhanced the primary cultured HUVECs to HG resulted in significantly interactions between leukocyte and endothelial cells have increased expression of CAMs after incubation with 25 mM been demonstrated in in vivo and in vitro diabetes models D-glucose; the maximum inhibitory effect of baicalin, baica- (17, 18). NF-B activation is the major controller in enhanced lein, or wogonin (Fig. 2A) was observed at 10 M. expressions of CAMs and migration of leukocytes through en- And, to determine the effect of baicalin, baicalein, or wogo- dothelium by HG (19, 20). In addition, it is well known that nin on the interaction between endothelial cell and leukocyte, the upregulation of CAMs is involved in the pathology of athe- we tested the adhesion of THP-1 cells to HG-activated HUVECs rosclerosis (21). The interactions between endothelium and and the migration of leukocytes in vivo. Adhesion of THP-1 leukocytes such as the adhesion and migrations of leukocytes, cells to HUVECs was increased significantly with HG treatments. which is a precursor to atheroma (21). Particularly, upreluation Pretreatment with baicalin, baicalein, or wogonin (10 M) re- of CAMs such as vascular cell adhesion molecule-1 (VCAM-1), sulted in a decreased number of THP-1 cells adhering to intracellular adhesion molecule-1 (ICAM-1), and E-selectin has HG-induced HUVECs (Fig. 2B and 2C). These results were cor- Fig. 2. Effects of polyphenols on HG- mediated pro-inflammatory responses. HG-induced (25 mM, for 24 h) ex- pression of cell adhesion molecules on HUVECs was determined after treat- ment of cells with the indicated con- centrations of baicalin, baicalein and wogonin for 6 h. VCAM-1 (white bar), ICAM-1 (gray bar), and E-Selectin (black bar) were detected by ELISA. (B, C) HG-induced (25 mM, for 24 h)-me- diated adherence of monocytes to HUVEC monolayers was assessed after pretreatment of cells with baicalin, baicalein and wogonin for 6 h. The amounts of adherent THP-1 cells were monitored by (B) cell-cell adhesion as- say and (C) fluorescence microscopy. (D) The same as Fig. 1D except that the leukocyte migration into the peri- toneal cavities of mice was analyzed. Data are expressed as the mean ± SEM of three independent experiments. *P < 0.05 and *P < 0.05 vs. HG alone. http://bmbreports.org BMB Reports 521 Effect of baicalin on diabetes Sae-Kwang Ku and Jong-Sup Bae Fig. 3. Effects of polyphenols on HG- induced expression of MCP-1 and IL-8 mRNA and ROS formation. (A, B) Cells were pretreated with baicalin, baicalein and wogonin for 6 h and then incubated with HG (25 mM) for 48 h. mRNA was extracted, and real time qRT-PCR analysis was performed using specific primer for MCP-1 (A), IL-8 (B), and GAPDH, as described in the Materials and methods section. (C) Cells were pretreated with baicalin, baicalein and wogonin for 6 h and then stimulated with HG for 1 h; H O assay was then performed as 2 2 described in the Materials and meth- ods section. Data are expressed as the mean ± SEM of three independent experiments. *P < 0.05 vs. HG alone. roborated in vivo by the inhibition of HG-induced migration of cellular H2O2 concentrations were measured. H2O2 levels leukocytes in the peritoneal space (Fig. 2D). Thus, baicalin, were statistically increased after incubation for 10 min with 25 baicalein, or wogonin could be a therapeutic drug candidate mM glucose; the maximum concentrations were observed af- for diabetic vascular inflammation by targeting CAMs ex- ter 1 h incubation (data not shown). Therefore, 1 h incubation pression in the prevention of atherosclerotic lesions. condition was chosen to analyze cellular ROS in further IL-8 and MCP-1 are chemokines strongly implicated in the experiments. As shown in Fig. 3C, pretreatment with 10 M atherogenesis processes (25). IL-8 funtions as a chemotactic for baicalin, baicalein, or wogonin significantly inhibited HG-in- neutrophils and MCP-1 is a important mediator of monocyte duced increase in H2O2 levels. In addition, baicalin, baicalein, trafficking (25). Therefore, we tested the hypothesis that baica- or wogonin alone did not mediate oxidative stress (data not lin, baicalein, and/or wogonin would inhibit HG-induced shown), which suggested the importance of HG-mediated oxi- MCP-1 and IL-8 mRNA levels using real time reverse tran- dative stress on HUVECs in determining the characteristics of scription polymerase chain reaction. As shown in Fig. 3A and diabetic complications and vascular inflammation. 3B, HG induced an increase in the expression levels of MCP-1 (up to 5.2-fold) and IL-8 (up to 4.7-fold) mRNA; pretreatment Effect of polyphenols on HG-induced activation of NF-B with baicalin, baicalein, or wogonin resulted in decreased ex- Activation NF-B affects the uprelations of CAMs and induces pression levels of HG-induced MCP-1 and IL-8 mRNA. These interconnected activations of other pro-inflammatory chemo- results suggested that baicalin, baicalein, or wogonin might be attractants and cytokines, which could provide the biological useful in preventing the diabetic inflammatory process. relationship between endothelial cell dysfunction and cell re- dox states (29). In addition, ROS activates various transcription Effect of polyphenols on HG-induced oxidative stress factors in cultured endothelial cells, including NF-B (30). The synthesis of reactive oxygen species (ROS) is physiologi- First, we measured HG-induced translocation of NF-B from cally related with inflammatory responses (26). Previous ob- the cytosol into the nucleus. NF-B p65 proteins are the active servations have indicated that HG raises the oxidant stress and subunits of the NF-B complex. Increased levels of p65 pro- the synthesis of free radicals in various types of cells; ROS are teins in the nuclear extracts of HUVECs treated with HG were the key mediator of various oxidative events such as extra- shown using western blotting analysis, and the cytosolic ex- cellular matrix deposition and cell proliferation (27, 28). There- tracts exhibited an appreciable loss of p65 protein content (Fig. fore, to determine the cyto-protective effect of baicalin, baica- 4A). And, treatment with baicalin, baicalein, or wogonin re- lein, or wogonin on HG-induced oxidative stress, HG-induced sulted in the inhibition of HG-induced increases in p65 NF-B 522 BMB Reports http://bmbreports.org Effect of baicalin on diabetes Sae-Kwang Ku and Jong-Sup Bae Fig. 4. Effects of polyphenols on HG- induced activation of NF-B. Cells were pretreated with baicalin, baica- lein and wogonin for 6 h and then stimulated with HG for 1 h. (A) The expression levels of NF-B in nuclear extract or cytoplasmic extract were tested by western blotting. -actin or lamin A/C was used as a loading control for cytoplasmic or nuclear ex- tracts, respectively. (B) NF-B 65 was visualized using rabbit anti-p65 mono- clonal antibody (1:100), which only re- cognized NF-B p65. Goat anti-rabbit antibody (1:100) conjugated to FITC was performed. The subcellular local- ization of NF-B p65 was examined by immunofluorescence staining and vi- sualized under an immunofluorescence microscope. The images are representa- tive of results from three independent experiments. expression levels (Fig. 4A). To confirm the western blotting re- MATERIALS AND METHODS sults, immunocytochemistry was applied using p65 NF-B and FITC-conjugated antibodies. The results showed that HG in- Please see the supplementary materials for materials and creased the p65 NF-B expression in the nucleus, whereas methods. normal conditions did not. And, treatment with 10 M baica- lin, baicalein, or wogonin resulted in a decrease in the HG-in- ACKNOWLEDGEMENTS duced expression of p65 NF-B in the nucleus, which were consistent with those of western blotting (Fig. 4A); they dem- This study was supported by the National Research Foundation onstrated that the HG-mediated NF-B activation was in- of Korea (NRF) funded by the Korea government [MSIP] (Grant hibited by baicalin, baicalein, and wogonin, indicating that Nos. 2012R1A5A2A42671316 and 2014R1A2A1A11049526). baicalin, baicalein, or wogonin have inhibitory effects on the NF-B pathways specific to HG-induced adhesion molecules REFERENCES on HUVECs. In summary, our results demonstrated that treatment with 1. Whiting DR, Guariguata L, Weil C and Shaw J (2011) IDF baicalin, baicalein, or wogonin resulted in a blockage of HG- diabetes atlas: global estimates of the prevalence of dia- betes for 2011 and 2030. 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Baicalin, baicalein and wogonin inhibits high glucose-induced vascular inflammation in vitro and in vivo

BMB Reports , Volume 48 (9) – Sep 1, 2015

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BMB Rep. 2015; 48(9): 519-524 BMB www.bmbreports.org Reports Baicalin, baicalein and wogonin inhibits high glucose-induced vascular inflammation in vitro and in vivo 1 2, Sae-Kwang Ku & Jong-Sup Bae 1 2 Department of Anatomy and Histology, College of Korean Medicine, Daegu Haany University, Gyeongsan 38610, College of Pharmacy, CMRI, Research Institute of Pharmaceutical Sciences, Kyungpook National University, Daegu 41566, Korea Vascular inflammatory process has been suggested to play a in 2000, after communicable diseases, cardiovascular disease, key role in initiation and progression of atherosclerosis, a ma- cancer, and injuries (4). In 2011, there were 366 million peo- jor complication of diabetes mellitus. Thus, in this study, we ple with DM in the world, and this number is expected to rise attempted to determine whether three structurally related poly- to 552 million by 2030; approximately 80% of these people phenols found in the Chinese herb Huang Qui, namely baica- reside in developing countries (1). Extensive investigations into lin, baicalein, and wogonin, can suppress vascular inflam- the pathogenesis of NIDDM have identified two endocrine de- matory processes induced by high glucose (HG) in human um- fects functionally: insulin deficiency and insulin resistance (1, 2). bilical vein endothelial cells (HUVECs) and mice. Data In modern medicine, an effective cure for DM is unavailable showed that HG induced markedly increased vascular perme- (5). Thus, the research for more effective agents than others ability, monocyte adhesion, expressions of cell adhesion mole- has continued. Many indigenous medicinal plants are useful in cules (CAMs), formation of reactive oxygen species (ROS) and controlling DM successfully; some effective compounds were activation of nuclear factor (NF)-B. Remarkably, all of the evaluated and found (6). The World Health Organization has above mentioned vascular inflammatory effects of HG were at- recommended the analysis of the potential of plants as effec- tenuated by pretreatment with baicalin, baicalein, and wogonin. tive therapeutic agents (7). Vascular inflammatory responses induced by HG are critical Scutellaria baicalensis Georgi (Huang-qin) is a medicinal events underlying development of various diabetic complica- herb used to treat various types of inflammatory diseases, hep- tions, therefore, our results suggest that baicalin, baicalein, and atitis, tumors, and diarrhea in East Asian countries such as wogonin may have significant therapeutic benefits against dia- China, Korea, Taiwan, and Japan (8). This plant contains many betic complications and atherosclerosis. [BMB Reports 2015; bioactive compounds including phenethyl alcohols, sterols, es- 48(9): 519-524] sential oils, and amino acids. Baicalin, baicalein, or wogonin is a single flavonoid isolated from Scutellaria baicalensis Georgi (9). The inhibitory activities of these flavonoids on vascular in- flammation have been attributed to suppress LPS-induced INTRODUCTION pro-inflammatory responses, for example, the productions of Diabetes mellitus (DM) is one of the metabolic disorders asso- nitric oxide and tumor necrosis factor-, and nitric oxide syn- ciated with various diseases, including arteriosclerosis, neph- thase gene expressions (10, 11). However, the effects of baica- ritis, and hypertension (1, 2). The most common type of DM is lin, baicalein, or wogonin on high-glucose (HG)-induced in- Non-insulin dependent diabetes mellitus (NIDDM) (1, 2); it is flammatory responses have not been reported. Therefore, in widespread, a growing threat to global public health, and has the current study, we attempted to determine whether baicalin the biggest impact on adults of working age in developing these compounds can suppress the vascular inflammatory re- countries (3). Often DM is not recorded as the cause of death, sponses induced by HG in human endothelial cells and in but globally it was considered the fifth leading cause of death mice. RESULTS AND DISCUSSION *Corresponding author. Tel: +82-53-950-8570; Fax: +82-53-950- 8557; E-mail: baejs@knu.ac.kr Baicalin, baicalein, and wogonin are three structurally similar http://dx.doi.org/10.5483/BMBRep.2015.48.9.017 polyphenols, which are active compounds found in the Chinese herb Huang-qin. In this study, the effects of these pol- Received 28 January 2015, Revised 17 February 2015, yphenols on HG-induced vascular inflammation were de- Accepted 2 March 2015 termined in vitro and in vivo. Keywords: Baicalein, Baicalin, Diabetes mellitus; Wogonin, High glucose ISSN: 1976-670X (electronic edition) Copyright ⓒ 2015 by the The Korean Society for Biochemistry and Molecular Biology This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/li- censes/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Effect of baicalin on diabetes Sae-Kwang Ku and Jong-Sup Bae 10 mM. Concentrations above 50 mM did not increase the Effects of polyphenols on HG-induced disruption of the HG-induced permeability further (data not shown). L-glucose endothelial barrier function of Human Umbilical Vein and D-Mannose (25 mM), which were used as an osmotic con- Endothelial Cells (HUVECs) and in mice trol, had no significant effect on endothelial cell permeability Previous evidence has suggested that endothelial dysfunction (Fig. 1A). and damage are precursors to vascular complications in DM Next, we attempted to determine whether baicalin, baicalein, (12). Hyperglycemia is the main precursor to all types of dia- and/or wogonin could alter HG-induced hyperpermeability. betic microvascular disease and may be involved in the patho- Treatment with 10 M of each compound alone did not result genesis of macrovascular complications as well (12-14). In ad- in alteration of barrier integrity (Fig. 1C). As shown in Fig. 1C, dition, endothelial cell permeability is impaired, and may be treatment with baicalin, baicalein, or wogonin resulted in a increased, by the high concentrations of extracellular glucose dose-dependent decrease in HG-mediated membrane dis- in diabetes mellitus (15). Leakage of serum proteins, partic- ruption; the minimum effect of baicalin, baicalein, or wogonin ularly albumin, through the endothelium is observed in the ret- was observed at 5 M. To confirm this vascular barrier pro- inal vessels of early-stage diabetes mellitus (15, 16). Increased tective effect in vivo, HG-mediated vascular permeability in endothelial cell permeability in the larger vessels leads to the mice was assessed. As shown in Fig. 1D, treatment with baica- development of interstitial edema and may result in the en- lin, baicalein, or wogonin resulted in significant inhibition of hancement of cell proliferation and matrix production (14). peritoneal leakage induced by HG. Because the average Therefore, we first investigated the effects of glucose on the al- weight of a mouse is 20 g and the average blood volume is 2 bumin permeability of endothelial cells, as shown in Fig. 1A. mL, the injected baicalin (1.1, 2.7, or 5.4 g/mouse), baicalein Treatment with HG (25 and 50 mM) led to a rapid increase in (1.8, 4.5, or 8.9 g/mouse), or wogonin (1.1, 2.8, or 5.7 endothelial cell permeability (Fig. 1A). This effect began 12 h g/mouse) produced concentration maximums of 2, 5, or 10 after incubation and reached its maximum at 24 h (Fig. 1B). A M in the peripheral blood. To test the effects of the cellular significant increase was observed at a glucose concentration of Fig. 1. Effects of polyphenols on HG- mediated permeability in vitro and in vivo. (A) HUVECs were treated with D-glucose (0-50 mM), L-glucose (25 mM), and D-mannitol (25 mM) for 24 h and permeability was monitored by measuring the flux of Evans-blue-dye- bound albumin across HUVECs. (B) HUVECs were treated with D-glucose (25 mM) for indicated time periods and permeability was monitored. (C) The effects of pretreatment with differ- ent concentrations of baicalin (white bar), baicalein (gray bar) and wogonin (black bar) for 6 h on barrier disrup- tions caused by 25 mM HG for 24 h. (D) The effects of baicalin (white bar), baicalein (gray bar) and wogonin (black bar) injected intravenously on HG-in- duced (9 mg/mouse, i.v.) vascular per- meability in mice were determined by measuring the levels of Evans blue dye in peritoneal washings (expressed g/mouse, n = 5). (E) The effects of baicalin (white bar), baicalein (gray bar) and wogonin (black bar) on cellular viability were measured using MTT assays. Results are expressed as the mean ± SEM of at least three in- dependent experiments. *P < 0.05 versus 0 (A, B), HG alone (C, D). 520 BMB Reports http://bmbreports.org Effect of baicalin on diabetes Sae-Kwang Ku and Jong-Sup Bae viability of baicalin, baicalein, or wogonin, MTT assays were been observed in the endothelial cells of human athero- performed on HUVECs treated with each compound for 24 h. sclerotic lesions (22). The expression of CAMs on endothelial At the concentrations used (up to 50 M), baicalin, baicalein, cells by HG has been widely studied. It was reported that HG or wogonin did not affect the viability of HUVECs (Fig. 1E). increased the expression of ICAM-1 in human aortic endothe- These findings indicated the inhibitory effects of baicalin, bai- lial cells (23); this study is consistent with findings indicating calein, and wogonin on HG-mediated endothelial dysfunc- that HG is a mediator of leukocyte adhesion toward endothe- tions and barrier disruptive responses in mice. Therefore, pre- lial cells, counting on the enhanced expressions of VCAM-1, vention of HG-induced barrier disruption by each compound ICAM-1, and E-selectin (20). Furthermore, the adhesion of leu- suggested the potential of baicalin, baicalein, or wogonin to kocytes toward the endothelial cells is followed by their migra- treat vascular inflammatory diseases. tion and differentiation into macrophages, which is controlled by an interaction between the monocytes and CAMs (24). Effects of polyphenols on HG-mediated expression of cell Therefore, we evaluated the effects of HG on the expression of adhesion molecules (CAMs) and THP-1 adhesion CAMs and adhesion of monocytes to HUVECs in response to Two important phenomena that occur early in the pathology of HG. The HG concentration-based responses in the expression atherosclerosis are the adhesion of leukocytes to the endothe- of CAMs, such as VCAM-1, ICAM-1, and E-selectin, were de- lial layers, followed by the migration into the inflammatory termined by enzyme-linked immunosorbent assay. Exposure of sites, and enhanced vascular permeability (15, 17). Enhanced the primary cultured HUVECs to HG resulted in significantly interactions between leukocyte and endothelial cells have increased expression of CAMs after incubation with 25 mM been demonstrated in in vivo and in vitro diabetes models D-glucose; the maximum inhibitory effect of baicalin, baica- (17, 18). NF-B activation is the major controller in enhanced lein, or wogonin (Fig. 2A) was observed at 10 M. expressions of CAMs and migration of leukocytes through en- And, to determine the effect of baicalin, baicalein, or wogo- dothelium by HG (19, 20). In addition, it is well known that nin on the interaction between endothelial cell and leukocyte, the upregulation of CAMs is involved in the pathology of athe- we tested the adhesion of THP-1 cells to HG-activated HUVECs rosclerosis (21). The interactions between endothelium and and the migration of leukocytes in vivo. Adhesion of THP-1 leukocytes such as the adhesion and migrations of leukocytes, cells to HUVECs was increased significantly with HG treatments. which is a precursor to atheroma (21). Particularly, upreluation Pretreatment with baicalin, baicalein, or wogonin (10 M) re- of CAMs such as vascular cell adhesion molecule-1 (VCAM-1), sulted in a decreased number of THP-1 cells adhering to intracellular adhesion molecule-1 (ICAM-1), and E-selectin has HG-induced HUVECs (Fig. 2B and 2C). These results were cor- Fig. 2. Effects of polyphenols on HG- mediated pro-inflammatory responses. HG-induced (25 mM, for 24 h) ex- pression of cell adhesion molecules on HUVECs was determined after treat- ment of cells with the indicated con- centrations of baicalin, baicalein and wogonin for 6 h. VCAM-1 (white bar), ICAM-1 (gray bar), and E-Selectin (black bar) were detected by ELISA. (B, C) HG-induced (25 mM, for 24 h)-me- diated adherence of monocytes to HUVEC monolayers was assessed after pretreatment of cells with baicalin, baicalein and wogonin for 6 h. The amounts of adherent THP-1 cells were monitored by (B) cell-cell adhesion as- say and (C) fluorescence microscopy. (D) The same as Fig. 1D except that the leukocyte migration into the peri- toneal cavities of mice was analyzed. Data are expressed as the mean ± SEM of three independent experiments. *P < 0.05 and *P < 0.05 vs. HG alone. http://bmbreports.org BMB Reports 521 Effect of baicalin on diabetes Sae-Kwang Ku and Jong-Sup Bae Fig. 3. Effects of polyphenols on HG- induced expression of MCP-1 and IL-8 mRNA and ROS formation. (A, B) Cells were pretreated with baicalin, baicalein and wogonin for 6 h and then incubated with HG (25 mM) for 48 h. mRNA was extracted, and real time qRT-PCR analysis was performed using specific primer for MCP-1 (A), IL-8 (B), and GAPDH, as described in the Materials and methods section. (C) Cells were pretreated with baicalin, baicalein and wogonin for 6 h and then stimulated with HG for 1 h; H O assay was then performed as 2 2 described in the Materials and meth- ods section. Data are expressed as the mean ± SEM of three independent experiments. *P < 0.05 vs. HG alone. roborated in vivo by the inhibition of HG-induced migration of cellular H2O2 concentrations were measured. H2O2 levels leukocytes in the peritoneal space (Fig. 2D). Thus, baicalin, were statistically increased after incubation for 10 min with 25 baicalein, or wogonin could be a therapeutic drug candidate mM glucose; the maximum concentrations were observed af- for diabetic vascular inflammation by targeting CAMs ex- ter 1 h incubation (data not shown). Therefore, 1 h incubation pression in the prevention of atherosclerotic lesions. condition was chosen to analyze cellular ROS in further IL-8 and MCP-1 are chemokines strongly implicated in the experiments. As shown in Fig. 3C, pretreatment with 10 M atherogenesis processes (25). IL-8 funtions as a chemotactic for baicalin, baicalein, or wogonin significantly inhibited HG-in- neutrophils and MCP-1 is a important mediator of monocyte duced increase in H2O2 levels. In addition, baicalin, baicalein, trafficking (25). Therefore, we tested the hypothesis that baica- or wogonin alone did not mediate oxidative stress (data not lin, baicalein, and/or wogonin would inhibit HG-induced shown), which suggested the importance of HG-mediated oxi- MCP-1 and IL-8 mRNA levels using real time reverse tran- dative stress on HUVECs in determining the characteristics of scription polymerase chain reaction. As shown in Fig. 3A and diabetic complications and vascular inflammation. 3B, HG induced an increase in the expression levels of MCP-1 (up to 5.2-fold) and IL-8 (up to 4.7-fold) mRNA; pretreatment Effect of polyphenols on HG-induced activation of NF-B with baicalin, baicalein, or wogonin resulted in decreased ex- Activation NF-B affects the uprelations of CAMs and induces pression levels of HG-induced MCP-1 and IL-8 mRNA. These interconnected activations of other pro-inflammatory chemo- results suggested that baicalin, baicalein, or wogonin might be attractants and cytokines, which could provide the biological useful in preventing the diabetic inflammatory process. relationship between endothelial cell dysfunction and cell re- dox states (29). In addition, ROS activates various transcription Effect of polyphenols on HG-induced oxidative stress factors in cultured endothelial cells, including NF-B (30). The synthesis of reactive oxygen species (ROS) is physiologi- First, we measured HG-induced translocation of NF-B from cally related with inflammatory responses (26). Previous ob- the cytosol into the nucleus. NF-B p65 proteins are the active servations have indicated that HG raises the oxidant stress and subunits of the NF-B complex. Increased levels of p65 pro- the synthesis of free radicals in various types of cells; ROS are teins in the nuclear extracts of HUVECs treated with HG were the key mediator of various oxidative events such as extra- shown using western blotting analysis, and the cytosolic ex- cellular matrix deposition and cell proliferation (27, 28). There- tracts exhibited an appreciable loss of p65 protein content (Fig. fore, to determine the cyto-protective effect of baicalin, baica- 4A). And, treatment with baicalin, baicalein, or wogonin re- lein, or wogonin on HG-induced oxidative stress, HG-induced sulted in the inhibition of HG-induced increases in p65 NF-B 522 BMB Reports http://bmbreports.org Effect of baicalin on diabetes Sae-Kwang Ku and Jong-Sup Bae Fig. 4. Effects of polyphenols on HG- induced activation of NF-B. Cells were pretreated with baicalin, baica- lein and wogonin for 6 h and then stimulated with HG for 1 h. (A) The expression levels of NF-B in nuclear extract or cytoplasmic extract were tested by western blotting. -actin or lamin A/C was used as a loading control for cytoplasmic or nuclear ex- tracts, respectively. (B) NF-B 65 was visualized using rabbit anti-p65 mono- clonal antibody (1:100), which only re- cognized NF-B p65. Goat anti-rabbit antibody (1:100) conjugated to FITC was performed. The subcellular local- ization of NF-B p65 was examined by immunofluorescence staining and vi- sualized under an immunofluorescence microscope. The images are representa- tive of results from three independent experiments. expression levels (Fig. 4A). To confirm the western blotting re- MATERIALS AND METHODS sults, immunocytochemistry was applied using p65 NF-B and FITC-conjugated antibodies. The results showed that HG in- Please see the supplementary materials for materials and creased the p65 NF-B expression in the nucleus, whereas methods. normal conditions did not. And, treatment with 10 M baica- lin, baicalein, or wogonin resulted in a decrease in the HG-in- ACKNOWLEDGEMENTS duced expression of p65 NF-B in the nucleus, which were consistent with those of western blotting (Fig. 4A); they dem- This study was supported by the National Research Foundation onstrated that the HG-mediated NF-B activation was in- of Korea (NRF) funded by the Korea government [MSIP] (Grant hibited by baicalin, baicalein, and wogonin, indicating that Nos. 2012R1A5A2A42671316 and 2014R1A2A1A11049526). baicalin, baicalein, or wogonin have inhibitory effects on the NF-B pathways specific to HG-induced adhesion molecules REFERENCES on HUVECs. In summary, our results demonstrated that treatment with 1. Whiting DR, Guariguata L, Weil C and Shaw J (2011) IDF baicalin, baicalein, or wogonin resulted in a blockage of HG- diabetes atlas: global estimates of the prevalence of dia- betes for 2011 and 2030. 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Published: Sep 1, 2015

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