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Protective effects of vascular endothelial growth factor in cultured brain endothelial cells against hypoglycemia.

Zhao F, Deng J, Yu X, Li D, Shi H, Zhao Y - Metab Brain Dis (2015)

Bottom Line: Whether VEGF has a protective effect against hypoglycemia-induced damage in brain endothelial cells is still unknown.Besides, transendothelial permeability significantly increased under hypoglycemic conditions compared to that under control conditions.Moreover, the hypoglycemic medium in presence of VEGF decreased endothelial permeability via the inhibition of claudin-5 degradation and improved hypoglycemia-induced cell toxicity.

View Article: PubMed Central - PubMed

Affiliation: Neurologic Department, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, No.600, Yishan Road, Xuhui District, Shanghai, 200233, China.

ABSTRACT
Hypoglycemia is a common and serious problem among patients with type 1 diabetes receiving treatment with insulin. Clinical studies have demonstrated that hypoglycemic edema is involved in the initiation of hypoglycemic brain damage. However, the mechanisms of this edema are poorly understood. Vascular endothelial growth factor (VEGF), a potent regulator of blood vessel function, has been observed an important candidate hormone induced by hypoglycemia to protect neurons by restoring plasma glucose. Whether VEGF has a protective effect against hypoglycemia-induced damage in brain endothelial cells is still unknown. To investigate the effects of hypoglycemia on cerebral microvascular endothelial cells and assess the protective effect of exogenous VEGF on endothelial cells during hypoglycemia, confluent monolayers of the brain endothelial cell line bEnd.3 were treated with normal (5.5 mM glucose), hypoglycemic (0, 0.5, 1 mM glucose) medium or hypoglycemic medium in the presence of VEGF. The results clearly showed that hypoglycemia significantly downregulated the expression of claudin-5 in bEnd.3 cells, without affecting ZO-1 and occludin expression and distribution. Besides, transendothelial permeability significantly increased under hypoglycemic conditions compared to that under control conditions. Moreover, the hypoglycemic medium in presence of VEGF decreased endothelial permeability via the inhibition of claudin-5 degradation and improved hypoglycemia-induced cell toxicity. Furthermore, Glucose transporter-1 (Glut-1) and apoptosis regulator Bcl-2 expression were significantly upregulated. Taken together, hypoglycemia can significantly increase paraendocellular permeability by downregulating claudin-5 expression. We further showed that VEGF protected brain endothelial cells against hypoglycemia by enhancing glucose passage, reducing endothelial cell death, and ameliorating paraendocellular permeability.

No MeSH data available.


Related in: MedlinePlus

Effects of hypoglycemia on TJ proteins in bEnd.3 cells. Confluent bEnd.3 monolayers were exposed to 0 mM (a), 0.5 mM (b), 1 mM (c), or 5.5 mM (d, control) glucose for 1, 3, 6, 12, or 24 h. Representative blots for ZO-1, occludin, claudin-5, and β-actin are shown. Summary plots of ZO-1 (e), occludin (f), and claudin-5 (g) expression, including densitometric reading of the corresponding protein blots, are shown. Data are expressed as the mean ± SEM. N = 3. *P < 0.05, **P < 0.01
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Fig2: Effects of hypoglycemia on TJ proteins in bEnd.3 cells. Confluent bEnd.3 monolayers were exposed to 0 mM (a), 0.5 mM (b), 1 mM (c), or 5.5 mM (d, control) glucose for 1, 3, 6, 12, or 24 h. Representative blots for ZO-1, occludin, claudin-5, and β-actin are shown. Summary plots of ZO-1 (e), occludin (f), and claudin-5 (g) expression, including densitometric reading of the corresponding protein blots, are shown. Data are expressed as the mean ± SEM. N = 3. *P < 0.05, **P < 0.01

Mentions: Tight junctions integrity is a hallmark of brain edema progression in pathological conditions such as stroke (Jiao et al. 2011). It has been shown that TJ proteins, including occludin, ZO-1, and claudin-5, have an important role in the integrity of the BBB (Sandoval and Witt 2008). To investigate whether these proteins have a major role in hypoglycemia, western blot and immunofluorescence analyses were performed to detect the protein expression levels. As shown in Fig. 2, western blot analysis revealed that hypoglycemia induced a time- and glucose dose-dependent decrease in claudin-5 protein levels. However, hypoglycemia did not significantly change ZO-1 and occludin expression compared to the control (5.5 mM glucose). Furthermore, as shown in Fig. 3, immunofluorescence imaging confirmed that hypoglycemia did not alter the localization of claudin-5, ZO-1, and occludin after 6, 12, or 24 h treatment, although occludin is displayed diffuse cytoplasmic localization in bEnd.3 (data not shown). These results were consistent with the observed hypoglycemia-induced permeability increase in the endothelial monolayer. These data suggested that disruption of claudin-5 may increase BBB permeability.Fig. 2


Protective effects of vascular endothelial growth factor in cultured brain endothelial cells against hypoglycemia.

Zhao F, Deng J, Yu X, Li D, Shi H, Zhao Y - Metab Brain Dis (2015)

Effects of hypoglycemia on TJ proteins in bEnd.3 cells. Confluent bEnd.3 monolayers were exposed to 0 mM (a), 0.5 mM (b), 1 mM (c), or 5.5 mM (d, control) glucose for 1, 3, 6, 12, or 24 h. Representative blots for ZO-1, occludin, claudin-5, and β-actin are shown. Summary plots of ZO-1 (e), occludin (f), and claudin-5 (g) expression, including densitometric reading of the corresponding protein blots, are shown. Data are expressed as the mean ± SEM. N = 3. *P < 0.05, **P < 0.01
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4491374&req=5

Fig2: Effects of hypoglycemia on TJ proteins in bEnd.3 cells. Confluent bEnd.3 monolayers were exposed to 0 mM (a), 0.5 mM (b), 1 mM (c), or 5.5 mM (d, control) glucose for 1, 3, 6, 12, or 24 h. Representative blots for ZO-1, occludin, claudin-5, and β-actin are shown. Summary plots of ZO-1 (e), occludin (f), and claudin-5 (g) expression, including densitometric reading of the corresponding protein blots, are shown. Data are expressed as the mean ± SEM. N = 3. *P < 0.05, **P < 0.01
Mentions: Tight junctions integrity is a hallmark of brain edema progression in pathological conditions such as stroke (Jiao et al. 2011). It has been shown that TJ proteins, including occludin, ZO-1, and claudin-5, have an important role in the integrity of the BBB (Sandoval and Witt 2008). To investigate whether these proteins have a major role in hypoglycemia, western blot and immunofluorescence analyses were performed to detect the protein expression levels. As shown in Fig. 2, western blot analysis revealed that hypoglycemia induced a time- and glucose dose-dependent decrease in claudin-5 protein levels. However, hypoglycemia did not significantly change ZO-1 and occludin expression compared to the control (5.5 mM glucose). Furthermore, as shown in Fig. 3, immunofluorescence imaging confirmed that hypoglycemia did not alter the localization of claudin-5, ZO-1, and occludin after 6, 12, or 24 h treatment, although occludin is displayed diffuse cytoplasmic localization in bEnd.3 (data not shown). These results were consistent with the observed hypoglycemia-induced permeability increase in the endothelial monolayer. These data suggested that disruption of claudin-5 may increase BBB permeability.Fig. 2

Bottom Line: Whether VEGF has a protective effect against hypoglycemia-induced damage in brain endothelial cells is still unknown.Besides, transendothelial permeability significantly increased under hypoglycemic conditions compared to that under control conditions.Moreover, the hypoglycemic medium in presence of VEGF decreased endothelial permeability via the inhibition of claudin-5 degradation and improved hypoglycemia-induced cell toxicity.

View Article: PubMed Central - PubMed

Affiliation: Neurologic Department, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, No.600, Yishan Road, Xuhui District, Shanghai, 200233, China.

ABSTRACT
Hypoglycemia is a common and serious problem among patients with type 1 diabetes receiving treatment with insulin. Clinical studies have demonstrated that hypoglycemic edema is involved in the initiation of hypoglycemic brain damage. However, the mechanisms of this edema are poorly understood. Vascular endothelial growth factor (VEGF), a potent regulator of blood vessel function, has been observed an important candidate hormone induced by hypoglycemia to protect neurons by restoring plasma glucose. Whether VEGF has a protective effect against hypoglycemia-induced damage in brain endothelial cells is still unknown. To investigate the effects of hypoglycemia on cerebral microvascular endothelial cells and assess the protective effect of exogenous VEGF on endothelial cells during hypoglycemia, confluent monolayers of the brain endothelial cell line bEnd.3 were treated with normal (5.5 mM glucose), hypoglycemic (0, 0.5, 1 mM glucose) medium or hypoglycemic medium in the presence of VEGF. The results clearly showed that hypoglycemia significantly downregulated the expression of claudin-5 in bEnd.3 cells, without affecting ZO-1 and occludin expression and distribution. Besides, transendothelial permeability significantly increased under hypoglycemic conditions compared to that under control conditions. Moreover, the hypoglycemic medium in presence of VEGF decreased endothelial permeability via the inhibition of claudin-5 degradation and improved hypoglycemia-induced cell toxicity. Furthermore, Glucose transporter-1 (Glut-1) and apoptosis regulator Bcl-2 expression were significantly upregulated. Taken together, hypoglycemia can significantly increase paraendocellular permeability by downregulating claudin-5 expression. We further showed that VEGF protected brain endothelial cells against hypoglycemia by enhancing glucose passage, reducing endothelial cell death, and ameliorating paraendocellular permeability.

No MeSH data available.


Related in: MedlinePlus