Characterization of activation of MAP kinase superfamily in vasculature from diabetic rats

Glucagon-like peptide-1 receptor agonist reduces di(2-ethylhexyl) phthalate-induced atherosclerotic processes in vascular smooth muscle cells

Glucagon-like peptide-1 receptor (GLP1R) agonist is an incretin hormone and regulates glucose metabolism. However, phthalates, known as endocrine disruptors, can interfere with hormone homeostasis. In the present study, we aimed to estimate the impact of GLP1R agonist on di(2 ethylhexyl) phthalate (DEHP)-induced atherosclerosis. For this purpose, the effects of GLP1R agonist on various atherogenesis-related cellular processes and pathways were assessed in vascular smooth muscle cells (VSMCs). DEHP-induced cell proliferation and migration were significantly decreased by GLP1R agonist in VSMCs. Protein levels of matrix metalloproteinase (MMP)-2 and MMP-9 were significantly decreased in cells exposed to GLP1R agonist, compared with DEHP-treated cells. Expression levels of intercellular adhesion molecule 1 and vascular cell adhesion molecule 1 were also reduced in GLP1R agonist-treated cells. Similarly, DEHP-associated phosphorylation of protein kinase B and extracellular signal-regulated kinase 1/2 was decreased in GLP1R agonist-treated cells, compared with DEHP-treated cells. Our findings suggest that treatment with GLP1R agonist counteracts the activation of pathways related to atherosclerosis.

Hyperglycemia-impaired aortic vasorelaxation mediated through arginase elevation: Role of stress kinase pathways

Diabetes-induced vascular endothelial dysfunction has been reported to involve hyperglycemia-induced increases in arginase activity. However, upstream mediators of this effect are not clear. Here, we have tested involvement of Rho kinase, ERK1/2 and p38 MAPK pathways in this process. Studies were performed with aortas isolated from wild type or hemizygous arginase 1 knockout (Arg1^+/-) mice and bovine aortic endothelial cells exposed to high glucose (HG, 25 mmol/l) or normal glucose (NG, 5.5 mmol/l) conditions for different times. Effects of inhibitors of arginase, p38 MAPK, ERK1/2 or ROCK and ex vivo adenoviral delivery of active Arg1 and inactive (D128-Arg1) cDNA were also determined. Exposure in wild type aorta or endothelial cells to HG significantly increased arginase activity and Arg1 expression and impaired aortic relaxation. Transduction of wild type aorta with active Arg1 cDNA impaired vascular relaxation, whereas inactive Arg1 had no effect. The HG-induced vascular endothelial dysfunction was associated with increased phosphorylation (activation) of ERK1/2 and p38 MAPK. Pretreatment with inhibitors of ERK1/2, p38 MAPK, ROCK or arginase blocked HG-induced elevation of arginase activity and Arg1 expression and prevented the vascular dysfunction. Inhibition of ROCK blunted the HG-induced activation of ERK1/2 and p38 MAPK. In summary, activated ROCK and subsequent activation of ERK1/2 or p38 MAPK elevates arginase activity and Arg1 expression in hyperglycemic states. Targeting this pathway may provide an effective means for preventing diabetes/hyperglycemia-induced vascular endothelial dysfunction.

Exogenous H2S modulates mitochondrial fusion-fission to inhibit vascular smooth muscle cell proliferation in a hyperglycemic state

Aim

Vascular smooth muscle cell (VSMC) proliferation in response to hyperglycemia is an important process in the development of arterial vessel hyperplasia. The shape change of mitochondria is dynamic and closely related to fission and fusion. Hydrogen sulfide (H₂S) was confirmed to have anti-oxidative, anti-inflammatory and anti-proliferative effects. However, little it is known about its effects on mitochondrial morphology induced by hyperglycemia. The aim of the study is to demonstrate that H₂S inhibits VSMC proliferation through regulating mitochondrial fission.

Methods and results

We observe lower H₂S levels as well as higher proliferative protein expression levels for proliferative cell nuclear antigen (PCNA) and cyclin D1 and higher mitochondrial fusion–fission protein expression levels for dynamin-related protein 1 (Drp 1) in human kidney arteries and in db/db mouse aorta. Exogenous H₂S (100 μM NaHS) inhibits vascular smooth muscle cells of human pulmonary aorta(HPASMC) proliferation and migration in response to high glucose using the BrdU and scratch wound repair assays, decreases proliferative protein (PCNA and cyclin D1) expression, and reduces ROS production in the cytoplasm and mitochondria. When HPASMCs proliferate with a high glucose treatment, the mitochondria become small spheres with a short rod-shaped structure, whereas NaHS, a mitochondrial division inhibitor and siDrp prevent VSMC proliferation and maintain mitochondria as stationary and randomly dispersed with fixed structures.

Conclusion

Exogenous H₂S aids in inhibiting mitochondrial fragmentation and affects proliferation in db/db mice and HPASMCs by decreasing Drp 1 expression.

Electronic supplementary material

The online version of this article (doi:10.1186/s13578-016-0102-x) contains supplementary material, which is available to authorized users.

Gallic acid ameliorates renal functions by inhibiting the activation of p38 MAPK in experimentally induced type 2 diabetic rats and cultured rat proximal tubular epithelial cells

Diabetic nephropathy (DN) is one of the leading causes of morbidity and mortality in diabetic patients that accounts for about 40% of deaths in type 2 diabetes. p38 mitogen activated protein kinase (p38 MAPK), a serine-threonine kinase, plays an important role in tissue inflammation and is known to be activated under conditions of oxidative stress and hyperglycemia. The role of p38 MAPK has been demonstrated in DN, and its inhibition has been suggested as an alternative approach in the treatment of DN. In the present study, we investigated the nephroprotective effects of an anti-inflammatory phenolic compound, gallic acid (GA, 3,4,5-trihydroxybenzoic acid), in high fat diet/streptozotocin (HFD/STZ) induce type 2 diabetic wistar albino rats. GA (25 mg/kgbw and 50 mg/kgbw, p.o.) treatment for 16 weeks post induction of diabetes led to a significant reduction in the levels of blood glucose, HbA1c, serum creatinine, blood urea nitrogen and proteinuria as well as a significant reduction in the levels of creatinine clearance. GA significantly inhibited the renal p38 MAPK and nuclear factor kappa B (N-κB) activation as well as significantly reduced the levels of renal transforming growth factor beta (TGF-β) and fibronectin. Treatment with GA resulted in a significant reduction in the serum levels of proinflammatory cytokines viz. interleukin 1 beta (IL-1β), IL-6 and tumor necrosis factor alpha (TNF-α). Moreover, GA significantly lowered renal pathology and attenuated renal oxidative stress. In cultured rat NRK 52E proximal tubular epithelial cells, GA treatment inhibited high glucose induced activation of p38 MAPK and NF-κB as well as suppressed proinflammatory cytokine synthesis. The results of the present study provide in vivo and in vitro evidences that the p38 MAPK pathway plays an important role in the pathogenesis of DN, and GA attenuates the p38 MAPK-mediated renal dysfunction in HFD/STZ induced type 2 diabetic rats.

Liraglutide attenuates high glucose-induced abnormal cell migration, proliferation, and apoptosis of vascular smooth muscle cells by activating the GLP-1 receptor, and inhibiting ERK1/2 and PI3K/Akt signaling pathways

Background

As a new anti-diabetic medicine, Liraglutide (LIRA), one of GLP-1 analogues, has been found to have an anti-atherosclerotic effect. Since vascular smooth muscle cells (VSMCs) play pivotal roles in the occurrence of diabetic atherosclerosis, it is important to investigate the role of LIRA in reducing the harmful effects of high-glucose (HG) treatment in cultured VSMCs, and identifying associated molecular mechanisms.

Methods

Primary rat VSMCs were exposed to low or high glucose-containing medium with or without LIRA. They were challenged with HG in the presence of phosphatidylinositol 3-kinase (PI3K), extracellular signal-regulated kinase (ERK)1/2, or glucagon-like peptide receptor (GLP-1R) inhibitors. Cell proliferation and viability was evaluated using a Cell Counting Kit-8. Cell migration was determined by Transwell migration and scratch wound assays. Flow cytometry and Western blotting were used to determine apoptosis and protein expression, respectively.

Results

Under the HG treatment, VSMCs exhibited increased migration, proliferation, and phosphorylation of protein kinase B (Akt) and ERK1/2, along with reduced apoptosis (all p < 0.01 vs. control). These effects were significantly attenuated with LIRA co-treatment (all p < 0.05 vs. HG alone). Inhibition of PI3K kinase and ERK1/2 similarly attenuated the HG-induced effects (all p < 0.01 vs. HG alone). GLP-1R inhibitors effectively reversed the beneficial effects of LIRA on HG treatment (all p < 0.05).

Conclusions

HG treatment may induce abnormal phenotypes in VSMCs via PI3K and ERK1/2 signaling pathways activated by GLP-1R, and LIRA may protect cells from HG damage by acting on these same pathways.

Vinpocetine attenuates neointimal hyperplasia in diabetic rat carotid arteries after balloon injury

BACKGROUND

Diabetes exacerbates abnormal vascular smooth muscle cell (VSMC) accumulation in response to arterial wall injury. Vinpocetine has been shown to improve vascular remolding; however, little is known about the direct effects of vinpocetine on vascular complications mediated by diabetes. The objective of this study was to determine the effects of vinpocetine on hyperglycemia-facilitated neointimal hyperplasia and explore its possible mechanism.

MATERIALS AND METHODS

Nondiabetic and diabetic rats were subjected to balloon injury of the carotid artery followed by 3-week treatment with either vinpocetine (10 mg/kg/day) or saline. Morphological analysis and proliferating cell nuclear antigen (PCNA) immunostaining were performed on day 21. Rat VSMCs proliferation was determined with 5-ethynyl-20-deoxyuridine cell proliferation assays. Chemokinesis was monitored with scratch assays, and production of reactive oxygen species (ROS) was assessed using a 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA) flow cytometric assay. Apoptosis was detected by annexin V-FITC/PI flow cytometric assay. Cell signaling was assessed by immunblotting.

RESULTS

Vinpocetine prevented intimal hyperplasia in carotid arteries in both normal (I/M ratio: 93.83 ± 26.45% versus 143.2 ± 38.18%, P<0.05) and diabetic animals (I/M ratio: 120.5 ± 42.55% versus 233.46 ± 33.98%, P<0.05) when compared to saline. The in vitro study demonstrated that vinpocetine significantly inhibited VSMCs proliferation and chemokinesis as well as ROS generation and apoptotic resistance, which was induced by high glucose (HG) treatment. Vinpocetine significantly abolished HG-induced phosphorylation of Akt and JNK1/2 without affecting their total levels. For downstream targets, HG-induced phosphorylation of IκBα was significantly inhibited by vinpocetine. Vinpocetine also attenuated HG-enhanced expression of PCNA, cyclin D1 and Bcl-2.

CONCLUSIONS

Vinpocetine attenuated neointimal formation in diabetic rats and inhibited HG-induced VSMCs proliferation, chemokinesis and apoptotic resistance by preventing ROS activation and affecting MAPK, PI3K/Akt, and NF-κB signaling.

Proteome-based systems biology analysis of the diabetic mouse aorta reveals major changes in fatty acid biosynthesis as potential hallmark in diabetes mellitus-associated vascular disease

BACKGROUND

Macrovascular complications of diabetes mellitus are a major risk factor for cardiovascular morbidity and mortality. Currently, studies only partially described the molecular pathophysiology of diabetes mellitus-associated effects on vasculature. However, better understanding of systemic effects is essential in unraveling key molecular events in the vascular tissue responsible for disease onset and progression.

METHODS AND RESULTS

Our overall aim was to get an all-encompassing view of diabetes mellitus-induced key molecular changes in the vasculature. An integrative proteomic and bioinformatics analysis of data from aortic vessels in the low-dose streptozotocin-induced diabetic mouse model (10 animals) was performed. We observed pronounced dysregulation of molecules involved in myogenesis, vascularization, hypertension, hypertrophy (associated with thickening of the aortic wall), and a substantial reduction of fatty acid storage. A novel finding is the pronounced downregulation of glycogen synthase kinase-3β (Gsk3β) and upregulation of molecules linked to the tricarboxylic acid cycle (eg, aspartate aminotransferase [Got2] and hydroxyacid-oxoacid transhydrogenase [Adhfe1]). In addition, pathways involving primary alcohols and amino acid breakdown are altered, potentially leading to ketone-body production. A number of these findings were validated immunohistochemically. Collectively, the data support the hypothesis that in this diabetic model, there is an overproduction of ketone-bodies within the vessels using an alternative tricarboxylic acid cycle-associated pathway, ultimately leading to the development of atherosclerosis.

CONCLUSIONS

Streptozotocin-induced diabetes mellitus in animals leads to a reduction of fatty acid biosynthesis and an upregulation of an alternative ketone-body formation pathway. This working hypothesis could form the basis for the development of novel therapeutic intervention and disease management approaches.

Vaspin attenuates high glucose-induced vascular smooth muscle cells proliferation and chemokinesis by inhibiting the MAPK, PI3K/Akt, and NF-κB signaling pathways

BACKGROUND

Vaspin has insulin-sensitizing effects, as well as additional beneficial effects on metabolic diseases. However, little is known about the direct effects of vaspin on vascular complications mediated by diabetes. The objective of this study is to determine the efficacy and mechanism of vaspin on hyperglycemia-induced vascular smooth muscle cells (VSMCs) proliferation, chemokinesis and cell signaling.

METHODS

Rat VSMCs proliferation was determined with 5-ethynyl-2'-deoxyuridine cell proliferation assays, chemokinesis was monitored with scratch assays, and reactive oxygen species (ROS) production was assessed using H2DCFDA and SOD-inhibited reduction of ferricytochrome c assay. Luciferase activity is assayed using a Dual Luciferase Reporter Assay System. Cell signaling is assessed by immunoblotting.

RESULTS

Vaspin significantly inhibited VSMCs proliferation and chemokinesis, as well as ROS generation and NADPH oxidase activity, induced by high glucose (HG) treatment. Compared with HG, vaspin significantly decreased VSMCs proliferation by 40 ± 8% at 100 ng/ml. Vaspin also decreased ROS production by 16 ± 8% at 100 ng/ml and 30 ± 8% at 300 ng/ml (all P < 0.01). Vaspin significantly abolished HG-induced phosphorylation of oxidase subunits p47phox, Akt, p38, and JNK1/2 without affecting their total levels, and attenuated HG-induced phosphorylation of insulin receptor and its downstream IRS-1 and IRS-2. For downstream targets, NF-κB activity and IκBα phosphorylation were both enhanced significantly after HG stimulation, and these effects were inhibited by vaspin. Vaspin also significantly abolished HG-induced PCNA and cyclin D1 expression.

CONCLUSIONS

Vaspin inhibits HG-induced VSMCs proliferation and chemokinesis by preventing ROS activation and MAPK, PI3K/Akt, and NF-κB signaling.

Mechanisms of diabetic complications

It is increasingly apparent that not only is a cure for the current worldwide diabetes epidemic required, but also for its major complications, affecting both small and large blood vessels. These complications occur in the majority of individuals with both type 1 and type 2 diabetes. Among the most prevalent microvascular complications are kidney disease, blindness, and amputations, with current therapies only slowing disease progression. Impaired kidney function, exhibited as a reduced glomerular filtration rate, is also a major risk factor for macrovascular complications, such as heart attacks and strokes. There have been a large number of new therapies tested in clinical trials for diabetic complications, with, in general, rather disappointing results. Indeed, it remains to be fully defined as to which pathways in diabetic complications are essentially protective rather than pathological, in terms of their effects on the underlying disease process. Furthermore, seemingly independent pathways are also showing significant interactions with each other to exacerbate pathology. Interestingly, some of these pathways may not only play key roles in complications but also in the development of diabetes per se. This review aims to comprehensively discuss the well validated, as well as putative mechanisms involved in the development of diabetic complications. In addition, new fields of research, which warrant further investigation as potential therapeutic targets of the future, will be highlighted.

Growth factor and cytokine interactions in myogenesis. Part II. Expression of IGF binding proteins and protein kinases essential for myogenesis in mouse C2C12 myogenic cells exposed to TNF-α and IFN-γ

The aim of the study was to examine potential interactions among IGF-I and proinflammatory cytokines, TNF-α and IFN-γ, in the regulation of local IGF-I bioavailability and cellular proteins mediating myogenic signals. We investigated levels of IGFBP-4, -5, -6, protein kinase Czeta (PKCζ), p38 and extracellular signal-regulated kinase (ERK1/2) in differentiating mouse C2C12 myoblasts. IGF-I significantly stimulated expression of IGFBP-5. TNF-α and IFN-γ attenuated the expression of IGFBP-4 and -6 under basal conditions and in the presence of IGF-I, and inhibited IGF-I-induced IGFBP-5 expression during 5-day myogenesis. TNF-α and IFN-γ markedly attenuated p38 expression in the presence of IGF-I on the 5th day of myogenesis. When combined with IGF-I the cytokines exerted opposite effects on the PKCζ level, i.e. TNF-α caused an increase, whereas IFN-γ reduced the cellular content of this kinase. Exposition of C2C12 myoblasts to IGF-I or cytokines led to the stimulation of ERK1/2 phosphorylation; however, both TNF-α and IFN-γ exerted an inhibitory effect on the activation of ERK1/2 in myoblasts cultured in the presence of IGF-I. We concluded as follows: i) TNF-α and IFN-γ present in the extracellular environment of differentiating C2C12 myoblasts can alter the local bioavailability of IGF-I by inhibiting the expression of IGFBP-4, -5, and -6, ii) the decrease in p38 expression and ERK1/2 phosphorylation in C2C12 myoblasts exposed to cytokines can lead to disturbances in IGF-I-regulated myogenesis.

Grape seed proanthocyanidins attenuate vascular smooth muscle cell proliferation via blocking phosphatidylinositol 3-kinase-dependent signaling pathways

The excess generation of reactive oxygen species (ROS) play important role in the development and progression of diabetes and related vascular complications. Therefore, blocking the production of ROS will be able to improve hyperglycemia-induced vascular dysfunction. The objective of this study was to determine whether a novel IH636 grape seed proanthocyanidins (GSPs) could protect against hyperproliferation of cultured rat vascular smooth muscle cells (VSMCs) induced by high glucose (HG) and determine the related molecular mechanisms. Our data demonstrated that GSPs markedly inhibited rat VSMCs proliferation as well as ROS generation and NAPDH oxidase activity induced by HG treatment. Further studies revealed that HG treatment resulted in phosphorylation and membrane translocation of Rac1, p47phox, and p67phox subunits leading to NADPH oxidase activation. GSPs treatment remarkably disrupted the phosphorylation and membrane translocation of Rac1, p47phox, and p67phox subunits. More importantly, our data further revealed that GSPs significantly disrupted HG-induced activation of ERK1/2, JNK1/2, and PI3K/AKT/GSK3beta as well as NF-kappaB signalings, which were dependent on reactive oxygen species (ROS) generation and Rac1 activation. In addition, our results also demonstrated that HG-induced cell proliferation and excess ROS production was dependent on the activation of PI3 kinase subunit p110alpha. Collectively, these results suggest that HG-induced VSMC growth was attenuated by grape seed proanthocyanidin (GSPs) treatment through blocking PI3 kinase-dependent signaling pathway, indicating that GSPs may be useful in retarding intimal hyperplasia and restenosis in diabetic vessels.

Effects of p38 MAPK inhibition on early stages of diabetic retinopathy and sensory nerve function

Purpose. p38 mitogen-activated protein kinase (MAPK) is known to play a regulatory role in inflammatory processes in disease. Inflammation has been linked also to the development of diabetic retinopathy in rodents. This study was conducted to evaluate the effect of a p38 MAPK inhibitor on the development of early stages of diabetic retinopathy in rats. Methods. Streptozotocin-diabetic rats were assigned to two groups-treated with the p38 MAPK inhibitor PHA666859 (Pfizer, New York, NY) and untreated-and compared with age-matched nondiabetic control animals. Results. At 2 months of diabetes, insulin-deficient diabetic control rats exhibited significant increases in retinal superoxide, nitric oxide (NO), cyclooxygenase (COX)-2, and leukostasis within retinal microvessels. All these abnormalities were significantly inhibited by the p38 MAPK inhibitor (25 mg/kgBW/d). At 10 months of diabetes, significant increases in the number of degenerate (acellular) capillaries and pericyte ghosts were measured in control diabetic rats versus those in nondiabetic control animals, and pharmacologic inhibition of p38 MAPK significantly inhibited all these abnormalities (all P < 0.05). This therapy also had beneficial effects outside the eye in diabetes, as evidenced by the inhibition of a diabetes-induced hypersensitivity of peripheral nerves to light touch (tactile allodynia). Conclusions. p38 MAPK plays an important role in diabetes-induced inflammation in the retina, and inhibition of p38 MAPK offers a novel therapeutic approach to inhibiting the development of early stages of diabetic retinopathy and other complications of diabetes.