ERK5 Contributes to VEGF Alteration in Diabetic Retinopathy

Administration of Melatonin in Diabetic Retinopathy Is Effective and Improves the Efficacy of Mesenchymal Stem Cell Treatment

Stem cell transplantation is a promising therapeutic technique for the treatment of a variety of diseases; nevertheless, stem cell therapy may not always work as well as it could. The goal of this study was to test the hypothesis that employing a powerful antioxidant like melatonin improves stem cell transplantation success and potentiates stem cell function in the therapy of diabetic retinopathy. For this purpose, 50 adult male rats were divided into the following: control group: this group received 0.5 ml of 0.1 M of sodium citrate buffer (pH = 4.5) (intraperitoneal (I.P.)). The confirmed diabetic rats were divided into 4 groups: diabetic group: confirmed diabetic rats received no treatments with a regular follow of the blood glucose profile for 8 weeks; melatonin group: confirmed diabetic rats received melatonin (5 mg/kg/day); stem cell group: the confirmed diabetic rats were given intravitreal injection of stem cells (2 μl cell suspension of stem cells (3 × 10⁴ cells/μl)); and melatonin+stem cell group: confirmed diabetic rats received melatonin (5 mg/kg/day), orally once daily for 8 weeks, and 2 μl cell suspension of stem cells (3 × 10⁴ cells/μl) was carefully injected into the vitreous cavity. Our results showed that administration of melatonin and/or stem cell restored the retinal oxidative/antioxidant redox and reduced retinal inflammatory mediators. Coadministration of melatonin and stem cells enhanced the number of transplanted stem cells in the retinal tissue and significantly reduced retinal BDEF, VEGF, APOA1, and RBP4 levels as compared to melatonin and/or stem alone. We may conclude that rats treated with melatonin and stem cells had their retinal oxidative/antioxidant redox values restored to normal and their histological abnormalities reduced. These findings support the hypothesis that interactions with the BDEF, VEGF, APOA1, and RBP4 signaling pathways are responsible for these effects.

PAR1, a therapeutic target for remote lung injury associated with hind limb ischemia/reperfusion: ERK5/KLF2-dependent lung capillary barrier preservation

Protease-activated receptor 1 (PAR1) is expressed in pneumocytes and endothelial cells of the alveolar barrier. Its activation by thrombin disrupts the barrier integrity dynamics and induces lung injury in in vitro and in vivo paradigms. Nonetheless, the role of PAR1, as a therapeutic target, in hind limb ischemia/reperfusion (I/R)-mediated remote lung injury has been unclear. Therefore, this study aimed to determine the potential benefit of PAR1 blockade using the selective antagonist SCH79797 in distant lung dysfunction following hind limb I/R injury with special emphasis on the extracellular signal-regulated kinase 5 (ERK5)/Krüppel-like factor 2 (KLF2) axis. Rats were subdivided into control, bilateral hind limb I/R, SCH79797, and SCH79797+BIX02189 (ERK5 inhibitor) groups. PAR1 blockade, ERK5-dependently, alleviated alveolar barrier disruption as evidenced by reductions in both pulmonary systemic leakage of surfactant protein-D and lung fluid accumulation with increase in pulmonary claudin 5, vascular endothelial cadherin, and connexin 37 levels. Such improvements are downstream targets of the ERK5/KLF2-mediated sphingosine-1-phosphate receptor 1 (S1PR1) upregulated expression and pS536-nuclear factor-κB (NF-κB) p65 inhibition. SCH79797 effectively impedes the evoked inflammatory response and oxidative burst by suppressing vascular endothelial growth factor, tumor necrosis factor-α, lipid peroxidation, and neutrophil infiltration while boosting the glutathione antioxidant defense. Accordingly, PAR1 could be a therapeutic target, where its blockade mitigated pulmonary-endothelial barrier disruption via mutual S1PR1 enhancement and NF-κB p65 inhibition following ERK5/KLF2 activation.

G protein-coupled estrogen receptor regulates the KLF2-dependent eNOS expression by activating of Ca2+ and EGFR signaling pathway in human endothelial cells

G protein-coupled estrogen receptor (GPER) is important for maintaining normal blood vessel function by preventing endothelial cell dysfunction. It has been reported that G-1, an agonist of GPER, increases nitric oxide (NO) production through the phosphorylation of endothelial nitric oxide synthase (eNOS). However, the effect of GPER activation on eNOS expression has not been studied. Our results show that G-1 significantly increased the expression of eNOS and Kruppel-like factor 2 (KLF2) in human endothelial EA.hy926 cells. The individual silences of KLF2 and GPER attenuated G-1-induced eNOS expression. In addition, inhibition of the Gαq and Gβγ suppressed G-1-induced the expression of eNOS and KLF2 in EA.hy926 cells. Interestingly, these effects were similar in HUVECs. Furthermore, we found that GPER-mediated Ca²⁺ signaling increased the phosphorylation of CaMKKβ, AMPK, and CaMKIIα in the cells. The phosphorylation of histone deacetylase 5 (HDAC5) by activation of AMPK and CaMKIIα increased the expression of eNOS via transcriptional activity of KLF2. We further demonstrate that GPER activation increased the phosphorylation of Src, EGFR, ERK5, and MEF2C and consequently induced the expression of eNOS and KLF2. Meanwhile, inhibition of ERK5 and HDAC5 suppressed the expression of eNOS and KLF2 induced by G-1 in the cells. These findings suggest that GPER provides a novel mechanism for understanding the regulation of eNOS expression and is an essential therapeutic target in preventing cardiovascular-related endothelial dysfunction.

Fibroblast-specific ERK5 deficiency changes tumor vasculature and exacerbates tumor progression in a mouse model

The roles of cancer-associated fibroblasts (CAFs) have been studied in the tumor progression, and CAFs are expected to become the new targets for cancer pharmacotherapies. CAFs contribute to tumor cell survival and proliferation, tumor angiogenesis, immune suppression, tumor inflammation, tumor cell invasion and metastasis, and extracellular matrix remodeling. However, detailed mechanisms of how CAFs function in the living system remain unclear. CAFs include α-smooth muscle actin, expressing activated fibroblasts similar to myofibroblasts, and are highly capable of producing collagen. Several reports have demonstrated the contributions of extracellular-signal-regulated kinase 5 (ERK5) in fibroblasts to the fibrotic processes; however, the roles of CAF-derived ERK5 remain unclear. To investigate the roles of CAF-derived ERK5 in the tumor progression, we created mice lacking the ERK5 gene specifically in fibroblasts. Colon-26 mouse colon cancer cells were implanted into the mice subcutaneously, and the histological analyses of the tumor tissue were performed after 2 weeks. Immunofluorescence analyses showed that recipient-derived fibroblasts existed within the tumor tissue. The present study demonstrated that fibroblast-specific ERK5 deficiency exacerbated tumor progression and it was accompanied with thicker tumor vessel formation and the increase in the number of activated fibroblasts. We combined the results of The Cancer Genome Atlas (TCGA) database analysis with our animal studies, and indicated that regulating ERK5 activity in CAFs or CAF invasion into the tumor tissue can be important strategies for the development of new targets in cancer pharmacotherapies.

In vivo studies demonstrate that endothelin-1 traps are a potential therapy for type I diabetes

Background

Type 1 diabetes is a serious, lifelong condition where the body's blood glucose level increases because of the body's inability to make insulin. An important consequence of this is the increased expression of extracellular matrix proteins, such as fibronectin and collagen 4α1, in key tissues and organs like the heart and kidneys. Diabetes is also associated with increased plasma levels of the vasoactive peptide endothelin (ET)-1. This further aggravates the expression of the ECM proteins. There are also important consequences of increased glucose and ET-1 levels in diabetes on the heart, termed diabetic cardiomyopathy.

Methods

We have previously reported the development of ET-traps, which potently and significantly reduce pathological levels of ET-1. In this study, we tested the in vivo therapeutic potential of ET-traps for type 1 diabetes using the B6 mouse model.

Results

Following subcutaneous administration of ET-traps 3 times a week, over a 2 month period, the 500 nM dose of ET-traps gave a significant reduction in collagen 4α1 expression in the heart and kidney, returning it back to control, non-diabetic levels at both the mRNA and protein levels. The expression of fibronectin mRNA is also returned to control levels with the 500 nM dose of ET-traps. The efficacy of ET-traps for type 1 diabetes was further evinced by immunohistochemistry data, echocardiography studies (measuring left ventricular systolic function and diastolic dysfunction) and a measure of urine creatinine and albumin levels. In all analyses, the 500 nM dose of ET-traps returns the different measures to control, non-diabetic levels.

Conclusion

Data from this study show that in a mouse model ET-traps have a potent and significant therapeutic effect on diabetes disease pathology. Future studies could further evaluate the use of ET-traps as a therapy for diabetes, including taking them through clinical trials.

Molecular regulation of ERK5 in development of diabetic retinopathy

Diabetic retinopathy (DR) is a major complication of diabetes, and causes pathological changes in retina blood vessels, as the most common cause of vision loss. Extracellular-signal-regulated kinase 5 (ERK5) is the newest discovered member in the mitogen-activated protein kinases (MAPKs) family, and recent evidence demonstrates an essential role of ERK5 signaling in the angiogenesis. However, whether ERK5 signaling may regulate DR development is unknown. Here, we used a streptozocin (STZ)-induce mouse DR model to investigate this question. We detected significant increases in the phosphorylation of ERK5, a signature of ERK5 activation in the purified retinal endothelial cells in DR mice, compared to control mice. In vivo suppression of ERK5 phosphorylation through administration of a specific inhibitor of ERK5 activation, BIX02189, did not prevent the occurrence of STZ-induced diabetes in mice, but significantly alleviated the severity of DR, seemingly through attenuating the retina neovascularization. Thus, our study suggests a previously unappreciated role of ERK5 signaling in DR development.

miR-146a regulates glucose induced upregulation of inflammatory cytokines extracellular matrix proteins in the retina and kidney in diabetes

Hyperglycemic damage to the endothelial cells (ECs) leads to increased synthesis of inflammatory cytokines. We have previously shown miR-146a downregulation in ECs and in the tissues of diabetic mice. Here we investigated the role of miR-146a, in the production of specific inflammatory cytokines and extracellular matrix (ECM) proteins in retina and kidneys in diabetes. We generated an endothelial specific miR-146a overexpressing transgenic mice (TG). We investigated these mice and wild type (WT) controls with or without streptozotocin (STZ) induced diabetes. Retinal and renal cortical tissues from the mice were examined for mRNAs for specific inflammatory markers, (ECM) proteins and inflammation inducible transcription factor by real time RT-PCR. Corresponding proteins, where possible, were examined using immunofluorescence or ELISA. In parallel, we examined ECs following incubation with various levels of glucose with or without miR-146a mimic transfection. In the retina and kidneys of WT mice with diabetes, increased expression of inflammatory markers (IL-6, TNFα, IL1β) in association augmented expression of ECM proteins (collagen 1αIV, fibronectin) and NF κB-P65 were observed, compared to WT non-diabetic controls. These changes were prevented in diabetic miR-146a TG mice along with retinal and renal functional and structural changes. In vitro studies showed similar changes in the ECs exposed to high glucose. Such changes were corrected in the cells following miR-146a mimic transfection. Further analyses of renal cortical tissues showed diabetes induced significant upregulation of two regulators of NFκB, namely Interleukin-1 associated Kinase 1 and tumour necrosis factor receptor associated factor. Such changes were prevented in diabetic TG animals. These data indicate that augmented production of inflammatory cytokines and ECM proteins in the retina and kidneys in diabetes are regulated through endothelium derived miR-146a. Identification of such novel mechanisms may potentially lead to the development of novel therapies.

Targeting MAPK Signaling in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a major cause of irreversible blindness affecting elderly people in the world. AMD is a complex multifactorial disease associated with demographic, genetics, and environmental risk factors. It is well established that oxidative stress, inflammation, and apoptosis play critical roles in the pathogenesis of AMD. The mitogen-activated protein kinase (MAPK) signaling pathways are activated by diverse extracellular stimuli, including growth factors, mitogens, hormones, cytokines, and different cellular stressors such as oxidative stress. They regulate cell proliferation, differentiation, survival, and apoptosis. This review addresses the novel findings from human and animal studies on the relationship of MAPK signaling with AMD. The use of specific MAPK inhibitors may represent a potential therapeutic target for the treatment of this debilitating eye disease.

ERK5 Mediated Signalling in Diabetic Retinopathy

Diabetic retinopathy is the lead among causes of blindness in North America. Glucose-induced endothelial injury is the most important cause of diabetic retinopathy and other vascular complications. Extracellular signal-regulated kinase 5 (ERK5), also known as big mitogen-activated protein kinase 1 (BMK1), is a member of mitogen-activated protein kinases (MAPK) family. Physiologically, it is critical for cardiovascular development and maintenance of the endothelial cell integrity. Extracellular signal-regulated kinase 5 is protective for endothelial cells under stimulation and stress. Decreased activation of ERK5 results in increased endothelial cell death. Extracellular signal-regulated kinase 5 signaling may be subject to alteration by hyperglycemia, while signaling pathway including ERK5 may be subject to alteration during pathogenesis of diabetic complications. In this review, the role of ERK5 in diabetic macro- and microvascular complications with a focus on diabetic retinopathy are summarized and discussed.

Elevated cell proliferation and VEGF production by high-glucose conditions in Müller cells involve XIAP

PURPOSE

Müller cells have important roles in the pathogenesis of diabetic retinopathy by promoting cell proliferation and inducing the production of vascular endothelial growth factor (VEGF) under hyperglycemic conditions. The objective of this study was to determine the potential mechanism of Müller cell proliferation and VEGF production due to high-glucose conditions.

METHODS

Primary cultured rat Müller cells were incubated with medium containing variable concentrations of glucose and/or embelin, a specific inhibitor of X-linked inhibitor of apoptosis protein (XIAP), for 72 h. The proliferation of Müller cells was assessed by the MTT assay. The expression and/or phosphorylation of 146 proteins were assessed using protein pathway array.

RESULTS

High concentrations of glucose-induced Müller cell proliferation and altered expression and/or phosphorylation of 47 proteins that have been identified to have key roles in several important signaling pathways (XIAP, VEGF, HIF1α, NFκB, etc) and are involved in the regulation of cell survival, proliferation, or apoptosis. However, Müller cell alterations induced by high-glucose conditions were counteracted by the XIAP inhibitor embelin, and 26 proteins/phosphorylations (out of 47) were restored to their normal levels. Nine proteins, including NFκB p65, p-p38, tumor necrosis factor-α, urokinase-type plasminogen activator, CREB, IL-1β, HCAM, estrogen receptor-α, and p-Stat3, were involved in regulatory networks between XIAP and VEGF.

CONCLUSIONS

The current study suggests that XIAP may be a potential regulator that can mediate a series of pathological changes induced by high-glucose conditions in Müller cells. Therefore, embelin could be a potential agent for the prevention and treatment of diabetic retinopathy.

The effect of vascular endothelial growth factor in the progression of bladder cancer and diabetic retinopathy

Bladder cancer and diabetic retinopathy is a major public health and economical burden worldwide. Despite its high prevalence, the molecular mechanisms that induce or develop bladder carcinomas and diabetic retinopathy progression are poorly understood but it might be due to the disturbance in balance between angiogenic factors such as VEGF and antiangiogenic factors such as pigment epithelium derived growth factor. VEGF is one of the important survival factors for endothelial cells in the process of normal physiological and abnormal angiogenesis and induce the expression of antiapoptotic proteins in the endothelial cells. It is also the major initiator of angiogenesis in cancer and diabetic retinopathy, where it is up-regulated by oncogenic expression and different type of growth factors. The alteration in VEGF and VEGF receptors gene and overexpression, determines a diseases phenotype and ultimately the patient's clinical outcome. However, expressional and molecular studies were made on VEGF to understand the exact mechanism of action in the genesis and progression of bladder carcinoma and diabetic retinopathy , but still how VEGF mechanism involve in such type of disease progression are not well defined. Some other factors also play a significant role in the process of activation of VEGF pathways. Therefore, further detailed analysis via molecular and therapeutic is needed to know the exact mechanisms of VEGF in the angiogenesis pathway. The detection of these types of diseases at an early stage, predict how it will behave and act in response to treatment through regulation of VEGF pathways. The present review aimed to summarize the mechanism of alteration of VEGF gene pathways, which play a vital role in the development and progression of bladder cancer and diabetic retinopathy.