Endothelin-1, over-expressed in SOD1G93A mice, aggravates injury of NSC34-hSOD1G93A cells through complicated molecular mechanism revealed by quantitative proteomics analysis

Endothelin-1 (ET-1), a secreted signaling peptide, is suggested to be involved in multiple actions in various tissues including the brain, but its role in amyotrophic lateral sclerosis (ALS) remains unknown. In this study, we detected the expression changes as well as the cellular localization of ET-1, endothelin A (ET-A) and endothelin B (ET-B) receptors in spinal cord of transgenic SOD1-G93A (TgSOD1-G93A) mice, which showed that the two ET receptors (ET-Rs) expressed mainly on neurons and decreased as the disease progressed especially ET-B, while ET-1 expression was up-regulated and primarily localized on astrocytes. We then explored the possible mechanisms underlying the effect of ET-1 on cultured NSC34-hSOD1G93A cell model. ET-1 showed toxic effect on motor neurons (MNs), which can be rescued by the selective ET-A receptor antagonist BQ-123 or ET-B receptor antagonist BQ-788, suggesting that clinically used ET-Rs pan-antagonist could be a potential strategy for ALS. Using proteomic analysis, we revealed that 110 proteins were differentially expressed in NSC34-hSOD1G93A cells after ET-1 treatment, of which 54 were up-regulated and 56 were down-regulated. Bioinformatic analysis showed that the differentially expressed proteins (DEPs) were primarily enriched in hippo signaling pathway-multiple species, ABC transporters, ErbB signaling pathway and so on. These results provide further insights on the potential roles of ET-1 in ALS and present a new promising therapeutic target to protect MNs of ALS.

Drug repurposing for vascular dementia: overview and current developments

Antidementive drugs have made Alzheimer's disease a symptomatically treatable condition but have essentially bypassed vascular dementia. The complexity of its pathology, the variable pathognomonic manifestations, the absence of validated biomarkers and the continuum with Alzheimer's disease that makes vascular dementia a comparatively small market are the major contributing factors. This report discusses how drug repurposing can be harnessed to identify new therapeutic opportunities, where such efforts are already yielding promising results, and which ones must be considered failures. Most investigations address obvious aspects cerebral small vessel disease, but some early-stage developments attempt changes in gene expression or modulation of complex biological pathways. A stronger focus on the nature and dynamics of white matter lesions should yield additional molecular targets.

Cerebral hypoperfusion and glucose hypometabolism: Key pathophysiological modulators promote neurodegeneration, cognitive impairment, and Alzheimer's disease

Aging, hypertension, diabetes, hypoxia/obstructive sleep apnea (OSA), obesity, vitamin B12/folate deficiency, depression, and traumatic brain injury synergistically promote diverse pathological mechanisms including cerebral hypoperfusion and glucose hypometabolism. These risk factors trigger neuroinflammation and oxidative-nitrosative stress that in turn decrease nitric oxide and enhance endothelin, Amyloid-β deposition, cerebral amyloid angiopathy, and blood-brain barrier disruption. Proinflammatory cytokines, endothelin-1, and oxidative-nitrosative stress trigger several pathological feedforward and feedback loops. These upstream factors persist in the brain for decades, upregulating amyloid and tau, before the cognitive decline. These cascades lead to neuronal Ca²⁺ increase, neurodegeneration, cognitive/memory decline, and Alzheimer's disease (AD). However, strategies are available to attenuate cerebral hypoperfusion and glucose hypometabolism and ameliorate cognitive decline. AD is the leading cause of dementia among the elderly. There is significant evidence that pathways involving inflammation and oxidative-nitrosative stress (ONS) play a key pathophysiological role in promoting cognitive dysfunction. Aging and several comorbid conditions mentioned above promote diverse pathologies. These include inflammation, ONS, hypoperfusion, and hypometabolism in the brain. In AD, chronic cerebral hypoperfusion and glucose hypometabolism precede decades before the cognitive decline. These comorbid disease conditions may share and synergistically activate these pathophysiological pathways. Inflammation upregulates cerebrovascular pathology through proinflammatory cytokines, endothelin-1, and nitric oxide (NO). Inflammation-triggered ONS promotes long-term damage involving fatty acids, proteins, DNA, and mitochondria; these amplify and perpetuate several feedforward and feedback pathological loops. The latter includes dysfunctional energy metabolism (compromised mitochondrial ATP production), amyloid-β generation, endothelial dysfunction, and blood-brain-barrier disruption. These lead to decreased cerebral blood flow and chronic cerebral hypoperfusion- that would modulate metabolic dysfunction and neurodegeneration. In essence, hypoperfusion deprives the brain from its two paramount trophic substances, viz., oxygen and nutrients. Consequently, the brain suffers from synaptic dysfunction and neuronal degeneration/loss, leading to both gray and white matter atrophy, cognitive dysfunction, and AD. This Review underscores the importance of treating the above-mentioned comorbid disease conditions to attenuate inflammation and ONS and ameliorate decreased cerebral blood flow and hypometabolism. Additionally, several strategies are described here to control chronic hypoperfusion of the brain and enhance cognition. © 2016 Wiley Periodicals, Inc.

Cytokines and growth factors modify the upregulation of contractile endothelin ET(A) and ET(B) receptors in rat cerebral arteries after organ culture

AIM

Experimental cerebral ischaemia and organ culture of cerebral arteries induce an increased endothelin ET(B) receptor-mediated contraction. The aim of this study was to examine whether cytokines and growth factors, known to be activated in ischaemia, can influence the expression and function of endothelin receptors after organ culture.

METHODS

Rat middle cerebral arteries were cultured for 24 h at 37 °C in humidified 5% CO(2) and air in culture medium alone, or with tumour necrosis factor-α (TNF-α), interleukin-1β (IL-1β), platelet-derived growth factor (PDGF), epidermal growth factor (EGF) or basic fibroblast growth factor (bFGF). Concentration-response curves were obtained for sarafotoxin 6c (ET(B) receptor agonist) and endothelin-1 (here ET(A) receptor agonist, because of ET(B) receptor desensitization). The receptor mRNA expression was examined by real-time PCR and the protein expression by immunohistochemistry and Western blot.

RESULTS

Tumour necrosis factor-α (100 ng mL(-1) ) and EGF (20 ng mL(-1) ) potentiated the ET(B) receptor-mediated contraction (increase in pEC(50) without change in E(max) ). bFGF (10 ng mL(-1) ) and IL-1β (10 ng mL(-1) ) induced an enhanced ET(A) receptor-mediated contraction. bFGF (10 ng mL(-1) ) significantly increased the ET(B) mRNA level, and EGF (20 ng mL(-1) ) increased the ET(A) receptor protein. Increased ET(B) receptor mRNA and protein level also were observed after treatment with IL-1β (10 ng mL(-1) ).

CONCLUSION

This study shows that TNF-α, IL-1β, EGF and bFGF can modify the expression and function of endothelin receptors during organ culture. Because there is similar receptor upregulation in experimental stroke, the effect of cytokines and growth factors on endothelin receptor upregulation is an interesting aspect to study in vivo.