Role of poly(ADP-ribose) polymerase-1 activation in the pathogenesis of diabetic complications: endothelial dysfunction, as a common underlying theme

Integrated approach to reducing polypharmacy in older people: exploring the role of oxidative stress and antioxidant potential therapy

Increased life expectancy, attributed to improved access to healthcare and drug development, has led to an increase in multimorbidity, a key contributor to polypharmacy. Polypharmacy is characterised by its association with a variety of adverse events in the older persons. The mechanisms involved in the development of age-related chronic diseases are largely unknown; however, altered redox homeostasis due to ageing is one of the main theories. In this context, the present review explores the development and interaction between different age-related diseases, mainly linked by oxidative stress. In addition, drug interactions in the treatment of various diseases are described, emphasising that the holistic management of older people and their pathologies should prevail over the individual treatment of each condition.

Dapagliflozin suppresses diabetes-induced oxidative DNA damage and hypermethylation in mouse somatic cells

Diabetes mellitus is a complex metabolic disorder resulting from the interplay of environmental, genetic, and epigenetic factors that increase the risk of cancer development. However, it is unclear whether the increased cancer risk is due to poor glycemic control or the use of some antidiabetic medications. Therefore, we investigated the genetic and epigenetic changes in somatic cells in a mouse model of diabetes and studied whether multiple exposures to the antidiabetic medication dapagliflozin influence these changes. We also elucidated the mechanism(s) of these ameliorations. The micronucleus test and modified comet assay were used to investigate bone marrow DNA damage and methylation changes. These assays revealed that dapagliflozin is non-genotoxic in the tested regimen, and oxidative DNA damage and hypermethylation were significantly higher in diabetic mice. Spectrophotometry also evaluated oxidative DNA damage and global DNA methylation, revealing similar significant alterations induced by diabetes. Conversely, the dapagliflozin-treated diabetic animals significantly reduced these changes. The expression of some genes involved in DNA repair and DNA methylation was disrupted considerably in the somatic cells of diabetic animals. In contrast, dapagliflozin treatment significantly restored these disruptions and enhanced DNA repair. The simultaneous effects of decreased oxidative DNA damage and hypermethylation levels suggest that dapagliflozin can be used as a safe antidiabetic drug to reduce DNA damage and hypermethylation in diabetes, demonstrating its usefulness in patients with diabetes to control hyperglycemia and decrease the development of its subsequent complications.

Glucose transport, transporters and metabolism in diabetic retinopathy

Diabetic retinopathy (DR) is the most common reason for blindness in working-age individuals globally. Prolonged high blood glucose is a main causative factor for DR development, and glucose transport is prerequisite for the disturbances in DR caused by hyperglycemia. Glucose transport is mediated by its transporters, including the facilitated transporters (glucose transporter, GLUTs), the "active" glucose transporters (sodium-dependent glucose transporters, SGLTs), and the SLC50 family of uniporters (sugars will eventually be exported transporters, SWEETs). Glucose transport across the blood-retinal barrier (BRB) is crucial for nourishing the neuronal retina in the context of retinal physiology. This physiological process primarily relies on GLUTs and SGLTs, which mediate the glucose transportation across both the cell membrane of retinal capillary endothelial cells and the retinal pigment epithelium (RPE). Under diabetic conditions, increased accumulation of extracellular glucose enhances the retinal cellular glucose uptake and metabolism via both glycolysis and glycolytic side branches, which activates several biochemical pathways, including the protein kinase C (PKC), advanced glycation end-products (AGEs), polyol pathway and hexosamine biosynthetic pathway (HBP). These activated biochemical pathways further increase the production of reactive oxygen species (ROS), leading to oxidative stress and activation of Poly (ADP-ribose) polymerase (PARP). The activated PARP further affects all the cellular components in the retina, and finally resulting in microangiopathy, neurodegeneration and low-to-moderate grade inflammation in DR. This review aims to discuss the changes of glucose transport, glucose transporters, as well as its metabolism in DR, which influences the retinal neurovascular unit (NVU) and implies the possible therapeutic strategies for treating DR.

HIF-1α serves as a co-linker between AD and T2DM

Alzheimer's disease (AD)-related brain deterioration is linked to the type 2 diabetes mellitus (T2DM) features hyperglycemia, hyperinsulinemia, and insulin resistance. Hypoxia as a common risk factor for both AD and T2DM. Hypoxia-inducible factor-1 alpha (HIF-1α) acts as the main regulator of the hypoxia response and may be a key target in the comorbidity of AD and T2DM. HIF-1α expression is closely related to hyperglycemia, insulin resistance, and inflammation. Tissue oxygen consumption disrupts HIF-1α homeostasis, leading to increased reactive oxygen species levels and the inhibition of insulin receptor pathway activity, causing neuroinflammation, insulin resistance, abnormal Aβ deposition, and tau hyperphosphorylation. HIF-1α activation also leads to the deposition of Aβ by promoting the abnormal shearing of amyloid precursor protein and inhibiting the degradation of Aβ, and it promotes tau hyperphosphorylation by activating oxidative stress and the activation of astrocytes, which further exasperates AD. Therefore, we believe that HIF-α has great potential as a target for the treatment of AD. Importantly, the intracellular homeostasis of HIF-1α is a more crucial factor than its expression level.

Diabetic peripheral neuropathy: pathogenetic mechanisms and treatment

Diabetic peripheral neuropathy (DPN) refers to the development of peripheral nerve dysfunction in patients with diabetes when other causes are excluded. Diabetic distal symmetric polyneuropathy (DSPN) is the most representative form of DPN. As one of the most common complications of diabetes, its prevalence increases with the duration of diabetes. 10-15% of newly diagnosed T2DM patients have DSPN, and the prevalence can exceed 50% in patients with diabetes for more than 10 years. Bilateral limb pain, numbness, and paresthesia are the most common clinical manifestations in patients with DPN, and in severe cases, foot ulcers can occur, even leading to amputation. The etiology and pathogenesis of diabetic neuropathy are not yet completely clarified, but hyperglycemia, disorders of lipid metabolism, and abnormalities in insulin signaling pathways are currently considered to be the initiating factors for a range of pathophysiological changes in DPN. In the presence of abnormal metabolic factors, the normal structure and function of the entire peripheral nervous system are disrupted, including myelinated and unmyelinated nerve axons, perikaryon, neurovascular, and glial cells. In addition, abnormalities in the insulin signaling pathway will inhibit neural axon repair and promote apoptosis of damaged cells. Here, we will discuss recent advances in the study of DPN mechanisms, including oxidative stress pathways, mechanisms of microvascular damage, mechanisms of damage to insulin receptor signaling pathways, and other potential mechanisms associated with neuroinflammation, mitochondrial dysfunction, and cellular oxidative damage. Identifying the contributions from each pathway to neuropathy and the associations between them may help us to further explore more targeted screening and treatment interventions.

Novel drugs affecting diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) poses a significant threat, affecting half of the global diabetic population and leading to severe complications, including pain, impaired mobility, and potential amputation. The delayed manifestation of diabetic neuropathy (DN) makes early diagnosis challenging, contributing to its debilitating impact on individuals with diabetes mellitus (DM). This review examines the multifaceted nature of DPN, focusing on the intricate interplay between oxidative stress, metabolic pathways, and the resulting neuronal damage. It delves into the challenges of diagnosing DN, emphasizing the critical role played by hyperglycemia in triggering these cascading effects. Furthermore, the study explores the limitations of current neuropathic pain drugs, prompting an investigation into a myriad of pharmaceutical agents tested in both human and animal trials over the past decade. The methodology scrutinizes these agents for their potential to provide symptomatic relief for DPN. The investigation reveals promising results from various pharmaceutical agents tested for DPN relief, showcasing their efficacy in ameliorating symptoms. However, a notable gap persists in addressing the underlying problem of DPN. The results underscore the complexity of DPN and the challenges in developing therapies that go beyond symptomatic relief. Despite advancements in treating DPN symptoms, there remains a scarcity of options addressing the underlying problem. This review consolidates the state-of-the-art drugs designed to combat DPN, highlighting their efficacy in alleviating symptoms. Additionally, it emphasizes the need for a deeper understanding of the diverse processes and pathways involved in DPN pathogenesis.

Role of glycolysis in diabetic atherosclerosis

Diabetes mellitus is a kind of typical metabolic disorder characterized by elevated blood sugar levels. Atherosclerosis (AS) is one of the most common complications of diabetes. Modern lifestyles and trends that promote overconsumption and unhealthy practices have contributed to an increase in the annual incidence of diabetic AS worldwide, which has created a heavy burden on society. Several studies have shown the significant effects of glycolysis-related changes on the occurrence and development of diabetic AS, which may serve as novel thera-peutic targets for diabetic AS in the future. Glycolysis is an important metabolic pathway that generates energy in various cells of the blood vessel wall. In particular, it plays a vital role in the physiological and pathological activities of the three important cells, Endothelial cells, macrophages and vascular smooth muscle cells. There are lots of similar mechanisms underlying diabetic and common AS, the former is more complex. In this article, we describe the role and mechanism underlying glycolysis in diabetic AS, as well as the therapeutic targets, such as trained immunity, microRNAs, gut microbiota, and associated drugs, with the aim to provide some new perspectives and potentially feasible programs for the treatment of diabetic AS in the foreseeable future.

Nicotinamide Prevents Diabetic Brain Inflammation via NAD+-Dependent Deacetylation Mechanisms

This study investigated the effect of nicotinamide (NAM) supplementation on the development of brain inflammation and microglial activation in a mouse model of type 1 diabetes mellitus. C57BL/6J male mice, which were made diabetic with five consecutive, low-dose (55 mg/kg i.p.) streptozotocin (STZ) injections. Diabetic mice were randomly distributed in different experimental groups and challenged to different doses of NAM (untreated, NAM low-dose, LD, 0.1%; NAM high-dose, HD, 0.25%) for 25 days. A control, non-diabetic group of mice was used as a reference. The NAD+ content was increased in the brains of NAM-treated mice compared with untreated diabetic mice (NAM LD: 3-fold; NAM HD: 3-fold, p-value < 0.05). Immunohistochemical staining revealed that markers of inflammation (TNFα: NAM LD: -35%; NAM HD: -46%; p-value < 0.05) and microglial activation (IBA-1: NAM LD: -29%; NAM HD: -50%; p-value < 0.05; BDKRB1: NAM LD: -36%; NAM HD: -37%; p-value < 0.05) in brains from NAM-treated diabetic mice were significantly decreased compared with non-treated T1D mice. This finding was accompanied by a concomitant alleviation of nuclear NFκB (p65) signaling in treated diabetic mice (NFκB (p65): NAM LD: -38%; NAM HD: -53%, p-value < 0.05). Notably, the acetylated form of the nuclear NFκB (p65) was significantly decreased in the brains of NAM-treated, diabetic mice (NAM LD: -48%; NAM HD: -63%, p-value < 0.05) and inversely correlated with NAD+ content (r = -0.50, p-value = 0.03), suggesting increased activity of NAD+-dependent deacetylases in the brains of treated mice. Thus, dietary NAM supplementation in diabetic T1D mice prevented brain inflammation via NAD+-dependent deacetylation mechanisms, suggesting an increased action of sirtuin signaling.

Molecular Insights of Plant Phytochemicals Against Diabetic Neuropathy

Diabetes and its associated complications including diabetic neuropathy have become a menacing headache for health workers and scientists all over the world. The number of diabetic individuals has been growing exponentially every day while the entire medical fraternity feels crippled and unable to handle such an enormous and anarchical scenario. The disease also demonstrates itself in the patients in numerous ways ranging from a little discomfort to death. Diabetic neuropathy has a poor prognosis since it might go unnoticed for years after the onset of diabetes. The etiology of the disease has been linked to oxidative stress caused by increased free radical production. Hyperglycemia causes multiple metabolic pathways to be activated, as well as significant oxidative stress, which becomes the major cause of cell death, culminating in Diabetic Neuropathy. So, it is the need of the hour to find out permanent treatment for this life-threatening disease. The primary goal of this study is to emphasize the potential importance of numerous processes and pathways in the development of diabetic neuropathy as well as the possible role of plant metabolites to control the disease at a molecular level. A possible mechanism was also summarized in the study about scavenging the reactive oxygen species by a flavonoid component. The study also covered the in vivo data of various plants and some of the flavonoid compounds actively studied against Diabetic Neuropathy by inhibiting or reducing the contributing factors such as proinflammatory cytokines, ROS, RNS inhibition, and upregulating the various cellular antioxidants such as GSH, SOD, and CAT.

An Insight into Potential Pharmacotherapeutic Agents for Painful Diabetic Neuropathy

Diabetes is the 4th most common disease affecting the world's population. It is accompanied by many complications that deteriorate the quality of life. Painful diabetic neuropathy (PDN) is one of the debilitating consequences of diabetes that effects one-third of diabetic patients. Unfortunately, there is no internationally recommended drug that directly hinders the pathological mechanisms that result in painful diabetic neuropathy. Clinical studies have shown that anticonvulsant and antidepressant therapies have proven fruitful in management of pain associated with PDN. Currently, the FDA approved medications for painful diabetic neuropathies include duloxetine, pregabalin, tapentadol extended release, and capsaicin (for foot PDN only). The FDA has also approved the use of spinal cord stimulation system for the treatment of diabetic neuropathy pain. The drugs recommended by other regulatory bodies include gabapentin, amitriptyline, dextromethorphan, tramadol, venlafaxine, sodium valproate, and 5 % lidocaine patch. These drugs are only partially effective and have adverse effects associated with their use. Treating painful symptoms in diabetic patient can be frustrating not only for the patients but also for health care workers, so additional clinical trials for novel and conventional treatments are required to devise more effective treatment for PDN with minimal side effects. This review gives an insight on the pathways involved in the pathogenesis of PDN and the potential pharmacotherapeutic agents. This will be followed by an overview on the FDA-approved drugs for PDN and commercially available topical analgesic and their effects on painful diabetic neuropathies.

Glyceraldehyde-3-phosphate dehydrogenase and glutamine synthetase inhibition in the presence of pro-inflammatory cytokines contribute to the metabolic imbalance of diabetic retinopathy

Diabetic retinopathy (DR) is the leading cause of vision impairment in working age adults. In addition to hyperglycemia, retinal inflammation is an important driving factor for DR development. Although DR is clinically described as diabetes-induced damage to the retinal blood vessels, several studies have reported that metabolic dysregulation occurs in the retina prior to the development of microvascular damage. The two most commonly affected metabolic pathways in diabetic conditions are glycolysis and the glutamate pathway. We investigated the role of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and glutamine synthetase (GS) in an in-vitro model of DR incorporating high glucose and pro-inflammatory cytokines. We found that GAPDH and GS enzyme activity were not significantly affected in hyperglycemic conditions or after exposure to cytokines alone, but were significantly decreased in the DR model. This confirmed that pro-inflammatory cytokines IL-1β and TNFα enhance the hyperglycemic metabolic deficit. We further investigated metabolite and amino acid levels after specific pharmacological inhibition of GAPDH or GS in the absence/presence of pro-inflammatory cytokines. The results indicate that GAPDH inhibition increased glucose and addition of cytokines increased lactate and ATP levels and reduced glutamate levels. GS inhibition did not alter retinal metabolite levels but the addition of cytokines increased ATP levels and caused glutamate accumulation in Müller cells. We conclude that it is the action of pro-inflammatory cytokines concomitantly with the inhibition of the glycolytic or GS mediated glutamate recycling that contribute to metabolic dysregulation in DR. Therefore, in the absence of good glycemic control, therapeutic interventions aimed at regulating inflammation may prevent the onset of early metabolic imbalance in DR.

PARP-1-Associated Pathological Processes: Inhibition by Natural Polyphenols

Poly (ADP-ribose) polymerase-1 (PARP-1) is a nuclear enzyme involved in processes of cell cycle regulation, DNA repair, transcription, and replication. Hyperactivity of PARP-1 induced by changes in cell homeostasis promotes development of chronic pathological processes leading to cell death during various metabolic disorders, cardiovascular and neurodegenerative diseases. In contrast, tumor growth is accompanied by a moderate activation of PARP-1 that supports survival of tumor cells due to enhancement of DNA lesion repair and resistance to therapy by DNA damaging agents. That is why PARP inhibitors (PARPi) are promising agents for the therapy of tumor and metabolic diseases. A PARPi family is rapidly growing partly due to natural polyphenols discovered among plant secondary metabolites. This review describes mechanisms of PARP-1 participation in the development of various pathologies, analyzes multiple PARP-dependent pathways of cell degeneration and death, and discusses representative plant polyphenols, which can inhibit PARP-1 directly or suppress unwanted PARP-dependent cellular processes.

Subproteomic profiling from renal cortices in OLETF rats reveals mutations of multiple novel genes in diabetic nephropathy

BACKGROUND

Diabetic nephropathy (DN) is a serious threat to human health, but its pathogenesis is not fully understood. Otsuka Long-Evans Tokushima Fatty (OLETF) rats are very similar to human DN in many aspects such as pathological changes and processes, and are deemed to be an ideal rodent model.

OBJECTIVE

This study was aimed to explore the pathogenesis of DN by analyzing the protein expression profile from renal cortices in OLETF rats.

METHODS

Thirty-six-week-old diabetic OLETF rats and normal control Long-Evans Tokushima Otsuka (LETO) rats were nephrectomized, and the renal cortices were isolated. The proteins were separated by soluble and insoluble high-resolution subproteomics methods for the analysis and identification of differential proteins.

RESULTS

Thirty-six differentially expressed proteins were found. Among them, 11 proteins had different isoelectric points and molecular weights between OLETF and LETO rats. Further sequencing identified point mutations in genes encoding eight of these proteins, which are involved in many biological processes closely related to DN, including oxidative stress and inflammation. Five of these eight proteins have not been reported in DN.

CONCLUSION

This study reveals mutations of multiple novel genes in diabetic OLETF rats, providing some new potential targets for the pathogenesis of DN and helping to better understand the pathogenesis of DN.

Role of pyruvate in maintaining cell viability and energy production under high-glucose conditions

Pyruvate functions as a key molecule in energy production and as an antioxidant. The efficacy of pyruvate supplementation in diabetic retinopathy and nephropathy has been shown in animal models; however, its significance in the functional maintenance of neurons and Schwann cells under diabetic conditions remains unknown. We observed rapid and extensive cell death under high-glucose (> 10 mM) and pyruvate-starved conditions. Exposure of Schwann cells to these conditions led to a significant decrease in glycolytic flux, mitochondrial respiration and ATP production, accompanied by enhanced collateral glycolysis pathways (e.g., polyol pathway). Cell death could be prevented by supplementation with 2-oxoglutarate (a TCA cycle intermediate), benfotiamine (the vitamin B1 derivative that suppresses the collateral pathways), or the poly (ADP-ribose) polymerase (PARP) inhibitor, rucaparib. Our findings suggest that exogenous pyruvate plays a pivotal role in maintaining glycolysis–TCA cycle flux and ATP production under high-glucose conditions by suppressing PARP activity.

PARP1 deficiency protects against hyperglycemia-induced neointimal hyperplasia by upregulating TFPI2 activity in diabetic mice

Diabetes mellitus (DM) promotes neointimal hyperplasia, characterized by dysregulated proliferation and accumulation of vascular smooth muscle cells (VSMCs), leading to occlusive disorders, such as atherosclerosis and stenosis. Poly (ADP-ribose) polymerase 1 (PARP1), reported as a crucial mediator in tumor proliferation and transformation, has a pivotal role in DM. Nonetheless, the function and potential mechanism of PARP1 in diabetic neointimal hyperplasia remain unclear. In this study, we constructed PARP1 conventional knockout (PARP1^−/−) mice, and ligation of the left common carotid artery was performed to induce neointimal hyperplasia in Type I diabetes mellitus (T1DM) mouse models. PARP1 expression in the aorta arteries of T1DM mice increased significantly and genetic deletion of PARP1 showed an inhibitory effect on the neointimal hyperplasia. Furthermore, our results revealed that PARP1 enhanced diabetic neointimal hyperplasia via downregulating tissue factor pathway inhibitor (TFPI2), a suppressor of vascular smooth muscle cell proliferation and migration, in which PARP1 acts as a negative transcription factor augmenting TFPI2 promoter DNA methylation. In conclusion, these results suggested that PARP1 accelerates the process of hyperglycemia-induced neointimal hyperplasia via promoting VSMCs proliferation and migration in a TFPI2 dependent manner.

Nutrigenomics in Regulating the Expression of Genes Related to Type 2 Diabetes Mellitus

Nutrigenomics is the study of the gene-nutrient interaction and it indicates that some nutrients, called bioactive compounds, can mold the genetic expression or change the nucleotide chain. Polyphenols are secondary metabolites found in plants that are regularly consumed in functional foods and help prevent or delay the onset of type 2 diabetes mellitus (T2DM) and its complications. This article objected to review studies about the interaction of diet with polyphenols and Mediterranean diet in the expression of human genes related to T2DM. Resveratrol acts as an antioxidant, anti-inflammatory, and increases mitochondrial function. Regular consumption of quercetin resulted in improvement of hypertension and suppression of diabetes-induced vasoconstriction. Genistein also showed positive results in T2DM, such as increased cell mass and improved glucose tolerance and insulin levels. Catechins showed efficiency in inducing genes in triacylglycerol biosynthesis, inhibition of fatty acids and cholesterol, and resulting in their participation in mitigating complications of diabetes. Lastly, curcumin was demonstrated to be a protector of the pancreatic islets against streptozotocin-induced oxidative stress. Growing evidence suggest that bioactive compounds such as polyphenols have an important role in T2DM and the prevention and treatment of its complication, as they cause activation or inhibition of related genes.

Nampt Potentiates Antioxidant Defense in Diabetic Cardiomyopathy

[Figure: see text].

Inflammation and apoptosis, two key events induced by hyperglycemia mediated reactive nitrogen species in RGC-5 cells

Nitrosative stress plays a critical role in retinal injury in high glucose (HG) environment of eye, but the mechanisms remain poorly understood. Here we tested the hypothesis that HG induced reactive nitrogen species (RNS) production acts as a key functional mediator of antioxidant depletion, mitochondrial dysfunction, biomolecule damage, inflammation and apoptosis. Our findings illustrated that exposure of cultured RGC-5 cells to HG significantly disrupts the antioxidant defense mechanism and mitochondrial machineries by increasing the loss of mitochondrial membrane potential (ΔѰM) and elevating mitochondrial mass. Furthermore, we used biochemical tools to analyze the changes in metabolites, sulfur amino acids (SAAs) such as L-glutathione (GSH) and L-cysteine (Cys), in the presence of HG environment. These metabolic changes were followed by an increase in glycolytic flux that is phosphofructokinase-2 (PFK-2) activity. Moreover, HG exposure results in a significant disruption of protein carbonylation (PC) and lipid peroxidation (LPO), downregulation of OGG1 and increase in 8-OHdG accumulations in RGC-5 cells. In addition, our results demonstrated that HG environment coinciding with increased expression of inflammatory mediators, cell cycle deregulation, decreased in cell viability and expression of FoxOs, increased lysosomal content leading to apoptosis. Pre-treatment of selective inhibitors of RNS significantly reduced the HG-induced cell cycle deregulation and apoptosis in RGC-5 cells. Collectively, these results illustrated that accumulated RNS exacerbates the antioxidant depletion, mitochondrial dysfunction, biomolecule damage, inflammation and apoptosis induced by HG exposure in RGC-5 cells. Treatment of pharmacological inhibitors attenuated the HG induced in retinal cells.

Melatonin prevents blood-retinal barrier breakdown and mitochondrial dysfunction in high glucose and hypoxia-induced in vitro diabetic macular edema model

Diabetic macular edema (DME) is a leading cause of blindness in diabetic retinopathy. Prolonged hyperglycemia plus hypoxia contributes to DME pathogenesis. Retinal pigmented epithelial cells comprise the outer blood-retinal barrier and are essential for maintaining physiological functioning of the retina. Melatonin acts as an antioxidant and regulator of mitochondrial bioenergetics and has a protective effect against ocular diseases. However, the role of mitochondrial dysfunction and the therapeutic potential of melatonin in DME remain largely unexplored. Here, we used an in vitro model of DME to investigate blood-retinal barrier integrity and permeability, angiogenesis, mitochondrial dynamics, and apoptosis signaling to evaluate the potential protective efficacy of melatonin in DME. We found that melatonin prevents cell hyper-permeability and outer barrier breakdown by reducing HIF-1α, HIF-1β and VEGF and VEGF receptor gene expression. In addition, melatonin reduced the expression of genes involved in mitochondrial fission (DRP1, hFis1, MIEF2, MFF), mitophagy (PINK, BNip3, NIX), and increased the expression of genes involved in mitochondrial biogenesis (PGC-1α, NRF2, PPAR-γ) to maintain mitochondrial homeostasis. Moreover, melatonin prevented apoptosis of retinal pigmented epithelial cells. Our results suggest that mitochondrial dysfunction may be involved in DME pathology, and melatonin may have therapeutic value in DME, by targeting signaling in mitochondria.

Propolis ethanol extract abrogates hyperglycemia, lipotoxicity, and lowered hepatic poly (ADP-ribose) polymerase protein level in male albino rats

Background and aim

Diabetes is a major cause of death worldwide and currently available allopathic drugs presents adverse side effects, thus, necessitating a continuous screening for natural products. This study therefore investigated the effects of Propolis Ethanol Extract (PEE) on blood sugar, lipid metabolism, and poly-(ADP)-ribose polymerase (PARPs) protein level of diabetic male Wistar rats.

Methodology

Seventy rats weighing between (150-180) g used in this study were randomized into seven (7) groups as follows: group 1 (Normal control given Olive oil), group 2 (Diabetic control given Olive oil), group 3 [Diabetic + PEE (200 mg/kg)], group 4 [Diabetic + (PEE 600 mg/kg)], group 5 [Diabetic + Glibenclamide (10 mg/kg)], group 6 [Normal + PEE (200 mg/kg)], and group 7 [Normal + PEE (600 mg/kg)]. Diabetes was induced by a single intraperitoneal injection of streptozotocin (65 mg/kg in 0.1 M citrate buffer pH 4.5), while the vehicle and PEE were orally administered once daily. Treatment with PEE commenced after the confirmation of diabetes. Five rats from each group were sacrificed after the third and sixth weeks of PEE treatment.

Results

Administration of PEE significantly (P < 0.05) lowered the elevated fasting blood sugar, improves body weight, and abated lipotoxicity in the brain, heart, liver and kidney of the treated groups in a dose- and duration-dependent manners. The increased protein level of PARPs and lowered hydroxyl methyl-glutaryl CoA reductase activity were significantly reversed after PEE treatment.

Conclusions

This study concludes that PEE might be a suitable and viable regimen against diabetic complications in rats.

Graphical abstract

The Long Non-Coding RNA HOTAIR Is a Critical Epigenetic Mediator of Angiogenesis in Diabetic Retinopathy

Purpose

Diabetic retinopathy (DR) remains a pressing issue worldwide. Abnormal angiogenesis is a distinct vascular lesion in DR, and research has established that vascular endothelial growth factor A (VEGF-A) is a primary mediator of such changes. However, limitations in current anti-VEGF therapies suggest that our understanding of molecular networks underlying ocular angiogenesis remains far from complete. Based on our long non-coding RNA (lncRNA) array analyses, HOX antisense intergenic RNA (HOTAIR) was identified as one of the top upregulated lncRNAs in high glucose-cultured human retinal endothelial cells (HRECs). Given the well-documented roles of HOTAIR in cancer, no studies have examined the epigenetic implications of HOTAIR in DR, and we investigated such relationships herein.

Methods

We used HRECs exposed to various glucose concentrations and epigenetic modulators to examine HOTAIR, angiogenic, and DR-related molecular markers. Oxidative stress, angiogenesis, and mitochondrial dysfunction were assessed. Retinal tissues of diabetic rodents and the vitreous humor and serum of patients with proliferative DR were also investigated.

Results

Hyperglycemia significantly augmented HOTAIR expression in HRECs and promoted angiogenesis, oxidative damage, and mitochondrial aberrations. Similarly, vitreous humor and serum from proliferative DR patients and retinas from diabetic animals demonstrated increased HOTAIR expression compared to non-diabetic controls. HOTAIR knockdown protected against glucose-induced increases of angiogenic and diabetes-associated molecules in the retina. Mechanistically, we showed that HOTAIR exerts its capabilities by preventing oxidative stress and modulating epigenetic pathways involving histone methylation, histone acetylation, DNA methylation, and transcription factors.

Conclusions

Our findings suggest that HOTAIR is a critical lncRNA in the pathogenesis of DR and may potentially be important for diagnostic and therapeutic targeting.

Mechanistic dissection of diabetic retinopathy using the protein-metabolite interactome

Purpose

The current study aims to determine the molecular mechanisms of diabetic retinopathy (DR) using the protein-protein interactome and metabolome map. We examined the protein network of novel biomarkers of DR for direct (physical) and indirect (functional) interactions using clinical target proteins in different models.

Methods

We used proteomic tools including 2-dimensional gel electrophoresis, mass spectrometry analysis, and database search for biomarker identification using in vivo murine and human model of diabetic retinopathy and in vitro model of oxidative stress. For the protein interactome and metabolome mapping, various bioinformatic tools that include STRING and OmicsNet were used.

Results

We uncovered new diabetic biomarkers including prohibitin (PHB), dynamin 1, microtubule-actin crosslinking factor 1, Toll-like receptor (TLR 7), complement activation, as well as hypothetical proteins that include a disintegrin and metalloproteinase (ADAM18), vimentin III, and calcium-binding C2 domain-containing phospholipid-binding switch (CAC2PBS) using a proteomic approach. Proteome networks of protein interactions with diabetic biomarkers were established using known DR-related proteome data. DR metabolites were interconnected to establish the metabolome map. Our results showed that mitochondrial protein interactions were changed during hyperglycemic conditions in the streptozotocin-treated murine model and diabetic human tissue.

Conclusions

Our interactome mapping suggests that mitochondrial dysfunction could be tightly linked to various phases of DR pathogenesis including altered visual cycle, cytoskeletal remodeling, altered lipid concentration, inflammation, PHB depletion, tubulin phosphorylation, and altered energy metabolism. The protein-metabolite interactions in the current network demonstrate the etiology of retinal degeneration and suggest the potential therapeutic approach to treat DR.

Nonhormonal Treatment for Endometriosis Focusing on Redox Imbalance

The aim of this review is to investigate the oxidant/antioxidant status and its regulatory mechanisms in patients with endometriosis and to summarize the antioxidant therapy as an alternative to hormonal therapy for endometriosis. Each keyword alone or in combination was used to search from PubMed and Embase by applying the filters of the title and the publication years between January 2000 and March 2020. Endometriosis is a chronic inflammatory disease characterized by repeated episodes of hemorrhage. Methemoglobin in repeated hemorrhage produces large amounts of superoxide anion via the autoxidation of hemoglobin. Excessive free-radical production causes redox imbalance, leading to inadequate antioxidant defenses and damage to endometrial cells, but may contribute to endometrial cell growth and survival through activation of various signaling pathways. In addition, to overcome excessive oxidative stress, estradiol participates in the induction of antioxidants such as superoxide dismutase in mitochondria. Several antioxidants that suppress free radicals may be effective in endometriosis-related pain. We searched for 23 compounds and natural substances that could reduce the pain caused by superoxide/reactive oxygen species in basic research and animal models. Next, we built a list of 16 drugs that were suggested to be effective against endometriosis other than hormone therapy in preclinical studies and clinical trials. Of the 23 and 16 drugs, 4 overlapping drugs could be potential candidates for clinically reducing endometriosis-related pain caused by superoxide anion/reactive oxygen species. These drugs include polyphenols (resveratrol and polydatin), dopamine agonists (cabergoline), and statins (simvastatin). However, no randomized controlled trials have evaluated the efficacy of these drugs. In conclusion, this review summarizes the following 2 points: superoxide anion generation by methemoglobin is enhanced in endometriosis, resulting in redox imbalance; and some compounds and natural substances that can suppress free radicals may be effective in endometriosis-related pain. Further randomized clinical trials based on larger series are mandatory to confirm the promising role of antioxidants in the nonhormonal management of endometriosis.

Pathophysiology, Clinical Characteristics of Diabetic Cardiomyopathy: Therapeutic Potential of Natural Polyphenols

Diabetic cardiomyopathy (DCM) is an outcome of disturbances in metabolic activities through oxidative stress, local inflammation, and fibrosis, as well as a prime cause of fatality worldwide. Cardiovascular disorders in diabetic individuals have become a challenge in diagnosis and formulation of treatment prototype. It is necessary to have a better understanding of cellular pathophysiology that reveal the therapeutic targets and prevent the progression of cardiovascular diseases due to hyperglycemia. Critical changes in levels of collagen and integrin have been observed in the extracellular matrix of heart, which was responsible for cardiac remodeling in diabetic patients. This review explored the understanding of the mechanisms of how the phytochemicals provide cardioprotection under diabetes along with the caveats and provide future perspectives on these agents as prototypes for the development of drugs for managing DCM. Thus, here we summarized the effect of various plant extracts and natural polyphenols tested in preclinical and cell culture models of diabetic cardiomyopathy. Further, the potential use of selected polyphenols that improved the therapeutic efficacy against diabetic cardiomyopathy is also illustrated.

Selective Targeting of Cancerous Mitochondria and Suppression of Tumor Growth Using Redox-Active Treatment Adjuvant

Redox-active substances and their combinations, such as of quinone/ascorbate and in particular menadione/ascorbate (M/A; also named Apatone®), attract attention with their unusual ability to kill cancer cells without affecting the viability of normal cells as well as with the synergistic anticancer effect of both molecules. So far, the primary mechanism of M/A-mediated anticancer effects has not been linked to the mitochondria. The aim of our study was to clarify whether this “combination drug” affects mitochondrial functionality specifically in cancer cells. Studies were conducted on cancer cells (Jurkat, Colon26, and MCF7) and normal cells (normal lymphocytes, FHC, and MCF10A), treated with different concentrations of menadione, ascorbate, and/or their combination (2/200, 3/300, 5/500, 10/1000, and 20/2000 μM/μM of M/A). M/A exhibited highly specific and synergistic suppression on cancer cell growth but without adversely affecting the viability of normal cells at pharmacologically attainable concentrations. In M/A-treated cancer cells, the cytostatic/cytotoxic effect is accompanied by (i) extremely high production of mitochondrial superoxide (up to 15-fold over the control level), (ii) a significant decrease of mitochondrial membrane potential, (iii) a decrease of the steady-state levels of ATP, succinate, NADH, and NAD⁺, and (iv) a decreased expression of programed cell death ligand 1 (PD-L1)—one of the major immune checkpoints. These effects were dose dependent. The inhibition of NQO1 by dicoumarol increased mitochondrial superoxide and sensitized cancer cells to M/A. In normal cells, M/A induced relatively low and dose-independent increase of mitochondrial superoxide and mild oxidative stress, which seems to be well tolerated. These data suggest that all anticancer effects of M/A result from a specific mechanism, tightly connected to the mitochondria of cancer cells. At low/tolerable doses of M/A (1/100-3/300 μM/μM) attainable in cancer by oral and parenteral administration, M/A sensitized cancer cells to conventional anticancer drugs, exhibiting synergistic or additive cytotoxicity accompanied by impressive induction of apoptosis. Combinations of M/A with 13 anticancer drugs were investigated (ABT-737, barasertib, bleomycin, BEZ-235, bortezomib, cisplatin, everolimus, lomustine, lonafarnib, MG-132, MLN-2238, palbociclib, and PI-103). Low/tolerable doses of M/A did not induce irreversible cytotoxicity in cancer cells but did cause irreversible metabolic changes, including: (i) a decrease of succinate and NADH, (ii) depolarization of the mitochondrial membrane, and (iii) overproduction of superoxide in the mitochondria of cancer cells only. In addition, M/A suppressed tumor growth in vivo after oral administration in mice with melanoma and the drug downregulated PD-L1 in melanoma cells. Experimental data suggest a great potential for beneficial anticancer effects of M/A through increasing the sensitivity of cancer cells to conventional anticancer therapy, as well as to the immune system, while sparing normal cells. We hypothesize that M/A-mediated anticancer effects are triggered by redox cycling of both substances, specifically within dysfunctional mitochondria. M/A may also have a beneficial effect on the immune system, making cancer cells “visible” and more vulnerable to the native immune response.

Nitroxyl: A Novel Strategy to Circumvent Diabetes Associated Impairments in Nitric Oxide Signaling

Diabetes is associated with an increased mortality risk due to cardiovascular complications. Hyperglycemia-induced oxidative stress underlies these complications, leading to an impairment in endogenous nitric oxide (NO•) generation, together with reductions in NO• bioavailability and NO• responsiveness in the vasculature, platelets and myocardium. The latter impairment of responsiveness to NO•, termed NO• resistance, compromises the ability of traditional NO•-based therapeutics to improve hemodynamic status during diabetes-associated cardiovascular emergencies, such as acute myocardial infarction. Whilst a number of agents can ameliorate (e.g. angiotensin converting enzyme [ACE] inhibitors, perhexiline, statins and insulin) or circumvent (e.g. nitrite and sGC activators) NO• resistance, nitroxyl (HNO) donors offer a novel opportunity to circumvent NO• resistance in diabetes. With a suite of vasoprotective properties and an ability to enhance cardiac inotropic and lusitropic responses, coupled with preserved efficacy in the setting of oxidative stress, HNO donors have intact therapeutic potential in the face of diminished NO• signaling. This review explores the major mechanisms by which hyperglycemia-induced oxidative stress drives NO• resistance, and the therapeutic potential of HNO donors to circumvent this to treat cardiovascular complications in type 2 diabetes mellitus.

Methylglyoxal and soluble RAGE in type 2 diabetes mellitus: Association with oxidative stress

Purpose

Methylglyoxal (MGO) and MGO related advance end product (AGE) are thought to contribute to the development of diabetes and its complications. The present study was intended to determine plasma MGO and sRAGE levels in T2DM patients and to assess the relationship between MGO and other parameters, such as sRAGE and oxidative markers.

Methods

The study was carried out in 100 control and T2DM subjects. Methylglyoxal, sRAGE, HbA1c, and other markers were measured by using a standard protocol and the relationship between variables was analyzed using Spearman's correlation analysis.

Results

Plasma MGO levels in patients with T2DM (221.1 ± 9.50 ng/mL) were significantly higher than in control subjects (121.1 ± 6.52 ng/mL, P < 0.001). The plasma level of MGO was positively correlated with glycosylated hemoglobin (HbA1c, r = 0.50, P < 0.001). Plasma soluble form of RAGE (sRAGE) was significantly decreased in T2DM subjects (5.3 ± 0.64 ng/mL) as compared to the control group (7.7 ± 0.86 ng/mL, p < 0.05). However, at increased level of glycation (HbA1c > 10%), the sRAGE level was 6.2 ± 0.42 ng/mL and was not statistically significant as compared to control healthy group (> 0.05). Moreover, we have not found any correlation between MGO and other markers (p > 0.05).

Conclusions

The findings of the present study showed that increased plasma MGO level is significantly associated with the HbA1c levels in T2DM patients. Moreover, the study shows that plasma sRAGE level is significantly augmented at increased level of glycation (HbA1c > 10%) in T2DM patients.

Abdominal aortic aneurysm: a review on the role of oral antidiabetic drugs

INTRODUCTION

A paradoxical negative association between diabetes mellitus and abdominal aortic aneurysm (AAA) prevalence and growth is established. However, so far is not possible to determine whether this protection comes from the disease itself or the medication for Diabetes. The aim of this manuscript is to review the association between oral antidiabetic drugs and AAA incidence and growth.

EVIDENCE ACQUISITION

A search was conducted on PubMed and Scopus databases until December 2019 to identify publications reporting on the association between oral antidiabetic drugs (biguanides/metformin, sulfonylureas(SU), thiazolidinediones(TZD), dipeptidyl-peptidase 4(DPP-4) inhibitors, glucagon-like peptide 1(GLP-1) agonists, sodium-glucose transporter protein-2(SGLT2) inhibitors) and the outcomes AAA incidence and growth. Only data from human studies were considered, with a minimum of 3 months follow-up.

EVIDENCE SYNTHESIS

Six studies enrolling 25,810 patients were included: one reporting on the AAA risk and five reporting on AAA growth. Metformin prescription was associated with a 28% reduction in AAA occurrence, while SU and TZD were associated with a 18% decrease in AAA risk. Regarding AAA enlargement, results were concordant for a slower expansion rate associated with metformin, with a decrease ranging from -0.30 mm/y to -1.30 mm/y, but not consistent for other antidiabetic drugs.

CONCLUSIONS

Metformin seems to be associated with a decrease in AAA risk and enlargement rate. Evidence for the other classes is lacking. Studies evaluating the association between oral antidiabetic drugs and AAA progression, independently of the diabetic status, are needed.

The role of ADP-ribose metabolism in metabolic regulation, adipose tissue differentiation, and metabolism

In this review, Szanto et al. summarize the metabolic regulatory roles of PARP enzymes and their associated pathologies.

Poly(ADP-ribose) polymerases (PARPs or ARTDs), originally described as DNA repair factors, have metabolic regulatory roles. PARP1, PARP2, PARP7, PARP10, and PARP14 regulate central and peripheral carbohydrate and lipid metabolism and often channel pathological disruptive metabolic signals. PARP1 and PARP2 are crucial for adipocyte differentiation, including the commitment toward white, brown, or beige adipose tissue lineages, as well as the regulation of lipid accumulation. Through regulating adipocyte function and organismal energy balance, PARPs play a role in obesity and the consequences of obesity. These findings can be translated into humans, as evidenced by studies on identical twins and SNPs affecting PARP activity.

Potential Biomarkers in Diabetic Retinopathy

BACKGROUND

Diabetic retinopathy is one of the important complications of diabetes. In major cases, diabetic retinopathy is unnoticed until the irreversible damage to eye occurs and leads to blurred vision and, eventually, blindness.

OBJECTIVE

The pathogenesis and diagnosis of diabetic retinopathy are very complex and not fully understood. Currently, well-established laser techniques and medications are available, but these treatment options have their own shortcomings on biological systems. Biomarkers can help to overcome this problem due to easy, fast and economical options for diagnosis of diabetic retinopathy.

METHODS

The search terms used were "Diabetic retinopathy", "Biomarkers in diabetic retinopathy", "Novel biomarkers in diabetic retinopathy" and "Potential biomarkers of diabetic retinopathy" by using different scientific resources and databases like EBSCO, ProQuest, PubMed and Scopus. Eligibility criteria included biomarkers involved in diabetic retinopathy in the detectable range. Exclusion criteria included the repetition and duplication of the biomarker in diabetic retinopathy.

RESULTS

Current review and literature study revealed that biomarkers of diabetic retinopathy can be categorized as inflammatory: tumor necrosis factor-α, monocyte chemoattractant protein-1, transforming growth factor- β; antioxidant: nicotinamide adenine dinucleotide phosphate oxidase; nucleic acid: poly ADP ribose polymerase- α, Apelin, Oncofetal; enzyme: ceruloplasmin, protein kinase C; and miscellaneous: erythropoietin. These biomarkers have a great potential in the progression of diabetic retinopathy hence can be used in the diagnosis and management of this debilitating disease.

CONCLUSION

Above mentioned biomarkers play a key role in the pathogenesis of diabetic retinopathy; hence they can also be considered as potential targets for new drug development.

Role of pseudohypoxia in the pathogenesis of type 2 diabetes

Type 2 diabetes is caused by persistent high blood glucose, which is known as diabetic hyperglycemia. This hyperglycemic situation, when not controlled, can overproduce NADH and lower nicotinamide adenine dinucleotide (NAD), thereby creating NADH/NAD redox imbalance and leading to cellular pseudohypoxia. In this review, we discussed two major enzymatic systems that are activated by diabetic hyperglycemia and are involved in creation of this pseudohypoxic condition. One system is aldose reductase in the polyol pathway, and the other is poly (ADP ribose) polymerase. While aldose reductase drives overproduction of NADH, PARP could in contrast deplete NAD. Therefore, activation of the two pathways underlies the major mechanisms of NADH/NAD redox imbalance and diabetic pseudohypoxia. Consequently, reductive stress occurs, followed by oxidative stress and eventual cell death and tissue dysfunction. Additionally, fructose formed in the polyol pathway can also cause metabolic syndrome such as hypertension and nonalcoholic fatty liver disease. Moreover, pseudohypoxia can also lower sirtuin protein contents and induce protein acetylation which can impair protein function. Finally, we discussed the possibility of using nicotinamide riboside, an NAD precursor, as a promising therapeutic agent for restoring NADH/NAD redox balance and for preventing the occurrence of diabetic pseudohypoxia.

ADP-ribosylation signalling and human disease

ADP-ribosylation (ADPr) is a reversible post-translational modification of proteins, which controls major cellular and biological processes, including DNA damage repair, cell proliferation and differentiation, metabolism, stress and immune responses. In order to maintain the cellular homeostasis, diverse ADP-ribosyl transferases and hydrolases are involved in the fine-tuning of ADPr systems. The control of ADPr network is vital, and dysregulation of enzymes involved in the regulation of ADPr signalling has been linked to a number of inherited and acquired human diseases, such as several neurological disorders and in cancer. Conversely, the therapeutic manipulation of ADPr has been shown to ameliorate several disorders in both human and animal models. These include cardiovascular, inflammatory, autoimmune and neurological disorders. Herein, we summarize the recent findings in the field of ADPr, which support the impact of this modification in human pathophysiology and highlight the curative potential of targeting ADPr for translational and molecular medicine.

Identification and quantification of DNA repair protein poly(ADP ribose) polymerase 1 (PARP1) in human tissues and cultured cells by liquid chromatography/isotope-dilution tandem mass spectrometry

Poly(ADP ribose) polymerase 1 (PARP1) is a multifunctional DNA repair protein of the base excision repair pathway and plays a major role in the repair of DNA strand breaks and in replication and transcriptional regulation among other functions. Mounting evidence points to the predictive and prognostic value of PARP1 expression in human cancers. Thus, PARP1 has become an important target in cancer therapy, leading to the development of inhibitors as anticancer drugs. In the past, PARP1 expression levels in tissue samples have generally been estimated by indirect and semi-quantitative immunohistochemical methods. Accurate measurement of PARP1 in normal tissues and malignant tumors of patients will be essential for evaluating PARP1 as a predictive and prognostic biomarker in cancer and other diseases, and for the development and use of its inhibitors in cancer therapy. In this work, we present an approach involving liquid chromatography-isotope-dilution tandem mass spectrometry to positively identify and accurately quantify PARP1 in human tissues and cultured cells. We identified and quantified PARP1 in human normal ovarian tissues and malignant ovarian tumors, and in three pairs of human cell lines, each pair consisting of a normal cell line and its cancerous counterpart. Significantly greater expression of PARP1 was observed in malignant ovarian tissues than in normal ovarian tissues. In the case of one pair of cell lines, the cancerous cell line also exhibited greater expression of PARP1 than in normal cell line. We also show the simultaneous measurement of PARP1 and apurinic/apyrimidinic endonuclease 1 (APE1) in a given protein extract. The approach presented in this work is expected to contribute to the accurate quantitative assessment of PARP1 levels in basic research and clinical studies.

Emerging Biomarkers, Tools, and Treatments for Diabetic Polyneuropathy

Diabetic neuropathy, with its major clinical sequels, notably neuropathic pain, foot ulcers, and autonomic dysfunction, is associated with substantial morbidity, increased risk of mortality, and reduced quality of life. Despite its major clinical impact, diabetic neuropathy remains underdiagnosed and undertreated. Moreover, the evidence supporting a benefit for causal treatment is weak at least in patients with type 2 diabetes, and current pharmacotherapy is largely limited to symptomatic treatment options. Thus, a better understanding of the underlying pathophysiology is mandatory for translation into new diagnostic and treatment approaches. Improved knowledge about pathogenic pathways implicated in the development of diabetic neuropathy could lead to novel diagnostic techniques that have the potential of improving the early detection of neuropathy in diabetes and prediabetes to eventually embark on new treatment strategies. In this review, we first provide an overview on the current clinical aspects and illustrate the pathogenetic concepts of (pre)diabetic neuropathy. We then describe the biomarkers emerging from these concepts and novel diagnostic tools and appraise their utility in the early detection and prediction of predominantly distal sensorimotor polyneuropathy. Finally, we discuss the evidence for and limitations of the current and novel therapy options with particular emphasis on lifestyle modification and pathogenesis-derived treatment approaches. Altogether, recent years have brought forth a multitude of emerging biomarkers reflecting different pathogenic pathways such as oxidative stress and inflammation and diagnostic tools for an early detection and prediction of (pre)diabetic neuropathy. Ultimately, these insights should culminate in improving our therapeutic armamentarium against this common and debilitating or even life-threatening condition.

Potential role of poly (ADP-ribose) polymerase in delayed cerebral vasospasm following subarachnoid hemorrhage in rats

Poly (ADP-ribose) polymerase (PARP) serves a key role in several neurological disorders, however, the specific role of PARP in delayed cerebral vasospasm (DCVS) following subarachnoid hemorrhage (SAH) remains unclear. The present study was conducted to clarify the possible mechanism of PARP in DCVS with the treatment of 3-aminobenzamide (3-AB), a PARP inhibitor. In the preliminary experiment, an internal carotid artery puncture SAH model, a cisterna magna double injection SAH model and prechiasmatic cistern single injection SAH model were compared with respect to mortality and neurobehavioral test results. The prechiasmatic cistern single injection SAH model was chosen to induce DCVS in the formal experiment. In the formal experiment, a total of 96 Sprague Dawley rats were randomly allocated into the sham group, the SAH group and the SAH+3-AB group and then each group was further subdivided into days 3, 5, 7 and 14 post-SAH subgroups (n=8 for each subgroup). The prechiasmatic cistern single injection SAH model was established to induce DCVS. Neurobehavioral testing and HE staining were conducted to evaluate the degree of cerebral vasospasm. PARP activity was assessed by ELISA and immunohistochemistry. An electrophoretic mobility shift assay was used to detect nuclear factor (NF)-κB DNA-binding activity. The expression of monocyte chemotactic protein 1 (MCP-1) and C-reactive protein (CRP) were measured by western blotting. Cerebral vasospasm occurred following SAH and became most severe on around day 7 post-SAH. NF-κB activity, PARP activity, the expression of MCP-1 and CRP exhibited a similar time course to cerebral vasospasm. Treatment with 3-AB alleviated the degree of cerebral vasospasm. NF-κB activity, PARP activity and the expression of MCP-1 and CRP were also suppressed by 3-AB treatment. In conclusion, PARP may serve an important role in regulating the inflammatory response and ultimately contribute to DCVS. Therefore 3-AB may be a potential therapeutic agent for DCVS.

Nitrosative Stress as a Modulator of Inflammatory Change in a Model of Takotsubo Syndrome

Previous studies have shown that patients with Takotsubo syndrome (TS) have supranormal nitric oxide signaling, and post-mortem studies of TS heart samples revealed nitrosative stress. Therefore, we first showed in a female rat model that isoproterenol induces TS-like echocardiographic changes, evidence of nitrosative stress, and consequent activation of the energy-depleting enzyme poly(ADP-ribose) polymerase-1. We subsequently showed that pre-treatment with an inhibitor of poly(ADP-ribose) polymerase-1 ameliorated contractile abnormalities. These findings thus add to previous reports of aberrant β-adrenoceptor signaling (coupled with nitric oxide synthase activation) to elucidate mechanisms of impaired cardiac function in TS and point to potential methods of treatment.

Prolonging hypothermic ischaemic cardiac and vascular storage by inhibiting the activation of the nuclear enzyme poly(adenosine diphosphate-ribose) polymerase

OBJECTIVES

Heart transplantation is the standard treatment in end-stage heart failure and at shortage of cardiac allografts is its major limiting factor. Striving to optimize the use of this limited resource, the aspect that long distance procurement may increase the available donor pool must be taken into consideration. As poly(ADP-ribose)polymerase (PARP)-activation has been identified as a key pathway of reperfusion injury, we assessed the hypothesis that its inhibition would allow an extension of cold preservation time and protect the graft against ischaemia/reperfusion injury.

METHODS

Hearts from donor rats were explanted, stored in a preservation solution (Custodiol) at 4 °C for 4 h or 8 h, and heterotopically transplanted. A vehicle or the PARP-inhibitor, INO-1001 (5 mg/kg), was administered during the reperfusion period. We evaluated post-transplant graft function with a Millar micromanometer at different left-ventricular volumes. Additionally, in organ bath experiments the effect of PARP-inhibition on endothelium-dependent and -independent vasorelaxation was evaluated after long-term cold ischaemic storage/warm reperfusion.

RESULTS

PARP-inhibition resulted in a better systolic functional recovery of grafts submitted to 4 h and 8 h ischaemia. Furthermore, INO-1001 decreased the left-ventricular end-diastolic pressure after 8 h of ischaemia. Coronary blood flow was significantly higher after PARP-inhibition in comparison to controls. Endothelium-dependent vasorelaxation was significantly better in the INO-1001-groups than in the vehicle-treated transplant groups. After 24-h hypothermic storage, treatment of aortic ring with INO-1001 during reoxygenation significantly improved endothelial dysfunction.

CONCLUSIONS

By inhibiting the PARP activation, INO-1001 can protect the graft and endothelium from the injury that is caused by prolonged cold myocardial ischaemia/reperfusion, thereby improving post-transplant graft function.

Regulation on SIRT1-PGC-1α/Nrf2 pathway together with selective inhibition of aldose reductase makes compound hr5F a potential agent for the treatment of diabetic complications

(R,E)-N-(3-(2-acetamido-3-(benzyloxy) propanamido)propyl)-2-cyano-3-(4-hydroxy phenyl)acrylamide (hr5F) was design-synthesized based on bioactivity focus strategy as a potential agent to treat diabetic complicates. With in vitro enzyme assay, it is confirmed that hr5F is an effective ALR2 inhibitor with IC₅₀ value of 2.60 ± 0.15 nM, and selectivity index of 86.0 over ALR1, which is a little bit better than the reference Epalrestat (Epa). hr5F inhibits the increase of ALR2 enzyme activity and expression in human lens epithelial cells (HLECs) induced by high glucose. By applying western blot, it was found that hr5F alleviates the high glucose-induced superoxide overproduction insults by regulating SIRT1-PGC-1α/Nrf2 pathway, together with regulating NRF-1, mtTFA, Bax/Bcl-2 to ameliorate cell apoptosis. The in vivo effects of hr5F on short term streptozocin (STZ)-induced diabetic mice confirm the same functions disclosed in vitro. All the evidences support that hr5F may serve as a promising agent in the treatment of diabetic complications with close efficacy and broader indication than the reference Epa.

Oxidative toxicity in diabetes and Alzheimer's disease: mechanisms behind ROS/ RNS generation

Reactive oxidative species (ROS) toxicity remains an undisputed cause and link between Alzheimer’s disease (AD) and Type-2 Diabetes Mellitus (T2DM). Patients with both AD and T2DM have damaged, oxidized DNA, RNA, protein and lipid products that can be used as possible disease progression markers. Although the oxidative stress has been anticipated as a main cause in promoting both AD and T2DM, multiple pathways could be involved in ROS production. The focus of this review is to summarize the mechanisms involved in ROS production and their possible association with AD and T2DM pathogenesis and progression. We have also highlighted the role of current treatments that can be linked with reduced oxidative stress and damage in AD and T2DM.

Base excision repair of oxidative DNA damage: from mechanism to disease

Reactive oxygen species continuously assault the structure of DNA resulting in oxidation and fragmentation of the nucleobases. Both oxidative DNA damage itself and its repair mediate the progression of many prevalent human maladies. The major pathway tasked with removal of oxidative DNA damage, and hence maintaining genomic integrity, is base excision repair (BER). The aphorism that structure often dictates function has proven true, as numerous recent structural biology studies have aided in clarifying the molecular mechanisms used by key BER enzymes during the repair of damaged DNA. This review focuses on the mechanistic details of the individual BER enzymes and the association of these enzymes during the development and progression of human diseases, including cancer and neurological diseases. Expanding on these structural and biochemical studies to further clarify still elusive BER mechanisms, and focusing our efforts toward gaining an improved appreciation of how these enzymes form co-complexes to facilitate DNA repair is a crucial next step toward understanding how BER contributes to human maladies and how it can be manipulated to alter patient outcomes.

Diabetic Cardiomyopathy: An Immunometabolic Perspective

The heart possesses a remarkable inherent capability to adapt itself to a wide array of genetic and extrinsic factors to maintain contractile function. Failure to sustain its compensatory responses results in cardiac dysfunction, leading to cardiomyopathy. Diabetic cardiomyopathy (DCM) is characterized by left ventricular hypertrophy and reduced diastolic function, with or without concurrent systolic dysfunction in the absence of hypertension and coronary artery disease. Changes in substrate metabolism, oxidative stress, endoplasmic reticulum stress, formation of extracellular matrix proteins, and advanced glycation end products constitute the early stage in DCM. These early events are followed by steatosis (accumulation of lipid droplets) in cardiomyocytes, which is followed by apoptosis, changes in immune responses with a consequent increase in fibrosis, remodeling of cardiomyocytes, and the resultant decrease in cardiac function. The heart is an omnivore, metabolically flexible, and consumes the highest amount of ATP in the body. Altered myocardial substrate and energy metabolism initiate the development of DCM. Diabetic hearts shift away from the utilization of glucose, rely almost completely on fatty acids (FAs) as the energy source, and become metabolically inflexible. Oxidation of FAs is metabolically inefficient as it consumes more energy. In addition to metabolic inflexibility and energy inefficiency, the diabetic heart suffers from impaired calcium handling with consequent alteration of relaxation-contraction dynamics leading to diastolic and systolic dysfunction. Sarcoplasmic reticulum (SR) plays a key role in excitation-contraction coupling as Ca²⁺ is transported into the SR by the SERCA2a (sarcoplasmic/endoplasmic reticulum calcium-ATPase 2a) during cardiac relaxation. Diabetic cardiomyocytes display decreased SERCA2a activity and leaky Ca²⁺ release channel resulting in reduced SR calcium load. The diabetic heart also suffers from marked downregulation of novel cardioprotective microRNAs (miRNAs) discovered recently. Since immune responses and substrate energy metabolism are critically altered in diabetes, the present review will focus on immunometabolism and miRNAs.

Poly(ADP-ribose)polymerase 1 inhibition protects against age-dependent endothelial dysfunction

Age-related endothelial dysfunction is closely associated with the local production of reactive oxygen species (ROS) within and in the vicinity of the vascular endothelium. Oxidant-induced DNA damage can activate the nuclear enzyme poly(ADP-ribose) polymerase 1 (PARP-1), leading to endothelial dysfunction in various pathophysiological conditions. The present study aimed to investigate the role of PARP-1 in age-dependent changes in endothelial cell function and its underlying mechanism. Wild-type (WT) and PARP-1(-/-) mice were divided into young (2 months) and old (12 months) groups. Isolated aortic rings were suspended to record isometric tension to assess endothelial function. Nitric oxide (NO) production and content in plasma were detected by spectrophotometry. Superoxide (O2(-) production was detected by dihydroethidium. Expression of PARP-1, endothelial nitric oxide synthase (eNOS), induced nitric oxide synthase (iNOS), and arginase-2 (Arg2) was assessed by western blot analysis. Endothelium-dependent relaxation in response to acetylcholine was lost in old WT, but not PARP-1(-/-), mice. Endothelium-independent vasodilation was not impaired in aging mice. Production of O2(-) was greater in aging WT mice than young or aging PARP-1(-/-) mice. eNOS expression was not affected by aging in WT or PARP-1(-/-) mice, but p-eNOS expression decreased and iNOS and Arg2 levels were upregulated only in aging WT mice. In conclusion, PARP-1 inhibition may protect against age-dependent endothelial dysfunction, potentially by regulating NO bioavailability via iNOS. Inhibition of PARP-1 may help in vascular aging prevention.

Redox imbalance and mitochondrial abnormalities in the diabetic lung

Although the lung is one of the least studied organs in diabetes, increasing evidence indicates that it is an inevitable target of diabetic complications. Nevertheless, the underlying biochemical mechanisms of lung injury in diabetes remain largely unexplored. Given that redox imbalance, oxidative stress, and mitochondrial dysfunction have been implicated in diabetic tissue injury, we set out to investigate mechanisms of lung injury in diabetes. The objective of this study was to evaluate NADH/NAD⁺ redox status, oxidative stress, and mitochondrial abnormalities in the diabetic lung. Using STZ induced diabetes in rat as a model, we measured redox-imbalance related parameters including aldose reductase activity, level of poly ADP ribose polymerase (PAPR-1), NAD⁺ content, NADPH content, reduced form of glutathione (GSH), and glucose 6-phophate dehydrogenase (G6PD) activity. For assessment of mitochondrial abnormalities in the diabetic lung, we measured the activities of mitochondrial electron transport chain complexes I to IV and complex V as well as dihydrolipoamide dehydrogenase (DLDH) content and activity. We also measured the protein content of NAD⁺ dependent enzymes such as sirtuin3 (sirt3) and NAD(P)H: quinone oxidoreductase 1 (NQO1). Our results demonstrate that NADH/NAD⁺ redox imbalance occurs in the diabetic lung. This redox imbalance upregulates the activities of complexes I to IV, but not complex V; and this upregulation is likely the source of increased mitochondrial ROS production, oxidative stress, and cell death in the diabetic lung. These results, together with the findings that the protein contents of DLDH, sirt3, and NQO1 all are decreased in the diabetic lung, demonstrate that redox imbalance, mitochondrial abnormality, and oxidative stress contribute to lung injury in diabetes.

Mitochondrial dysfunction and diabetic retinopathy

Mitochondrial dysfunction may predispose to the development of diabetes mellitus with the accompanying risk for developing diabetic retinopathy or may contribute directly to the diabetic metabolic dysregulation and thereby increase the risk of diabetic late complications including retinopathy. Diabetes mellitus in mitochondrial disease can lead to the development of vision threatening retinopathy, but visual acuity is often reduced secondary to neurological deficits resulting from the mitochondrial dysfunction. The relation between mitochondrial disease and diabetic retinopathy can be influenced by epigenetics where factors in the environment modify the expression of regulatory proteins coding for the elimination of reactive oxygen species.