Poly (ADP-ribose) polymerase mediates diabetes-induced retinal neuropathy

In diabetic male Wistar rats, quercetin-conjugated superparamagnetic iron oxide nanoparticles have an effect on the SIRT1/p66Shc-mediated pathway related to cognitive impairment

BACKGROUND

Quercetin (QC) possesses a variety of health-promoting effects in pure and in conjugation with nanoparticles. Since the mRNA-SIRT1/p66Shc pathway and microRNAs (miRNAs) are implicated in the oxidative process, we aimed to compare the effects of QC and QC-conjugated superparamagnetic iron oxide nanoparticles (QCSPIONs) on this pathway.

METHODS

Through the use of the chemical coprecipitation technique (CPT), SPIONs were synthesized, coated with dextran, and conjugated with quercetin. Adult male Wistar rats were given intraperitoneal injections of streptozotocin to look for signs of type 1 diabetes (T1D). The animals were randomized into five groups: the control group got deionized water (DI), free QC solution (25 mg/kg), SPIONs (25 mg/kg), and QCSPIONs (25 mg/kg), and all groups received repeat doses administered orally over 35 days. Real-time quantitative PCR was used to assess the levels of miR-34a, let-7a-p5, SIRT1, p66Shc, CASP3, and PARP1 expression in the hippocampus of diabetic rats.

RESULTS

In silico investigations identified p66Shc, CASP3, and PARP1 as targets of let-7a-5p and miR-34a as possible regulators of SIRT1 genes. The outcomes demonstrated that diabetes elevated miR-34a, p66Shc, CASP3, and PARP1 and downregulated let-7a-5p and SIRT1 expression. In contrast to the diabetic group, QCSPIONs boosted let-7a-5p expression levels and consequently lowered p66Shc, CASP3, and PARP1 expression levels. QCSPIONs also reduced miR-34a expression, which led to an upsurge in SIRT1 expression.

CONCLUSION

Our results suggest that QCSPIONs can regulate the SIRT1/p66Shc-mediated signaling pathway and can be considered a promising candidate for ameliorating the complications of diabetes.

Parthanatos participates in glutamate-mediated HT22 cell injury and hippocampal neuronal death in kainic acid-induced status epilepticus rats

AIMS

Epileptic seizures or status epilepticus (SE) can cause hippocampal neuronal death, which has detrimental effects. Parthanatos, a new form of programmed cell death, is characterized by hyperactivation of poly (ADP-ribose) polymerase-1 (PARP-1), excessive synthesis of poly ADP-ribose polymer, mitochondrial depolarization, and nuclear translocation of apoptosis-inducing factor, observed in various neurodegenerative disorders but rarely reported in epilepsy. We aimed to investigate whether parthanatos participates in the mechanism of seizure-induced hippocampal neuronal death.

METHODS

Glutamate-mediated excitotoxicity cell model was used to study the mechanism of seizure-induced cell injury. Injection of kainic acid into the amygdala was used to establish the epileptic rat model. Corresponding biochemical tests were carried out on hippocampal tissues and HT22 cells following indicated treatments.

RESULTS

In vitro, glutamate time-dependently induced HT22 cell death, accompanied by parthanatos-related biochemical events. Pretreatment with PJ34 (PARP-1 inhibitor) or small interfering RNA-mediated PARP-1 knockdown effectively protected HT22 cells against glutamate-induced toxic effects and attenuated parthanatos-related biochemical events. Application of the antioxidant N-acetylcysteine (NAC) rescued HT22 cell death and reversed parthanatos-related biochemical events. In vivo, PJ34 and NAC afforded protection against SE-induced hippocampal neuronal damage and inhibited parthanatos-related biochemical events.

CONCLUSION

Parthanatos participates in glutamate-induced HT22 cell injury and hippocampal neuronal damage in rats following epileptic seizures. ROS might be the initiating factor during parthanatos.

Neuroprotective Effects of Nicotinamide (Vitamin B3) on Neurodegeneration in Diabetic Rat Retinas

The loss of inner retinal neurons is an initial event in diabetic retinopathy. In diabetic retinas, oxidative stress is increased, which could lead to increased oxidative DNA damage. Nicotinamide is a precursor to nicotinamide adenine dinucleotide, which contributes to the DNA damage response. We investigated whether nicotinamide plays a neuroprotective role in diabetic retinal neurodegeneration in terms of DNA repair. Male Sprague Dawley rats with streptozotocin-induced diabetes were orally administered nicotinamide (500 mg/kg/day) for 4 or 12 weeks. Oxidative stress exhibited by dihydroethidium was upregulated at 4 and 12 weeks after onset of diabetes, and nicotinamide treatment reduced oxidative stress at 4 weeks after induction of diabetes. Oxidative DNA damage measured by 8-hydroxy-2′-deoxyguanosine (8-OHdG) increased at 4 and 12 weeks after induction of diabetes and decreased following nicotinamide treatment. The elevated expression of glial fibrillary acidic protein (GFAP) induced by diabetes was attenuated by nicotinamide treatment. In Western blot analysis, the increased expression of cleaved PARP-1 in diabetes was attenuated by nicotinamide treatment at 12 weeks after induction of diabetes. The diabetes-induced apoptosis of inner retinal cells detected by the TUNEL assay was reduced by nicotinamide treatment. In conclusion, nicotinamide attenuated retinal neurodegeneration in diabetes, probably by reducing oxidative DNA damage and supporting DNA repair.

Pleiotropic role of PARP1: an overview

Poly (ADP-ribose) polymerase 1 (PARP1) protein is encoded by the PARP1 gene located on chromosome 1 (1q42.12) in human cells. It plays a crucial role in post-translational modification by adding poly (ADP-ribose) (PAR) groups to various proteins and PARP1 itself by utilizing nicotinamide adenine dinucleotide (NAD +) as a substrate. Since the discovery of PARP1, its role in DNA repair and cell death has been its identity. This is evident from an overwhelmingly high number of scientific reports in this regard. However, PARP1 also plays critical roles in inflammation, metabolism, tumor development and progression, chromatin modification and transcription, mRNA stability, and alternative splicing. In the present study, we attempted to compile all the scattered scientific information about this molecule, including the structure and multifunctional role of PARP1 in cancer and non-cancer diseases, along with PARP1 inhibitors (PARPis). Furthermore, for the first time, we have classified PARP1-mediated cell death for ease of understanding its role in cell death pathways.

A Promising Combination: PACAP and PARP Inhibitor Have Therapeutic Potential in Models of Diabetic and Hypertensive Retinopathies

Diabetes and hypertension are complex pathologies with increasing prevalence nowadays. Their interconnected pathways are frequently manifested in retinopathies. Severe retinal consequences and their tight connections as well as their possible treatments are particularly important to retinal research. In the present, work we induced diabetes with streptozotocin in spontaneously hypertensive rats and treated them either with PACAP or olaparib and alternatively with both agents. Morphological and immunohistochemical analyses were carried out to describe cell-specific changes during pathologies and after different treatments. Diabetes and hypertension caused massive structural and cellular changes especially when they were elicited together. Hypertension was crucial in the formation of ONL and OPL damage while diabetes caused significant differences in retinal thickness, OPL thickness and in the cell number of the GCL. In diabetes, double neuroprotective treatment ameliorated changes of calbindin-positive cells, rod bipolar cells and dopaminergic amacrine cells. Double treatment was curative in hypertensive diabetic rat retinas, especially in the case of rod bipolar and parvalbumin-positive cells compared to untreated or single-treated retinas. Our results highlighted the promising therapeutic benefits of olaparib and PACAP in these severe metabolic retinal disorders.

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

Apocynin ameliorates NADPH oxidase 4 (NOX4) induced oxidative damage in the hypoxic human retinal Müller cells and diabetic rat retina

NADPH oxidase (NOX) is a main producers of reactive oxygen species (ROS) that may contribute to the early pathogenesis of diabetic retinopathy (DR). ROS has harmful effects on endogenous neuro-survival factors brain-derived neurotrophic factor (BDNF) and sirtuin 1 (SIRT1) are necessary for the growth and survival of the retina. The role of NOX isoforms NOX4 in triggering ROS in DR is not clear. Here we determine the protective effects of a plant-derived NOX inhibitor apocynin (APO) on NOX4-induced ROS production which may contribute to the depletion of survival factors BDNF/SIRT1 or cell death in the diabetic retinas. Human retinal Müller glial cells (MGCs) were treated with hypoxia mimetic agent cobalt chloride (CoCl₂) in the absence or presence of APO. Molecular analysis demonstrates that NOX4 is upregulated in CoCl₂-treated MGCs and in the diabetic retinas. Increased NOX4 was accompanied by the downregulation of BDNF/SIRT1 expression or in the activation of apoptotic marker caspase-3. Whereas, APO treatment downregulates NOX4 and subsequently upregulates BDNF/SIRT1 or alleviate caspase-3 expression. Accordingly, in the diabetic retina we found a positive correlation in NOX4 vs ROS (p = 0.025; R² = 0.488) and caspase-3 vs ROS (p = 0.04; R² = 0.428); whereas a negative correlation in BDNF vs ROS (p = 0.009; R² = 0.596) and SIRT1 vs ROS (p = 0.0003; R² = 0.817) respectively. Taken together, NOX4-derived ROS could be a main contributor in downregulating BDNF/SIRT1 expression or in the activation of caspase-3. Whereas, APO treatment may minimize the deleterious effects occurring due to hyperglycemia and/or diabetic mimic hypoxic condition in early pathogenesis of DR.

Kaempferol Protects Against Hydrogen Peroxide-Induced Retinal Pigment Epithelium Cell Inflammation and Apoptosis by Activation of SIRT1 and Inhibition of PARP1

Purpose: This study investigated the protective effect of Kaempferol against hydrogen peroxides (H₂O₂)-induced retinal pigment epithelium (RPE) cell oxidative stress, inflammation, and apoptosis and investigated if this protection involves modulation of poly(ADP-ribose) polymerase-1 (PARP1)/silent information regulator 1 (SIRT1) signaling pathway. Methods: ARPE-19 cells were pretreated with increasing doses of Kaempferol (10, 25, 50, 100 μM) for 24 h in Dulbecco's modified Eagle's medium/F-12 medium with or without postincubation with H₂O₂. Control cells remained untreated. Results: Kaempferol, in a dose-dependent manner, significantly increased cell survival and reduced levels of reactive oxygen species, malondialdehyde, single-stranded DNA (ssDNA), and lactate dehydrogenase but increased levels of glutathione (GSH) and manganese-superoxide dismutase (MnSOD) in H₂O₂-treated ARPE-19 cells. It also increased GSH and MnSOD in a dose-dependent manner in control + Kaempferol treated cells. At a dose of 50 μM, the most effective dose, Kaempferol also inhibited protein levels of tumor necrosis factor alpha and interleukin-6, nuclear activity and protein levels of total, acetylated, and cleaved PARP1, and increased nuclear levels and activity of SIRT1 in H₂O₂-treated cells. In parallel, it increased total nuclear levels of Nrf2 but reduced the acetylation of p53, Nrf2, nuclear factor-κB (NF-κB) p65, and forkhead transcriptional factor 1 (FOXO1). Of interest, the stimulatory role of Kaempferol in the nuclear accumulation and activation of SIRT1 and the nuclear levels of Nrf2, as well as in reducing the acetylation of Nrf2, NF-κB p65, and FOXO1, was shown in nuclei of control + Kaempferol-treated cells. Conclusion: Kaempferol protective effect against H₂O₂-induced ARPE-19 damage involves antioxidant and anti-inflammatory effects mediated, at least, by stimulating the nuclear accumulation, activation, and deacetylase ability of SIRT1 and concurrent inhibition of PARP1.

The Role of Poly(ADP-Ribose) Polymerase-1 in Cutaneous Wound Healing

Critical Issue: Chronic nonhealing wounds of the lower extremities resulting in major amputations are a major health problem worldwide. Significance: Diabetes and ischemia are two major etiologies of nonhealing wounds of the lower extremities. Hyperglycemia from diabetes and oxidative stress from ischemia activate polyadenosine diphosphate (ADP)-ribose polymerase-1 (PARP-1), which is a nuclear enzyme that is best known for its role in DNA repair. However, the exact function of PARP-1 in ischemic/diabetic wound healing has not been well studied. Recent Advances: Poly-ADP-ribose (PAR) polymer has been detected in the wound bed and many of the PARylation-related reactions (oxidative stress response, expression of inflammatory cytokines and chemokines, cell proliferation, and migration) are important in the wound healing process. However, the role of PARP-1 in wound healing and the potential of targeting PARP-1 therapeutically in wounds are only recently being elucidated, with much still unknown. This review summarizes the recent advances in this field, highlighting some of the mechanisms through which PARP-1 may affect normal wound closure. Future Directions: The review also presents a perspective on some of the downstream targets of PARP-1 that may be explored for their role in wound healing and discusses about the therapeutic potential of PARP inhibitors for wound healing.

PARP Inhibitor Protects Against Chronic Hypoxia/Reoxygenation-Induced Retinal Injury by Regulation of MAPKs, HIF1α, Nrf2, and NFκB

Purpose

In the eye, chronic hypoxia/reoxygenation (H/R) contributes to the development of a number of ocular disorders. H/R induces the production of reactive oxygen species (ROS), leading to poly(ADP-ribose) polymerase-1 (PARP1) activation that promotes inflammation, cell death, and disease progression. Here, we analyzed the protective effects of the PARP1 inhibitor olaparib in H/R-induced retina injury and investigated the signaling mechanisms involved.

Methods

A rat retinal H/R model was used to detect histologic and biochemical changes in the retina.

Results

H/R induced reductions in the thickness of most retinal layers, which were prevented by olaparib. Furthermore, H/R caused increased levels of Akt and glycogen synthase kinase-3β phosphorylation, which were further increased by olaparib, contributing to retina protection. By contrast, H/R-induced c-Jun N-terminal kinase and p38 mitogen-activated protein kinases (MAPK) phosphorylation and activation were reduced by olaparib, via mitogen-activated protein kinase phosphatase 1 (MKP-1) expression. In addition, H/R-induced hypoxia-inducible factor 1α (HIF1α) levels were decreased by olaparib, which possibly contributed to reduced VEGF expression. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) expression was slightly increased by H/R and was further activated by olaparib. Nuclear factor-κB (NFκB) was also activated by H/R through phosphorylation (Ser536) and acetylation (Lys310) of the p65 subunit, although this was significantly reduced by olaparib.

Conclusions

Olaparib reduced H/R-induced degenerative changes in retinal morphology. The protective mechanisms of olaparib most probably involved Nrf2 activation and ROS reduction, as well as normalization of HIF1α and related VEGF expression. In addition, olaparib reduced inflammation by NFκB dephosphorylation/inactivation, possibly via the PARP1 inhibition-MKP-1 activation-p38 MAPK inhibition pathway. PARP inhibitors represent potential therapeutics in H/R-induced retinal disease.

Poly (ADP-Ribose) Polymerase Inhibition for Chemotherapy-Induced Peripheral Neuropathy: A Meta-Analysis of Placebo-Controlled Trials

Background: Chemotherapy-induced peripheral neuropathy is characterized by pain, numbness, and tingling in the hands and feet and by diminished quality of life. Multiple previous studies, mostly preclinical, suggest that poly (ADP-ribose) polymerase (PARP) inhibitors may help with these symptoms. Objective: To assess the relationship between PARP inhibition and prevention/palliation of peripheral neuropathy in a clinical setting. Design: Meta-analysis of placebo-controlled clinical trials with PARP inhibitors. Setting/Subjects: We conducted 9 literature searches that included PubMed and other sources to compile fully published placebo-controlled clinical trials that tested PARP inhibitors and that reported on peripheral neuropathy. Measurements: The relative risks for neuropathy of all grades based on PARP inhibition were calculated for each trial. Each trial was weighted by its respective sample size. A forest plot was constructed. Results: Five trials, inclusive of 843 patients, met this study's eligibility criteria. Four included a concomitant PARP inhibitor (either olaparib or veliparib) and paclitaxel, a neuropathy-causing chemotherapy agent; the remaining trial evaluated long-term monotherapy with olaparib. The pooled overall relative risk for the development of neuropathy with PARP inhibition was 1.06 (95% confidence interval: 1-1.4). Conclusions: PARP inhibition does not appear to reduce the risk of chemotherapy-induced peripheral neuropathy. Whether PARP inhibitors may palliate (rather than prevent) neuropathy remains an area in need of further investigation.

The Poly(ADP-Ribose)Polymerase-1 Inhibitor 1,5-Isoquinolinediol Attenuate Diabetes-Induced NADPH Oxidase-Derived Oxidative Stress in Retina

PURPOSE

To examine the effects of poly(ADP-ribose)polymerase-1 (PARP-1) inhibitor 1,5-isoquinolinediol (IQ) on nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-derived oxidative stress in diabetic retina.

METHODS

Streptozotocin-induced diabetic rats were treated with IQ. The NADPH oxidase enzyme activity was determined by luminometer. Expression of gp^91phox, P^47phox and nitrated proteins was examined by western blot. Interaction between gp^91phox and P^47phox was determined by coimmunoprecipitation. Enzyme-linked immunosorbent assay was utilized to measure the level of retinal total antioxidant capacity. We also studied the effect of the IQ on hydrogen peroxide (H₂O₂)-induced cleavage of PARP-1 and caspase-3 in human retinal Müller glial cells.

RESULTS

Treatment of retinal Müller cells with H₂O₂-induced PARP-1 and caspase-3 cleavage that was attenuated by IQ cotreatment. Diabetes upregulated PARP-1, NADPH oxidase enzyme activity, gp^91phox, P^47phox, nitrated protein expression and interaction between gp^91phox and P^47phox, and downregulated total antioxidant capacity in the retinas compared with nondiabetic rats. Administration of IQ did not affect the metabolic status of the diabetic rats, but it significantly attenuated diabetes-induced upregulation of NADPH oxidase enzyme activity and expressions of gp^91phox, P^47phox, and nitrated proteins and interaction between gp^91phox and P^47phox. In addition, IQ ameliorated diabetes-induced downregulation of total antioxidant capacity in the retina.

CONCLUSION

PARP-1 inhibition by IQ protects diabetic retina from NADPH oxidase-derived oxidative stress. Thus, inhibition of PARP-1 could have potential therapeutic value in preventing the development of diabetic retinopathy.

Endoplasmic reticulum stress regulates oxygen-glucose deprivation-induced parthanatos in human SH-SY5Y cells via improvement of intracellular ROS

AIMS

Endoplasmic reticulum (ER) stress has been demonstrated to regulate neuronal death caused by ischemic insults via activation of apoptosis, but it still remains unclear whether ER stress participates in regulation of parthanatos, a new type of programmed cell death characterized by PARP-1 overactivation and intracellular accumulation of PAR polymer.

METHODS

we used oxygen-glucose deprivation (OGD) and human SH-SY5Y cells to simulate neuronal damage caused by ischemia.

RESULTS

Oxygen-glucose deprivation induced time-dependent death in SH-SY5Y cells, which was accompanied with upregulation of PARP-1, accumulation of PAR polymer, decline of mitochondrial membrane potentials and nuclear translocation of AIF. Pharmacological inhibition of PARP-1 with its specific inhibitor 3AB rescued OGD-induced cell death, as well as prevented PAR polymer accumulation, mitochondrial depolarization, and AIF translocation into nucleus. Similar results could be found when PARP-1 was genetically knocked down with SiRNA. These indicated that OGD triggered parthanatos in SH-SY5Y cells. Then, we found inhibition of overproduction of ROS with antioxidant NAC attenuated obviously OGD-induced parthanatos in SH-SY5Y cells, suggesting ROS regulated OGD-induced parthanatos. Additionally, OGD also induced upregulation of ER stress-related proteins. Mitigation of ER stress with chemical chaperone 4-PBA or trehalose suppressed significantly OGD-induced overproduction of ROS, PARP-1 upregulation, PAR polymer accumulation, and nuclear accumulation of AIF, and cell death in SH-SY5Y cells.

CONCLUSION

Endoplasmic reticulum stress regulates OGD-induced parthanatos in human SH-SY5Y cells via improvement of intracellular ROS.

Neurodegeneration in diabetic retinopathy: Potential for novel therapies

The complex pathology of diabetic retinopathy (DR) affects both vascular and neural tissue. The characteristics of neurodegeneration are well-described in animal models but have more recently been confirmed in the clinical setting, mostly by using non-invasive imaging approaches such as spectral domain optical coherence tomography (SD-OCT). The most frequent observations report loss of tissue in the nerve fiber layer and inner plexiform layer, confirming earlier findings from animal models. In several cases the reduction in inner retinal layers is reported in patients with little evidence of vascular lesions or macular edema, suggesting that degenerative loss of neural tissue in the inner retina can occur after relatively short durations of diabetes. Animal studies also suggest that neurodegeneration leading to retinal thinning is not limited to cell death and tissue loss but also includes changes in neuronal morphology, reduced synaptic protein expression and alterations in neurotransmission, including changes in expression of neurotransmitter receptors as well as neurotransmitter release, reuptake and metabolism. The concept of neurodegeneration as an early component of DR introduces the possibility to explore alternative therapies to prevent the onset of vision loss, including neuroprotective therapies and drugs targeting individual neurotransmitter systems, as well as more general neuroprotective approaches to preserve the integrity of the neural retina. In this review we consider some of the evidence for progressive retinal neurodegeneration in diabetes, and explore potential neuroprotective therapies.

The dual role of poly(ADP-ribose) polymerase-1 in modulating parthanatos and autophagy under oxidative stress in rat cochlear marginal cells of the stria vascularis

Oxidative stress is reported to regulate several apoptotic and necrotic cell death pathways in auditory tissues. Poly(ADP-ribose) polymerase-1 (PARP-1) can be activated under oxidative stress, which is the hallmark of parthanatos. Autophagy, which serves either a pro-survival or pro-death function, can also be stimulated by oxidative stress, but the role of autophagy and its relationship with parthanatos underlying this activation in the inner ear remains unknown. In this study, we established an oxidative stress model in vitro by glucose oxidase/glucose (GO/G), which could continuously generate low concentrations of H₂O₂ to mimic continuous exposure to H₂O₂ in physiological conditions, for investigation of oxidative stress-induced cell death mechanisms and the regulatory role of PARP-1 in this process. We observed that GO/G induced stria marginal cells (MCs) death via upregulation of PARP-1 expression, accumulation of polyADP-ribose (PAR) polymers, decline of mitochondrial membrane potential (MMP) and nuclear translocation of apoptosis-inducing factor (AIF), which all are biochemical features of parthanatos. PARP-1 knockdown rescued GO/G-induced MCs death, as well as abrogated downstream molecular events of PARP-1 activation. In addition, we demonstrated that GO/G stimulated autophagy and PARP-1 knockdown suppressed GO/G-induced autophagy in MCs. Interestingly, autophagy suppression by 3-Methyladenine (3-MA) accelerated GO/G-induced parthanatos, indicating a pro-survival function of autophagy in GO/G-induced MCs death. Taken together, these data suggested that PARP-1 played dual roles by modulating parthanatos and autophagy in oxidative stress-induced MCs death, which may be considered as a promising therapeutic target for ameliorating oxidative stress-related hearing disorders.

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The model mimicked continuous exposure to H2O2 in physiological conditions.

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GO/G induced parthanatos and autophagy in MCs.

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GO/G-induced parthanatos and autophagy are mediated by PARP-1.

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Autophagy inhibition by 3-MA sensitizes MCs to GO/G-induced parthanatos.

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PARP-1 plays a dual role by modulating parthanatos and autophagy under GO/G-induced oxidative stress in MCs.

Targeting endothelial metaflammation to counteract diabesity cardiovascular risk: Current and perspective therapeutic options

The association of obesity and diabetes, termed "diabesity", defines a combination of primarily metabolic disorders with insulin resistance as the underlying common pathophysiology. Cardiovascular disorders associated with diabesity represent the leading cause of morbidity and mortality in the Western world. This makes diabesity, with its rising impacts on both health and economics, one of the most challenging biomedical and social threats of present century. The emerging comprehension of the genes whose alteration confers inter-individual differences on risk factors for diabetes or obesity, together with the potential role of genetically determined variants on mechanisms controlling responsiveness, effectiveness and safety of anti-diabetic therapy underlines the need of additional knowledge on molecular mechanisms involved in the pathophysiology of diabesity. Endothelial cell dysfunction, resulting from the unbalanced production of endothelial-derived vascular mediators, is known to be present at the earliest stages of insulin resistance and obesity, and may precede the clinical diagnosis of diabetes by several years. Once considered as a mere consequence of metabolic abnormalities, it is now clear that endothelial dysfunctional activity may play a pivotal role in the progression of diabesity. In the vicious circle where vascular defects and metabolic disturbances worsen and reinforce each other, a low-grade, chronic, and 'cold' inflammation (metaflammation) has been suggested to serve as the pathophysiological link that binds endothelial and metabolic dysfunctions. In this paradigm, it is important to consider how traditional antidiabetic treatments (specifically addressing metabolic dysregulation) may directly impact on inflammatory processes or cardiovascular function. Indeed, not all drugs currently available to treat diabetes possess the same anti-inflammatory potential, or target endothelial cell function equally. Perspective strategies pointing at reducing metaflammation or directly addressing endothelial dysfunction may disclose beneficial consequences on metabolic regulation. This review focuses on existing and potential new approaches ameliorating endothelial dysfunction and vascular inflammation in the context of diabesity.

Ethanol-induced changes in poly (ADP ribose) polymerase and neuronal developmental gene expression

Prenatal alcohol exposure has profound effects on neuronal growth and development. Poly-ADP Ribose Polymerase (PARP) enzymes are perhaps unique in the field of epigenetics in that they directly participate in histone modifications, transcription factor modifications, DNA methylation/demethylation and are highly inducible by ethanol. It was our hypothesis that ethanol would induce PARP enzymatic activity leading to alterations in neurodevelopmental gene expression. Mouse E18 cortical neurons were treated with ethanol, PARP inhibitors, and nuclear hormone receptor transcription factor PPARγ agonists and antagonists. Subsequently, we measured PARP activity and changes in Bdnf, OKSM (Oct4, Klf4, Sox2, c-Myc), DNA methylating/demethylating factors, and Pparγ mRNA expression, promoter 5-methylcytosine (5MC) and 5-hydroxymethylcytosine (5HMC), and PPARγ promoter binding. We found that ethanol reduced Bdnf4, 9a, and Klf4 mRNA expression, and increased c-Myc expression. These changes were reversed with a PARP inhibitor. In agreement with its role in DNA demethylation PARP inhibition increased 5MC levels at the c-Myc promoter. In addition, we found that inhibition of PARP enzymatic activity increased PPARγ promoter binding, and this corresponded to increased Bdnf and Klf4 mRNA expression. Our results suggest that PARP participates in DNA demethylation and reduces PPARγ promoter binding. The current study underscores the importance of PARP in ethanol-induced changes to neurodevelopmental gene expression.

Active site fingerprinting and pharmacophore screening strategies for the identification of dual inhibitors of protein kinase C (ΡΚCβ) and poly (ADP-ribose) polymerase-1 (PARP-1)

Current clinical studies have revealed that diabetic complications are multifactorial disorders that target two or more pathways. The majority of drugs in clinical trial target aldose reductase and protein kinase C ([Formula: see text]), while recent studies disclosed a significant role played by poly (ADP-ribose) polymerase-1 (PARP-1). In light of this, the current study was aimed to identify novel dual inhibitors of [Formula: see text] and PARP-1 using a pharmaco-informatics methodology. Pharmacophore-based 3D QSAR models for these two targets were generated using HypoGen and used to screen three commercially available chemical databases to identify dual inhibitors of [Formula: see text] and PARP-1. Overall, 18 hits were obtained from the screening process; the hits were filtered based on their drug-like properties and predicted binding affinities (docking analysis). Important amino acid residues were predicted by developing a fingerprint of the active site using alanine-scanning mutagenesis and molecular dynamics. The stability of the complexes (18 hits with both proteins) and their final binding orientations were investigated using molecular dynamics simulations. Thus, novel hits have been predicted to have good binding affinities for [Formula: see text] and PARP-1 proteins, which could be further investigated for in vitro/in vivo activity.

Neuroprotection as a Therapeutic Target for Diabetic Retinopathy

Diabetic retinopathy (DR) is a multifactorial progressive disease of the retina and a leading cause of vision loss. DR has long been regarded as a vascular disorder, although neuronal death and visual impairment appear before vascular lesions, suggesting an important role played by neurodegeneration in DR and the appropriateness of neuroprotective strategies. Upregulation of vascular endothelial growth factor (VEGF), the main target of current therapies, is likely to be one of the first responses to retinal hyperglycemic stress and VEGF may represent an important survival factor in early phases of DR. Of central importance for clinical trials is the detection of retinal neurodegeneration in the clinical setting, and spectral domain optical coherence tomography seems the most indicated technique. Many substances have been tested in animal studies for their neuroprotective properties and for possible use in humans. Perhaps, the most intriguing perspective is the use of endogenous neuroprotective substances or nutraceuticals. Together, the data point to the central role of neurodegeneration in the pathogenesis of DR and indicate neuroprotection as an effective strategy for treating this disease. However, clinical trials to determine not only the effectiveness and safety but also the compliance of a noninvasive route of drug administration are needed.

Deoxypodophyllotoxin triggers parthanatos in glioma cells via induction of excessive ROS

Parthanatos is a new form of programmed cell death that is regulated by hyper-activated PARP-1, and is emerging as a new strategy to kill cancer cells. Deoxypodophyllotoxin (DPT) is a natural chemical that is found to induce cancer cell death, in which the role of parthanatos is unknown. Thus, we investigated this issue in this study by using glioma cell lines and mice model of xenograft glioma. We found that DPT induced glioma cell death in vitro and inhibited the growth of xenograft glioma in vivo, which was accompanied with parthanatos-related biochemical events including expressional upregulation of PARP-1, cytoplasmic accumulation of PAR polymer, and nuclear translocation of AIF. In vitro study revealed that genetic knockdown of PARP-1 with small interfering RNA attenuated DPT-induced elevation in the cytoplasmic PAR-polymer and the nuclear AIF, as well as protected glioma cells against the toxicity of DPT. Further, antioxidant NAC, as well as PARP-1 inhibitor 3AB, not only alleviated the overproduction of ROS caused by DPT, but also reversed the above-mentioned biochemical events, maintained mitochondrial membrane potential and rescued glioma cells death. Therefore, we demonstrated that deoxypodophyllotoxin triggered parthanatos in glioma cells via induction of excessive ROS.

Oxidative and nitrative stress in neurodegeneration

Aerobes require oxygen for metabolism and normal free radical formation. As a result, maintaining the redox homeostasis is essential for brain cell survival due to their high metabolic energy requirement to sustain electrochemical gradients, neurotransmitter release, and membrane lipid stability. Further, brain antioxidant levels are limited compared to other organs and less able to compensate for reactive oxygen and nitrogen species (ROS/RNS) generation which contribute oxidative/nitrative stress (OS/NS). Antioxidant treatments such as vitamin E, minocycline, and resveratrol mediate neuroprotection by prolonging the incidence of or reversing OS and NS conditions. Redox imbalance occurs when the antioxidant capacity is overwhelmed, consequently leading to activation of alternate pathways that remain quiescent under normal conditions. If OS/NS fails to lead to adaptation, tissue damage and injury ensue, resulting in cell death and/or disease. The progression of OS/NS-mediated neurodegeneration along with contributions from microglial activation, dopamine metabolism, and diabetes comprise a detailed interconnected pathway. This review proposes a significant role for OS/NS and more specifically, lipid peroxidation (LPO) and other lipid modifications, by triggering microglial activation to elicit a neuroinflammatory state potentiated by diabetes or abnormal dopamine metabolism. Subsequently, sustained stress in the neuroinflammatory state overwhelms cellular defenses and prompts neurotoxicity resulting in the onset or amplification of brain damage.

Animal Models of Diabetic Retinopathy

Diabetic retinopathy (DR) is one of today's main causes of blindness in numerous developed countries worldwide. The underlying pathogenesis of DR is complex and not well understood, thus impeding development of specific, effective treatment modalities. Consequently, the use of animal models of DR is of critical importance for investigating the pathogenesis of and treatment for DR. While rats and mice are the most commonly used animal models of DR, the zebrafish now appears to be a promising model. Nonhuman primates and humans have similar eye structures, and both can develop spontaneous diabetes mellitus (DM). Although various traditionally used animal models of DR undergo a number of pathological changes similar to those of human DR, several human variations, e.g. retinal neovascularization, cannot yet be fully mimicked in any existing animal model of DM. Since both the animal models and the methods chosen for inducing DR have great influence on experimental results, a clear understanding of available animal models is vital for planning an experimental design. In this review, we summarize the mechanisms, methodologies and pros and cons of the most commonly used animal models of DR.

Novel pharmacotherapies in diabetic retinopathy

This is a summary of current and emerging pharmacologic therapies utilized in the treatment of diabetic retinopathy (DR). Current therapies, such as ranibizumab, bevacizumab, triamcinolone acetonide, and fluocinolone acetonide, inhibit angiogenesis and inflammation and may be used alone or in combination with laser treatment. Emerging therapies aim to reduce oxidative stress or inhibit other signal transduction pathways, including the protein kinase C cascade and aldose reductase pathway. Future therapies may target other molecules crucial to the pathogenesis of DR, including hepatocyte growth factors and matrix metalloproteinase 9. Finally, the emergence of novel mechanisms of medication delivery may also be on the horizon.

Oxidative stress: implications for the development of diabetic retinopathy and antioxidant therapeutic perspectives

In recent decades, localized tissue oxidative stress has been implicated as a key component in the development of diabetic retinopathy (DR). Increasing evidence shows that oxidative stress caused by diabetes-induced metabolic abnormalities is the most common mechanism associated with the pathogenesis of DR for both type 1 and type 2 diabetes. Increase in intracellular reactive oxygen species (ROS) concentrations results in the activation of several mechanisms involved in the pathogenesis of DR. In particular, damage or dysfunction caused by oxidative stress still persists even after glycemia has been normalized. Despite considerable evidence showing the beneficial effects of antioxidants in preventing the development of retinopathy, results from large-scale clinical trials on classic antioxidants are somewhat ambiguous. Scavenging reactive radicals may not be the most ideal antioxidant strategy in DR. Advances in understanding the function of ROS in the development of DR can lead to the development of new therapeutic strategies based on the mechanisms of ROS generation and scavenging. Increasing amounts of data have demonstrated the promising prospect of antioxidant therapy and its beneficial effects in vision protection. Therefore, new strategies that utilize antioxidants as additive therapy should be implemented in the treatment of DR.