Stobadine protects rat kidney against ischaemia/reperfusion injury

Cemtirestat, an aldose reductase inhibitor and antioxidant compound, induces ocular defense against oxidative and inflammatory stress in rat models for glycotoxicity

Fructose, endogenously produced as a consequence of activation of the polyol pathway under hyperglycemic conditions, contribute to formation of advanced glycoxidation end products (AGEs) and carbonyl stress. Oxidative stress is increased in diabetes (DM) due to AGEs formation and the utilization of NADPH by aldo-keto reductase, AKR1B1(AR), the first enzyme in polyol pathway. Since inhibition of AR is an attractive approach for the management of diabetic eye diseases, we aimed to compare the effects of a novel AR inhibitor (ARI)/antioxidant (AO) compound cemtirestat on eye tissues with the effects of ARI drug epalrestat and AO agent stobadine in rat model for glycotoxicity. One group of rats was fed high fructose (10% drinking water; 14 weeks), while type-2 DM was induced in the other group of rats with fructose plus streptozotocin (40 mg/kg-bw/day). Diabetic (D) and nondiabetic fructose-fed rats (F) were either untreated or treated with two different doses of cemtirestat (2.5 and 7.5 mg/kg-bw/day), epalrestat (25 and 50 mg/kg-bw/day), or stobadine (25 and 50 mg/kg-bw/day) for 14 weeks. Cemtirestat, epalrestat, and stobadine elaviate the increase in TNF-α, IL-1β, NF-ƙB, and caspase-3 in retina, lens, cornea, and sclera of F and D rats. Both glycotoxicity models resulted in a decrease in GSH to GSSG ratio and a change in glutathione S-transferase activity in eye tissues, but these alterations were improved especially with cemtirestat and stobadine. Lens D-sorbitol of D rats increased more than that of F rats, this increase was only attenuated by cemtirestat and epalrestat. Epalrestat was more effective than cemtirestat and stobadine in inhibiting the increase of vascular endothelial growth factor (VEGF) in the retina of F and D rats. Cemtirestat and stobadine but not epalrestat decreased high level of Nε-(carboxymethyl)lysine in the lens and retina of F and D rats. Cemtirestat is a potential therapeutic in protecting the rat eye against glycotoxicity insults.

An old mobbing story and COVID-19

Innovative medical education greatly relies on lifelong learning with universal standards in research, for generating novel knowledge for improvement maximum patient care. The other side of innovative medical education relies on success of development of novel ideas, perspective; skill building, future career objectives. Leaders have curious roles in the research assistant education. In the current century, both technology and education raced forward in many countries. Mobbing and bullying is an important problem in all fields, every sphere of life in workplaces. Unethical behavior must not take place in universities because universities are the centers of learning, and best academic teaching in ethical standards. Bullying may damage every individual in every academic degree and effect academic performance. In this paper I will discuss a mobbing case which is done to a young academician in many years ago, which is not most frequently observed type. However, such bullying behaviors may increase due to COVID-19 pandemic. Because COVID-19 pandemic may cause various problems in social groups difficulties, anxiety, and economic challenges, problems. Nowadays everybody is experiencing worry, uncertainty, anxiety, fear of economic problems, fear of dying. COVID-19 pandemic has created some unexpected problems to everybody however, academic researchers have additional worries and fears such as; the expiration time of chemicals, problems on chemicals are not imported from abroad on time also difficulties of knockout or transgenic experimental animals cannot be imported from abroad on time, and all these problems cause fear of unsuccessful experimental results, spending extra time. All these anxieties may cause arouse increasing unstable friendships and mobbing possibilities. The COVID-19 disease takes our future and experimental plans to waste basket and change everything including friendship.

Development of Novel Indole-Based Bifunctional Aldose Reductase Inhibitors/Antioxidants as Promising Drugs for the Treatment of Diabetic Complications

Aldose reductase (AR, ALR2), the first enzyme of the polyol pathway, is implicated in the pathophysiology of diabetic complications. Aldose reductase inhibitors (ARIs) thus present a promising therapeutic approach to treat a wide array of diabetic complications. Moreover, a therapeutic potential of ARIs in the treatment of chronic inflammation-related pathologies and several genetic metabolic disorders has been recently indicated. Substituted indoles are an interesting group of compounds with a plethora of biological activities. This article reviews a series of indole-based bifunctional aldose reductase inhibitors/antioxidants (ARIs/AOs) developed during recent years. Experimental results obtained in in vitro, ex vivo, and in vivo models of diabetic complications are presented. Structure–activity relationships with respect to carboxymethyl pharmacophore regioisomerization and core scaffold modification are discussed along with the criteria of ‘drug-likeness”. Novel promising structures of putative multifunctional ARIs/AOs are designed.

Protective Effects of Novel Substituted Triazinoindole Inhibitors of Aldose Reductase and Epalrestat in Neuron-like PC12 Cells and BV2 Rodent Microglial Cells Exposed to Toxic Models of Oxidative Stress: Comparison with the Pyridoindole Antioxidant Stobadine

Aldose reductase (AR) catalyzes the conversion of glucose to sorbitol in a NADPH-dependent reaction, thereby increasing the production of reactive oxygen species (ROS). Since AR activation is linked to redox dysregulation and cell damage in neurodegenerative diseases, AR inhibitors (ARIs) constitute promising therapeutic tools for the treatment of these disorders. Among these compounds, the novel substituted triazinoindole derivatives cemtirestat (CMTI) and COTI, as well as the clinically employed epalrestat (EPA) and the pyridoindole-antioxidant stobadine (STB), were tested in both PC12 cells and BV2 microglia exposed to four different neurotoxic models. These include (1) oxidative stress with hydrogen peroxide (H₂O₂), (2) mitochondrial complex IV inhibition with NaN₃, (3) endoplasmic reticulum-stress and lipotoxicity induced by palmitic acid/bovine serum albumin (PAM/BSA), and (4) advanced carbonyl compound lipotoxicity by 4-hydroxynonenal (4-HNE). All toxic compounds decreased cell viability and increased ROS formation in both PC12 and BV2 cells in a concentration-dependent manner (1-1000 μM; NaN₃ < H₂O₂≈PAM/BSA < 4-HNE). In PC12 cells, EPA increased cell viability in all toxic models only at 1 μM, whereas CMTI restored baseline viability in all toxic models. COTI afforded protection against lipotoxicity, while STB only prevented H₂O₂-induced toxicity. Except for the 4-HNE model, EPA prevented ROS generation in all other toxic models, whereas CMTI, COTI, and STB prevented ROS production in all toxic models. In BV2 cells, EPA and CMTI restored baseline cell viability in all toxic models tested, while COTI and STB did not prevent the loss of viability in the NaN₃ model. All ARIs and STB efficiently prevented ROS formation in all toxic models in a concentration-independent manner. The differential protective effects evoked by the novel ARIs and STB on the toxic models tested herein provide novel and relevant comparative evidence for the design of specific therapeutic strategies against neurodegenerative events associated with neurological disorders.

Curious Cases of the Enzymes

Life as we know it heavily relies on biological catalysis, in fact, in a very nonromantic version of it, life could be considered as a series of chemical reactions, regulated by the guarding principles of thermodynamics. In ancient times, a beating heart was a good sign of vitality, however, to me, it is actually the presence of active enzymes that counts… Though we do not usually pay attention, the history of enzymology is as old as humanity itself, and dates back to the ancient times. This paper is dedicated to these early moments of this remarkable science that touched our lives in the past and will make life a lot more efficient for humanity in the future. There was almost always a delicate, fundamentally essential relationship between mankind and the enzymes. Challenged by a very alien and hostile Nature full of predators, prehistoric men soon discovered the medicinal properties of the plants, through trial and error. In fact, they accidently discovered the enzyme inhibitors and thus, in crude terms, kindled a sparkling area of research. These plant-derivatives that acted as enzyme inhibitors helped prehistoric men in their pursuit of survival and protection from predators; in hunting and fishing… Later in history, while the underlying purposes of survival and increasing the quality of life stayed intact, the ways and means of enzymology experienced a massive transformation, as the 'trial and error' methodology of the ancients is now replaced with rational scientific theories.

Scavenging reactive oxygen species using tempol in the acute phase of renal ischemia/reperfusion and its effects on kidney oxygenation and nitric oxide levels

Background

Renal ischemia/reperfusion (I/R) injury is commonly seen in kidney transplantation and affects the allograft survival rates. We aimed to test our hypothesis that scavenging reactive oxygen species (ROS) with tempol would protect renal oxygenation and nitric oxide (NO) levels in the acute phase of renal I/R.

Methods

Rats were randomly divided: (1) no I/R, no tempol; (2) no I/R, but with tempol; (3) I/R without tempol; and (4) I/R with tempol. I/R was induced by 30-min clamping of the renal artery. Tempol (200 μmol/kg/h/i.v) was administered 15 min prior to I/R.

Results

I/R without tempol led to a significant decrease in renal oxygen delivery and microvascular oxygenation. Tempol, however, protected renal oxygenation after I/R. At R90, the creatinine clearance rate was lower in the I/R-subjected group that did not receive tempol compared to that in the other groups. I/R injury without tempol treatment led to a significant increase in tissue malondialdehyde levels and a significant decrease in tissue NO levels. Tempol administration before I/R could prevent oxidative stress and altered tissue NO levels.

Conclusions

This underscores that unbalance between oxygen, NO, and ROS forms an important component of the pathogenesis of I/R-induced AKI and should therefore be taken into account when designing a prevention/treatment strategy for renal I/R injury in transplantation.

Glucose-6-phosphate dehydrogenase deficiency and Alzheimer's disease: Partners in crime? The hypothesis

Alzheimer's disease is a multifaceted brain disorder which involves various coupled irreversible, progressive biochemical reactions that significantly reduce quality of life as well as the actual life expectancy. Aging, genetic predispositions, head trauma, diabetes, cardiovascular disease, deficiencies in insulin signaling, dysfunction of mitochondria-associated membranes, cerebrovascular changes, high cholesterol level, increased oxidative stress and free radical formation, DNA damage, disturbed energy metabolism, and synaptic dysfunction, high blood pressure, obesity, dietary habits, exercise, social engagement, and mental stress are noted among the risk factors of this disease. In this hypothesis review I would like to draw the attention on glucose-6-phosphate dehydrogenase deficiency and its relationship with Alzheimer's disease. This enzymopathy is the most common human congenital defect of metabolism and defined by decrease in NADPH+H(+) and reduced form of glutathione concentration and that might in turn, amplify oxidative stress due to essentiality of the enzyme. This most common enzymopathy may manifest itself in severe forms, however most of the individuals with this deficiency are not essentially symptomatic. To understand the sporadic Alzheimer's disease, the writer of this paper thinks that, looking into a crystal ball might not yield much of a benefit but glucose-6-phosphate dehydrogenase deficiency could effortlessly give some clues.

Age- and diabetes-induced regulation of oxidative protein modification in rat brain and peripheral tissues: consequences of treatment with antioxidant pyridoindole

The increased glyco- and lipo-oxidation events are considered one of the major factors in the accumulation of non-functional damaged proteins, and the antioxidants may inhibit extensive protein modification and nitrosylated protein levels, enhancing the oxidative damage at the cellular levels in aging and diabetes. Because of its central role in the pathogenesis of age-dependent and diabetes-mediated functional decline, we compared the levels of oxidatively modified protein markers, namely AGEs (Advanced Glycation End-protein adducts), 4-HNE (4-hydroxy-nonenal-histidine) and 3-NT (3-nitrotyrosine), in different tissues of young and old rats. Separately, these three oxidative stress parameters were explored in old rats subjected to experimentally induced diabetes and following a long-term treatment with a novel synthetic pyridoindole antioxidant derived from stobadine-SMe1EC2 (2-ethoxycarbonyl-8-methoxy-2,3,4,4a,5,9b-hexahydro-1H-pyrido[4,3-b]indolinium dichloride). Diabetes induced by streptozotocin injection in rats aged 13-15 months, and SMe1EC2 treatment was applied during 4months to aged diabetic rats. AGEs and 4-HNE levels were significantly elevated in brain, ventricle and kidney, but not in lens and liver of aged rats when compared with young rats. Diabetes propagated ageing-induced increase in AGEs and 4-HNE in brain, ventricle and kidney, and raised significantly lens and liver AGEs and 4-HNE levels in aged rats. In aged diabetic rats, SMe1EC2 protected only the kidney against increase in AGEs, and inhibited significantly 4-HNE levels in brain, kidney, liver and lens that were observed more pronounced in lens. 3-NT was significantly increased in brain of aged rats and in kidney, lens and ventricle of aged diabetic rats, while SMe1EC2 has no protective effect on 3-NT increase. Results demonstrate that (1) the responsiveness of different tissue proteins to glyco-lipo-oxidative and nitrosative stress in the course of normal aging was miscellaneous. (2) Diabetes is a major factor contributing to accelerated aging. (3) SMe1EC2 selectively inhibited the generation of oxidatively modified proteins, only in a limited number of tissues.

Apoptosis and acute kidney injury

Improved mechanistic understanding of renal cell death in acute kidney injury (AKI) has generated new therapeutic targets. Clearly, the classic lesion of acute tubular necrosis is not adequate to describe the consequences of renal ischemia, nephrotoxin exposure, or sepsis on glomerular filtration rate. Experimental evidence supports a pathogenic role for apoptosis in AKI. Interestingly, proximal tubule epithelial cells are highly susceptible to apoptosis, and injury at this site contributes to organ failure. During apoptosis, well-orchestrated events converge at the mitochondrion, the organelle that integrates life and death signals generated by the BCL2 (B-cell lymphoma 2) protein family. Death requires the 'perfect storm' for outer mitochondrial membrane injury to release its cellular 'executioners'. The complexity of this process affords new targets for effective interventions, both before and after renal insults. Inhibiting apoptosis appears to be critical, because circulating factors released by the injured kidney induce apoptosis and inflammation in distant organs including the heart, lung, liver, and brain, potentially contributing to the high morbidity and mortality associated with AKI. Manipulation of known stress kinases upstream of mitochondrial injury, induction of endogenous, anti-apoptotic proteins, and improved understanding of the timing and consequences of renal cell apoptosis will inevitably improve the outcome of human AKI.

Glycoxidative stress and cardiovascular complications in experimentally-induced diabetes: effects of antioxidant treatment

Diabetes mellitus (DM) is a common metabolic disease, representing a serious risk factor for the development of cardiovascular complications, such as coronary heart disease, peripheral arterial disease and hypertension. Oxidative stress (OS), a feature of DM, is defined as an increase in the steady-state levels of reactive oxygen species (ROS) and may occur as a result of increased free radical generation and/or decreased anti-oxidant defense mechanisms. Increasing evidence indicates that hyperglycemia is the initiating cause of the tissue damage in DM, either through repeated acute changes in cellular glucose metabolism, or through long-term accumulation of glycated biomolecules and advanced glycation end products (AGEs). AGEs are formed by the Maillard process, a non-enzymatic reaction between ketone group of the glucose molecule or aldehydes and the amino groups of proteins that contributes to the aging of proteins and to the pathological complications of DM. In the presence of uncontrolled hyperglycemia, the increased formation of AGEs and lipid peroxidation products exacerbate intracellular OS and results in a loss of molecular integrity, disruption in cellular signaling and homeostasis, followed by inflammation and tissue injury such as endothelium dysfunction, arterial stiffening and microvascular complications. In addition to increased AGE production, there is also evidence of multiple pathways elevating ROS generation in DM, including; enhanced glucose auto-oxidation, increased mitochondrial superoxide production, protein kinase C-dependent activation of NADPH oxidase, uncoupled endothelial nitric oxide synthase (eNOS) activity, increased substrate flux through the polyol pathway and stimulation of eicosanoid metabolism. It is, therefore, not surprising that the correction of these variables can result in amelioration of diabetic cardiovascular abnormalities. A linking element between these phenomena is cellular redox imbalance due to glycoxidative stress (GOS). Thus, recent interest has focused on strategies to prevent, reverse or retard GOS in order to modify the natural history of diabetic cardiovascular abnormalities. This review will discuss the links between GOS and diabetes-induced cardiovascular disorders and the effect of antioxidant therapy on altering the development of cardiovascular complications in diabetic animal models.

Time-dependent changes in serum nitric oxide levels after long bone fracture

Nitric oxide (NO) is a free radical of physiological significance. The changes in the production of NO during the fracture healing process are not well known. This clinical prospective study was planned to determine these changes in patients with fractured long bone(s), who underwent surgery in the 3rd week after fracture. The patients were divided into two groups: 20 patients with an isolated femoral fracture and 20 patients with multiple fractures, including a femoral fracture. Venous blood was drawn from the healthy volunteers (n = 20) once, and from the patients seven times during 21 days after fracture. NO level was measured as nitrite in each serum sample. The serum NO levels at all measurements of the patients were significantly higher than those of the control subjects. The time-dependent changes in the NO levels were similar in both patient groups. The serum NO levels were highest in the first 6 hrs, and then decreased to the lowest level on the 3rd day. Subsequently, there was an increasing trend on the 5th, 7th and 14th days. At all times of the measurements, the NO levels were higher in patients with multiple fractures than in those with the femoral fracture, with the significant difference observed at the 6 hrs and on the 7th day. The NO levels were decreased on the 21st day after surgery. The present study suggests that NO production may be increased in considerable amounts during the first 2 weeks of fracture healing, particularly in the first 6 hrs.

Nigella sativa protects against ischaemia/reperfusion injury in rat kidneys

BACKGROUND

Renal ischaemia followed by reperfusion leads to acute renal failure in both native kidneys and renal allografts, which is a complex pathophysiologic process involving hypoxia and free radical (FR) damage. The oil of Nigella sativa (NSO) has been subjected to considerable pharmacological investigations that have revealed its antioxidant activity in different conditions. But there is no previously reported study about its effect on ischaemia/reperfusion (I/R) injury of kidneys. The aim of this study was to investigate the possible effects of NSO in I/R-induced renal injury in rats.

METHODS

Thirty healthy male Wistar albino rats were randomly assigned to one of the following groups: control, sham, I/R, NSO+I/R, I/R+NSO and NSO. I/R, NSO+I/R and I/R+NSO rats were subjected to bilateral renal ischaemia followed by reperfusion and then all the rats were killed and kidney function tests, serum and tissue oxidants and antioxidants were determined and histopathological examinations were performed.

RESULTS

Pre- and post-treatment with NSO produced reduction in serum levels of blood urea nitrogen (BUN) and creatinine caused by I/R and significantly improved serum enzymatic activities of superoxide dismutase (SOD) and glutathion peroxidase (GSH-Px) and also tissue enzymatic activities of catalase (CAT), SOD and GSH-Px. NSO treatment resulted in lower total oxidant status (TOS) and higher total antioxidant capacity (TAC) levels and also significant reduction in serum and tissue malondialdehyde (MDA), nitric oxide (NO) and protein carbonyl content (PCC) that were increased by renal I/R injury. The kidneys of untreated ischaemic rats had a higher histopathological score, while treatment with NSO nearly preserved the normal morphology of the kidney.

CONCLUSIONS

In view of previous observations and our data, with the potent FR scavenger and antioxidant properties, NSO seems to be a highly promising agent for protecting tissues from oxidative damage and preventing organ damage due to renal I/R.

Novel pharmacological approaches to the treatment of renal ischemia-reperfusion injury: a comprehensive review

Renal ischemia-reperfusion (I-R) contributes to the development of ischemic acute renal failure (ARF). Multi-factorial processes are involved in the development and progression of renal I-R injury with the generation of reactive oxygen species, nitric oxide and peroxynitrite, and the decline of antioxidant protection playing major roles, leading to dysfunction, injury, and death of the cells of the kidney. Renal inflammation, involving cytokine/adhesion molecule cascades with recruitment, activation, and diapedesis of circulating leukocytes is also implicated. Clinically, renal I-R occurs in a variety of medical and surgical settings and is responsible for the development of acute tubular necrosis (a characteristic feature of ischemic ARF), e.g., in renal transplantation where I-R of the kidney directly influences graft and patient survival. The cellular mechanisms involved in the development of renal I-R injury have been targeted by several pharmacological interventions. However, although showing promise in experimental models of renal I-R injury and ischemic ARF, they have not proved successful in the clinical setting (e.g., atrial natriuretic peptide, low-dose dopamine). This review highlights recent pharmacological developments, which have shown particular promise against experimental renal I-R injury and ischemic ARF, including novel antioxidants and antioxidant enzyme mimetics, nitric oxide and nitric oxide synthase inhibitors, erythropoietin, peroxisome-proliferator-activated receptor agonists, inhibitors of poly(ADP-ribose) polymerase, carbon monoxide-releasing molecules, statins, and adenosine. Novel approaches such as recent research involving combination therapies and the potential of non-pharmacological strategies are also considered.