Reactive oxygen species mediate abnormal contractile response to sympathetic nerve stimulation and noradrenaline in the vas deferens of chronically diabetic rats: effects of in vivo treatment with antioxidants

Neurons for Ejaculation and Factors Affecting Ejaculation

Simple Summary

Sexual dysfunctions are rarely discussed in our current society. Males experience different sexual dysfunctions, including erectile, infertility, and ejaculatory dysfunctions. In this review only the ejaculatory dysfunction will be discussed. Ejaculation is defined as the ejection of contents collectively from the vas deferens, seminal vesicle, prostate and Cowper’s glands. It is completely controlled by a population of neurons present in the lumbar spinal cord. The presence of lesion in these neurons ceases the ejaculatory behavior in males. This population of neurons was first identified in rats; however, recently it was confirmed that these neurons are present in human males as well. The issues are known as ejaculatory dysfunction. The following are the different types of ejaculatory dysfunctions: early ejaculation, ejaculation into the urinary bladder, late ejaculation and no ejaculation.

Abstract

Ejaculation is a reflex and the last stage of intercourse in male mammals. It consists of two coordinated phases, emission and expulsion. The emission phase consists of secretions from the vas deferens, seminal vesicle, prostate, and Cowper’s gland. Once these contents reach the posterior urethra, movement of the contents becomes inevitable, followed by the expulsion phase. The urogenital organs are synchronized during this complete event. The L3–L4 (lumbar) segment, the spinal cord region responsible for ejaculation, nerve cell bodies, also called lumbar spinothalamic (LSt) cells, which are denoted as spinal ejaculation generators or lumbar spinothalamic cells [Lst]. Lst cells activation causes ejaculation. These Lst cells coordinate with [autonomic] parasympathetic and sympathetic assistance in ejaculation. The presence of a spinal ejaculatory generator has recently been confirmed in humans. Different types of ejaculatory dysfunction in humans include premature ejaculation (PE), retrograde ejaculation (RE), delayed ejaculation (DE), and anejaculation (AE). The most common form of ejaculatory dysfunction studied is premature ejaculation. The least common forms of ejaculation studied are delayed ejaculation and anejaculation. Despite the confirmation of Lst in humans, there is insufficient research on animals mimicking human ejaculatory dysfunction.

Ejaculatory dysfunction in men with diabetes mellitus

Diabetes mellitus (DM) is a metabolic disorder that is characterized by elevated blood glucose levels due to absolute or relative insulin deficiency, in the background of β-cell dysfunction, insulin resistance, or both. Such chronic hyperglycemia is linked to long-term damage to blood vessels, nerves, and various organs. Currently, the worldwide burden of DM and its complications is in increase. Male sexual dysfunction is one of the famous complications of DM, including abnormal orgasmic/ejaculatory functions, desire/libido, and erection. Ejaculatory dysfunction encompasses several disorders related to DM and its complications, such as premature ejaculation, anejaculation (AE), delayed ejaculation, retrograde ejaculation (RE), ejaculatory pain, anesthetic ejaculation, decreased ejaculate volume, and decreased force of ejaculation. The problems linked to ejaculatory dysfunction may extend beyond the poor quality of life in diabetics as both AE and RE are alleged to alter the fertility potential of these patients. However, although both diabetes patients and their physicians are increasingly aware of diabetic ejaculatory dysfunction, this awareness still lags behind that of other diabetes complications. Therefore, all these disorders should be looked for thoroughly during the clinical evaluation of diabetic men. Besides, introducing the suitable option and/or maneuvers to treat these disorders should be tailored according to each case. This review aimed to explore the most important findings regarding ejaculatory dysfunction in diabetes from pre-clinical and clinical perspectives.

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.

Application Progress of Nano Silver Dressing in the Treatment of Diabetic Foot

Diabetic foot is a serious infection of the lower limbs. It is caused by diabetic neuropathy and vascular disease. It is also the primary cause of disability and death in patients with severe diabetes, so prompt treatment is essential for positive outcomes. The clinical use of nano-silver dressings can be considered to further optimize the treatment process and improve the treatment efficacy in diabetic foot patients. Nano-silver dressings have a larger contact surface and a stronger bactericidal effect when compared to ordinary silver dressings. Besides, it can be disinfected repeatedly to better wound infection control and promote wound healing. The current article discusses the pathogenesis of diabetic foot, diabetic foot dressing treatment, the application of nanotechnology in diabetic foot treatment, the efficacy evaluation of different dressings, and the practical prospects of adopting nanotechnology in the treatment of diabetic foot.

Combatting Nitrosative Stress and Inflammation with Novel Substituted Triazinoindole Inhibitors of Aldose Reductase in PC12 Cells Exposed to 6-Hydroxydopamine Plus High Glucose

Cellular redox dysregulation produced by aldose reductase (AR) in the presence of high blood sugar is a mechanism involved in neurodegeneration commonly observed in diabetes mellitus (DM) and Parkinson's disease (PD); therefore, AR is a key target for treatment of both diseases. The substituted triazinoindole derivatives 2-(3-thioxo-2H-[1,2,4]triazino[5,6-b]indol-5(3H)-yl) acetic acid (cemtirestat or CMTI) and 2-(3-oxo-2H-[1,2,4]triazino[5,6-b]indol-5(3H)-yl) acetic acid (COTI) are well-known AR inhibitors (ARIs). The neuroprotective properties of CMTI, COTI, the clinically used epalrestat (EPA), and the pyridoindole antioxidants stobadine and SMe1EC2 were all tested in the neurotoxic models produced by hyperglycemic glucotoxicity (HG, 75 mM D-glucose, 72 h), 6-hydroxydopamine (6-OHDA), and HG+6-OHDA models in PC12 cells. Cell viability decreased in all toxic models, increased by 1-5 μM EPA, and decreased by COTI at ≥ 2.5 μM. In the HG model alone, where compounds were present in the medium for 24 h after a continuous 24-h exposure to HG, cell viability was improved by 100 nM-5 μM EPA, 1-10 μM ARIs, and the antioxidants studied, but decreased by EPA at ≥ 10 μM. In the 6-OHDA model alone, where cells were treated with compounds for 24 h and further exposed to 100 μM 6-OHDA (8 h), only the antioxidants protected cell viability. In the HG+6-OHDA model, where cells were treated with all compounds (1 nM to 50 μM) for 48 h and exposed to 75 mM glucose for 24 h followed by incubation with 6-OHDA for 8 h, cell viability was protected by 100 nM-10 μM ARIs and 100-500 nM EPA, but not by antioxidants. All ARIs inhibited the HG+6-OHDA-induced increase in iNOS, IL-1β, TNF-α, 3-NT, and total oxidant status at 1-50 μM, while increased SOD, CAT, GPx, and total antioxidant status at 1-10 μM. EPA and CMTI also reduced the HG+6-OHDA-induced increase in the cellular levels of nuclear factor kB (NF-KB). The neuroprotective potential of the novel ARIs and the pyridoindole antioxidants studied constitutes a promising tool for the development of therapeutic strategies against DM-induced and PD-related neurodegeneration.

Antioxidant treatment ameliorates diabetes-induced dysfunction of the vas deferens in a rat model

Diabetes mellitus (DM) affects the male ejaculatory function. This study was designed to evaluate the role of oxidative stress in the development of diabetes-induced dysfunction of vas deferens (VD) in the rat. DM was induced by streptozotocin in 40 male Wistar rats. Subsequently, the diabetic animals were divided into three groups: DM group, DM + Eda group and DM + Tau group. These groups were administered saline, edaravone and taurine, respectively, daily for 4 weeks. Another group of ten rats served as a control group. DM was diagnosed in the 40 streptozotocin-injected rats. DM significantly reduced the VD weight. Additionally, DM induced in vitro VD hypercontractility, VD histological abnormalities and increased the serum and VD tissue concentration of malondialdehyde. VD immunohistochemistry revealed overexpression of three markers of oxidative stress. DM significantly reduced serum testosterone levels. No live birth was documented in all DM rats in mating experiments. Antioxidants significantly improved all the aforementioned parameters, except the testosterone levels. This study indicates a deleterious impact of DM-induced oxidative stress on VD histological and functional features. Antioxidant treatment may provide an adjunct tool to alleviate ejaculatory disorders for male patients with type 1 diabetes.

Autonomic neuropathy in experimental models of diabetes mellitus

Autonomic neuropathy complicates diabetes by increasing patient morbidity and mortality. Surprisingly, considering its importance, development and exploitation of animal models has lagged behind the wealth of information collected for somatic symmetrical sensory neuropathy. Nonetheless, animal studies have resulted in a variety of insights into the pathogenesis, neuropathology, and pathophysiology of diabetic autonomic neuropathy (DAN) with significant and, in some cases, remarkable correspondence between rodent models and human disease. Particularly in the study of alimentary dysfunction, findings in intrinsic intramural ganglia, interstitial cells of Cajal and the extrinsic parasympathetic and sympathetic ganglia serving the bowel vie for recognition as the chief mechanism. A body of work focused on neuropathologic findings in experimental animals and human subjects has demonstrated that axonal and dendritic pathology in sympathetic ganglia with relative neuron preservation represents one of the neuropathologic hallmarks of DAN but it is unlikely to represent the entire story. There is a surprising selectivity of the diabetic process for subpopulations of neurons and nerve terminals within intramural, parasympathetic, and sympathetic ganglia and innervation of end organs, afflicting some while sparing others, and differing between vascular and other targets within individual end organs. Rather than resulting from a simple deficit in one limb of an effector pathway, autonomic dysfunction may proceed from the inability to integrate portions of several complex pathways. The selectivity of the diabetic process appears to confound a simple global explanation (e.g., ischemia) of DAN. Although the search for a single unifying pathogenetic hypothesis continues, it is possible that autonomic neuropathy will have multiple pathogenetic mechanisms whose interplay may require therapies consisting of a cocktail of drugs. The role of multiple neurotrophic substances, antioxidants (general or pathway specific), inhibitors of formation of advanced glycosylation end products and drugs affecting the polyol pathway may be complex and therapeutic elements may have both salutary and untoward effects. This review has attempted to present the background and current findings and hypotheses, focusing on autonomic elements including and beyond the typical parasympathetic and sympathetic nervous systems to include visceral sensory and enteric nervous systems.

Carbonyl stress in aging process: role of vitamins and phytochemicals as redox regulators

There is a growing scientific agreement that the cellular redox regulators such as antioxidants, particularly the natural polyphenolic forms, may help lower the incidence of some pathologies, including metabolic diseases like diabetes and diabesity, cardiovascular and neurodegenerative abnormalities, and certain cancers or even have anti-aging properties. The recent researches indicate that the degree of metabolic modulation and adaptation response of cells to reductants as well as oxidants establish their survival and homeostasis, which is linked with very critical balance in imbalances in cellular redox capacity and signaling, and that might be an answer the questions why some antioxidants or phytochemicals potentially could do more harm than good, or why some proteins lose their function by increase interactions with glyco- and lipo-oxidation mediates in the cells (carbonyl stress). Nonetheless, pursue of healthy aging has led the use of antioxidants as a means to disrupt age-associated physiological dysfunctions, dysregulated metabolic processes or prevention of many age-related diseases. Although it is still early to define their exact clinical benefits for treating age-related disease, a diet rich in polyphenolic or other forms of antioxidants does seem to offer hope in delaying the onset of age-related disorders. It is now clear that any deficiency in antioxidant vitamins, inadequate enzymatic antioxidant defenses can distinctive for many age-related disease, and protein carbonylation can used as an indicator of oxidative stress associated diseases and aging status. This review examines antioxidant compounds and plant polyphenols as redox regulators in health, disease and aging processes with hope that a better understanding of the many mechanisms involved with these distinct compounds, which may lead to better health and novel treatment approaches for age-related diseases.

Undernutrition affects cell survival, oxidative stress, Ca2+ handling and signaling pathways in vas deferens, crippling reproductive capacity

Background

The aim of this work was to investigate the mechanisms by which chronic malnutrition (CM) affects vas deferens function, leading to compromised reproductive capacity. Previous studies have shown that maternal malnutrition affects the reproductive tracts of adult male offspring. However, little is known about the effects of CM, a widespread life-long condition that persists from conception throughout growth to adult life.

Methodology/Principal Findings

Young adult male rats, which were chronically malnourished from weaning, presented decreased total and haploid cells in the vas deferens, hypertrophy of the muscle layer in the epididymal portion of the vas deferens and intense atrophy of the muscular coat in its prostatic portion. At a molecular level, the vas deferens tissue of CM rats exhibited a huge rise in lipid peroxidation and protein carbonylation, evidence of an accentuated increase in local reactive oxygen species levels. The kinetics of plasma membrane Ca²⁺-ATPase activity and its kinase-mediated phosphorylation by PKA and PKC in the vas deferens revealed malnutrition-induced modifications in velocity, Ca²⁺ affinity and regulation of Ca²⁺ handling proteins. The severely crippled content of the 12-kDa FK506 binding protein, which controls passive Ca²⁺ release from the sarco(endo) plasmic reticulum, revealed another target of malnutrition related to intracellular Ca²⁺ handling, with a potential effect on forward propulsion of sperm cells. As a possible compensatory response, malnutrition led to enhanced sarco(endo) plasmic reticulum Ca²⁺-ATPase activity, possibly caused by stimulatory PKA-mediated phosphorylation.

Conclusions/Significance

The functional correlates of these cellular and molecular hallmarks of chronic malnutrition on the vas deferens were an accentuated reduction in fertility and fecundity.

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.

Ejaculatory dysfunction in streptozotocin-induced diabetic rats: the role of testosterone

Hyperglycemic and hypoinsulinemic states caused by diabetes mellitus are usually related to some type of sexual dysfunction, resulting in infertility in humans and experimental models, mostly due to their effects on ejaculatory function. This study aimed to evaluate the possible role of testosterone in the restoration of normal ejaculatory function in diabetic rats. Male Wistar rats were randomly allocated into 3 experimental groups: control, diabetic (streptozotocin), and diabetic with testosterone supplementation (streptozotocin plus testosterone). The following parameters were assessed at the end of the experiment: body weight, circulating testosterone levels, number of spermatozoa ejaculated in the uterus through natural mating, and weight and in vitro isometric contractions of the vas deferens. Diabetic rats showed reduced plasma testosterone levels and ejaculatory dysfunction as observed by a lack in the spermatozoa ejaculated into the uterus of receptive females. In these diabetic rats, no difference was observed in the sensitivity of the vas deferens to norepinephrine, with or without the presence of the cocktail (cocaine plus propranolol). In spite of this, an increased sensitivity to methoxamine through the α1-adrenoceptor was observed. Testosterone supplementation did not restore these parameters to control values.We conclude that, in this experimental model, the lack of testosterone was not directly related to the diabetes-induced ejaculatory dysfunction.

Chronic treatment with D-chiro-inositol prevents autonomic and somatic neuropathy in STZ-induced diabetic mice

AIM

D-chiro-inositol (DCI) has been shown to prevent and reverse endothelial dysfunction in diabetic rats and rabbits. The present study evaluates the preventive effect of DCI on experimental diabetic neuropathy (DN).

METHODS

Streptozotocin-induced (STZ) diabetic mice were treated by oral gavage for 60 days with DCI (20 mg/kg/12 h) or saline (NaCl 0.9%; 0.1 ml/10 g/12 h; Diab) and compared with euglycaemic groups treated with saline (0.1 ml/10 g/12 h; Eugly). We compared the response of the isolated sciatic nerve, corpora cavernosa or vas deferens to electrical stimulation.

RESULTS

The electrically evoked compound action potential of the sciatic nerve was greatly blunted by diabetes. The peak-to-peak amplitude (PPA) was decreased from 3.24 ± 0.7 to 0.9 ± 0.2 mV (p < 0.05), the conduction velocity (CV) of the first component was reduced from 46.78 ± 4.5 to 26.69 ± 3.8 ms (p < 0.05) and chronaxy was increased from 60.43 ± 1.9 to 69.67 ± 1.4 ms (p < 0.05). These parameters were improved in nerves from DCI-treated mice (p < 0.05). PPA in the DCI group was 5.79 ± 0.8 mV (vs. 0.9 ± 0.2 mV-Diab; p < 0.05) and CV was 45.91 ± 3.6 ms (vs. 26.69 ± 3.8 ms-Diab; p < 0.05). Maximal relaxation of the corpus cavernosum evoked by electrical stimulation (2-64 Hz) in the Diab group was 36.4 ± 3.8% compared to 65.4 ± 2.8% in Eugly and 59.3 ± 5.5% in the DCI group (p < 0.05). Maximal contraction obtained in the vas deferens was 38.0 ± 9.2% in Eugly and 11.5 ± 2.6% in Diab (decrease of 69.7%; p < 0.05), compared to 25.2 ± 2.3% in the DCI group (p < 0.05 vs. diabetic). Electron microscopy of the sciatic nerves showed prevention of neuronal damage.

CONCLUSIONS

DCI has a neuroprotective action in both autonomic and somatic nerves in STZ-induced DN.

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.

Localization of NADPH oxidase in sympathetic and sensory ganglion neurons and perivascular nerve fibers

Superoxide anion (O(2)(-*)) production was previously reported to be increased in celiac ganglia (CG) during DOCA-salt hypertension, possibly via activation of the reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase. This suggested a role for neuronal NADPH oxidase in autonomic neurovascular control. However, the expression and localization of NADPH oxidase in the peripheral neurons are not fully known. The purpose of this study was to examine the subcellular localization of NADPH oxidase in sympathetic and sensory ganglion neurons and perivascular nerve fibers. In rat CG, p22(phox) and neuropeptide Y (NPY) were colocalized in all neurons. P22(phox) was also localized to dorsal root ganglia (DRG) neurons that contain calcitonin gene related peptide (CGRP). In mesenteric arteries, p22(phox) and p47(phox) were colocalized with NPY or CGRP in perivascular nerve terminals. A similar pattern of nerve terminal staining of p22(phox) and p47(phox) was also found in cultured CG neurons and nerve growth factor (NGF)-differentiated PC12 cells. These data demonstrate a previously uncharacterized localization of NADPH oxidase in perivascular nerve fibers. The presence of a O(2)(-*)-generating enzyme in close vicinity to the sites of neurotransmitter handling in the nerve fibers suggests the possibility of novel redox-mediated mechanisms in peripheral neurovascular control.

Effects of vitamin E and sodium selenate on impaired contractile activity by bacterial lipopolysaccharide in the rat vas deferens

We investigated whether bacterial lipopolysaccharide (LPS) treatment causes any hyporeactivity in rat vas deferens tissue and also whether vitamin E or sodium selenate has any restorative effect on this possible hyporesponsiveness. LPS treatment attenuated contractions to electrical field stimulation (EFS), phenylephrine, or ATP at the prostatic and epididymal ends. Treatment with the inducible nitric oxide synthase (iNOS) inhibitor aminoguanidine or vitamin E could prevent the impairment in contractile responses of both ends to EFS and phenylephrine but sodium selenate could restore these impaired contractions at only the epididymal end. LPS treatment also caused a similar significantly impairment on purinergic or adrenergic component of nerve-evoked contractions in the presence of prazosin or suramin, respectively, and vitamin E or sodium selenate could restored this impairment at both ends. On the other hand, both antioxidant agents failed to restore the impaired ATP-induced contractions in LPS-treated rats at both ends. In conclusion, LPS-treatment caused a hyporeactivity in the rat vas deferens. A possible increased oxidative activity in the vas deferens may be a major reason for the impairment of contractile responses. The restorative effects of vitamin E and/or sodium selenate on this hypocontractility may depend on their antioxidant properties or their inhibitory action on the iNOS.

Impaired purinergic neurotransmission to mesenteric arteries in deoxycorticosterone acetate-salt hypertensive rats

Sympathetic nerves release norepinephrine and ATP onto mesenteric arteries. In deoxycorticosterone acetate (DOCA)-salt hypertensive rats, there is increased arterial sympathetic neurotransmission attributable, in part, to impaired prejunctional regulation of norepinephrine release. Prejunctional regulation purinergic transmission in hypertension is less well understood. We hypothesized that alpha(2)-adrenergic receptor dysfunction alters purinergic neurotransmission to arteries in DOCA-salt hypertensive rats. Mesenteric artery preparations were maintained in vitro, and intracellular electrophysiological methods were used to record excitatory junction potentials (EJPs) from smooth muscle cells. EJP amplitude was reduced in smooth muscle cells from DOCA-salt (4+/-1 mV) compared with control arteries (9+/-1 mV; P<0.05). When using short trains of stimulation (0.5 Hz; 5 pulses), the alpha(2)adrenergic receptor antagonist yohimbine (1 micromol/L) potentiated EJPs in control more than in DOCA-salt arteries (180+/-35% versus 86+/-7%; P<0.05). Norepinephrine (0.1 to 3.0 micromol/L), the alpha(2)adrenergic receptor agonist UK 14304 (0.001 to 0.100 micromol/L), the A(1) adenosine receptor agonist cyclopentyladensosine (0.3 to 100.0 micromol/L), and the N-type calcium channel blocker omega-conotoxin GVIA (0.0003 to 0.1000 micromol/L) decreased EJP amplitude equally well in control and DOCA-salt arteries. Trains of stimuli (10 Hz) depleted ATP stores more completely, and the latency to EJP recovery was longer in DOCA-salt compared with control arteries. These data indicate that there is reduced purinergic input to mesenteric arteries of DOCA-salt rats because of decreased ATP bioavailability in sympathetic nerves. These data highlight the potential importance of impaired purinergic regulation of arterial tone as a target for drug treatment of hypertension.

Protein kinase C beta inhibitors: a new therapeutic target for diabetic nephropathy and vascular complications

Diabetic nephropathy (DN) has emerged as the major causative pathology in patients entering end-stage renal disease (ESRD) worldwide and it is responsible for 30-40% of all ESRD cases. Treatments for DN are centered on control of hyperglycemia and blood pressure control. However, current therapeutic regimens have not yet provided satisfactory prevention from the onset of DN. Protein kinase C (PKC) is an intracellular signaling molecule and activation of it plays an important role in the development of diabetic complications. In numerous experimental and clinical studies, inhibition of PKC (LY333531) has been shown to delay/halt the progression of diabetic complications. Presently, the drug is submitted in USA-FDA for new drug application in moderate to severe diabetic retinopathy. This review selectively discusses the role of PKC in DN and therapeutic effects produced by PKC inhibitors in DN. The role of PKC inhibitor in other diabetic complications is also discussed.

Role of lipids and fatty acids in macrosomic offspring of diabetic pregnancy

Diabetic pregnancy frequently results in macrosomia or fetal obesity. It seems that the anomalies in carbohydrate and lipid metabolism in macrosomic infants of diabetic mothers are due to maternal hyperglycemia, which leads to fetal hyperinsulinemia. We have developed a rat model of macrosomic offspring and assessed the onset of obesity in these animals. The macrosomic offspring born to diabetic mothers are prone to the development of glucose intolerance and obesity as a function of age. It seems that in utero programming during diabetic pregnancy creates a "metabolic memory" which is responsible for the development of obesity in macrosomic offspring. We have demonstrated that the metabolism of lipids, and altered anti-oxidant status and immune system are implicated in the etiopathology of obesity in these animals. We have reported beneficial effects of n-3 polyunsaturated fatty acids (PUFAs) in obese animals, born to diabetic dams.

Effects of stobadine and vitamin E in diabetes-induced retinal abnormalities: involvement of oxidative stress

BACKGROUND

Because hyperglycemia-induced oxidative stress may be a cause of retinopathy, this study examined the hypothesis that administration of exogenous antioxidants, stobadine (ST) and vitamin E (vitE), can restore retinal abnormalities in experimental diabetes.

METHODS

Normal and streptozotocin (STZ)-induced male Wistar rats received daily intraoral doses of ST (24.7 mg/kg) and vitE (alpha-dl-tocopherol acetate, 400-500 IU/kg) individually or in combinations for 8 months. The biochemical parameters including aldose reductase enzyme (AR) activity and lipid peroxidation (MDA), and histopathological changes such as retinal capillary basement membrane thickness (RCBMT) and vascular endothelial growth factor (VEGF) expression were evaluated.

RESULTS

A 37.99% increase in RCBMT was observed in rats after 8 months diabetes duration. The increase in RCBMT was 12.34% in diabetic rats treated with ST and 23.07% in diabetic rats treated with vitE. In diabetic rats treated with antioxidant combination, just a 4.38% increase was observed in RCBMT. The excess VEGF immunoreactivity and increased MDA and AR activity determined in diabetic retina were significantly attenuated by individual antioxidant treatments. Although both antioxidants decreased blood glucose, HbA1c, fructosamine and triglyceride levels in diabetic rats, poor glycemic control was maintained in all experimental groups during the treatment period. However, the antioxidant combination led to almost complete amelioration in retinal MDA and RCBMT in diabetic rats.

CONCLUSIONS

The ability of antioxidant combination to arrest retinal abnormalities and lipid peroxidation even in the presence of poor glycemic control might advocate the key role of direct oxidative damage and the protective action of antioxidants in retinal alterations associated with diabetic retinopathy.

Effects of antioxidant stobadine on protein carbonylation, advanced oxidation protein products and reductive capacity of liver in streptozotocin-diabetic rats: role of oxidative/nitrosative stress

BACKGROUND

Increased oxidative/nitrosative stress is important in the pathogenesis of diabetic complications, and the protective effects of antioxidants are a topic of intense research. The purpose of this study was to investigate whether a pyridoindole antioxidant stobadine (STB) have a protective effect on tissue oxidative protein damage represented by the parameters such as protein carbonylation (PC), protein thiol (P-SH), total thiol (T-SH) and non-protein thiol (Np-SH), nitrotyrosine (3-NT), and advanced oxidation protein products (AOPP) in streptozotocin-diabetic rats.

METHODS

Diabetes was induced in male Wistar rats by intraperitonal injection of streptozotocin (55 mg/kg). Some of the non-diabetic (control) and diabetic rats treated with STB (24.7 mg/kg/day) during 16 weeks, and the effects on blood glucose, PC, AOPP, 3-NT, P-SH, T-SH and Np-SH were studied. Biomarkers were assayed by enzyme-linked immunosorbent assay (ELISA) or by colorimetric methods.

RESULTS

Administration of stobadine to diabetic animals lowered elevated blood glucose levels by approximately 16% relative to untreated diabetic rats. Although stobadine decreased blood glucose, poor glycemic control was maintained in stobadine treated diabetic rats during the treatment period. Biochemical analyses of liver proteins showed significant diminution of sulfhydryl groups, P-SH, T-SH, Np-SH, and elevation of carbonyl groups in diabetic animals in comparison to healthy controls. As a biomarker of nitrosative stress, 3-NT levels did not significantly change by diabetes induction or by stobadine treatment when compared to control animals. However, the treatment with stobadine resulted in a significant decrease in PC, AOPP levels and normalized P-SH, T-SH, Np-SH groups in liver of diabetic animals.

CONCLUSIONS

The results are in accordance with the pro-oxidant role of chronic hyperglycemia, and the ability of stobadine to attenuate protein oxidation and improving tissue reductive capacity may account, at least partly for its observed beneficial effects on tissue function in diabetes.