Xanthine oxidase activation in mild gestational hypertension

The Nitrate-Nitrite-Nitric Oxide Pathway: Potential Role in Mitigating Oxidative Stress in Hypertensive Disorders of Pregnancy

Hypertensive diseases of pregnancy (HDPs) represent a global clinical challenge, affecting 5-10% of women and leading to complications for both maternal well-being and fetal development. At the heart of these complications is endothelial dysfunction, with oxidative stress emerging as a pivotal causative factor. The reduction in nitric oxide (NO) bioavailability is a vital indicator of this dysfunction, culminating in blood pressure dysregulation. In the therapeutic context, although antihypertensive medications are commonly used, they come with inherent concerns related to maternal-fetal safety, and a percentage of women do not respond to these therapies. Therefore, alternative strategies that directly address the pathophysiology of HDPs are required. This article focuses on the potential of the nitrate-nitrite-NO pathway, abundantly present in dark leafy greens and beetroot, as an alternative approach to treating HDPs. The objective of this review is to discuss the prospective antioxidant role of nitrate. We hope our discussion paves the way for using nitrate to improve endothelial dysfunction and control oxidative stress, offering a potential therapy for managing HDPs.

Anserine and glucosamine supplementation attenuates the levels of inflammatory markers in rats with rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disorder that affects the joint synovium. Anserine is a functional dipeptide containing methylhistidine and β-alanine, and is present in the brain and skeletal muscle of birds and mammals. Glucosamine is an amino sugar used in the synthesis of glycosylated proteins and lipids. We evaluated the effects of anserine and glucosamine on RA. Rats were assigned into the control group, RA group, anserine group (1 mg/kg), glucosamine group (200 mg/kg), or anserine plus glucosamine group (anserine, 1 mg/kg + glucosamine, 200 mg/kg). Treatment was continued for 45 consecutive days and was administered orally. The serum levels of catalase, glutathione peroxidase (Gpx), superoxide dismutase (SOD), reduced glutathione (GSH), lipid peroxidation, uric acid, nitric oxide, ceruloplasmin, zinc, copper, prostaglandin E₂ (PGE₂), matrix metalloproteinase (MMP)-3, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 were assayed. The mRNA and protein levels of nuclear factor (NF)-κB and inducible nitric oxide synthase (iNOS) in synovial tissue were also determined. Anserine plus glucosamine significantly increased the catalase, SOD, Gpx, GSH, and zinc levels compared to the control, anserine, and glucosamine groups. Also, anserine plus glucosamine significantly reduced the PGE₂, MMP-3, TNF-α, IL-1β, and IL-6 levels compared to the control, anserine, and glucosamine groups. Furthermore, anserine plus glucosamine significantly reduced the mRNA and protein levels of NF-κB and iNOS compared to the control, anserine, and glucosamine groups. Therefore, supplementation of anserine plus glucosamine shows therapeutic potential for RA.

Methionine attenuates the intensity of rheumatoid arthritis by downregulating NF-κB and iNOS expression in neonatal rats

The present study investigated the anti-arthritic effects of methionine in neonatal rats. Rats were divided into four groups, with six rats in each group. The rats were administered methionine (150- or 300-mg/kg body weight) orally for 45 consecutive days. The expression levels of catalase, superoxide dismutase (SOD), reduced glutathione (GSH), lipid peroxidation, glutathione peroxidase (Gpx), prostaglandin E₂ (PGE₂), matrix metalloproteinase-3, uric acid, nitric oxide (NO), ceruloplasmin, inducible nitric oxide synthase (iNOS), and nuclear factor (NF)-κB were determined in rheumatoid arthritis-induced neonatal rats. The levels of SOD, catalase, Gpx, and GSH were substantially reduced in control rats, while the levels of other parameters were increased in control neonatal rats. However, methionine supplementation significantly increased (more than 40%) the levels of SOD, catalase, Gpx, and GSH in neonatal rats. The levels of lipid peroxidation, uric acid, ceruloplasmin, NO, and PGE₂ were significantly reduced following methionine supplementation. Furthermore, NF-κB mRNA expression was substantially reduced up to 51.7% in the 300-mg/kg methionine group, whereas the mRNA expression of iNOS was reduced up to 43.5% in the 300-mg/kg methionine group. NF-κB protein expression was substantially reduced up to 45.8% in the 300-mg/kg methionine group, whereas the protein expression of iNOS was reduced up to 45.4% in the 300-mg/kg methionine group. Taken together, these data suggest that methionine supplementation was effective against rheumatoid arthritis.

Pyrroloquinoline quinone (PQQ) has potential to ameliorate streptozotocin-induced diabetes mellitus and oxidative stress in mice: A histopathological and biochemical study

Enhanced oxidative stress and hyperglycemia are associated with diabetes mellitus (DM). As pyrroloquinoline quinone (PQQ) is known to protect cells from oxidative stress, the present study was undertaken to reveal the hitherto unknown effects of PQQ in DM and associated problems in different tissues. Forty two mice were randomly divided into six groups. Group I receiving only citrate buffer served as the normal control, while group II animals were injected with citrate buffer and PQQ at 20 mg/kg for 15 days and served as test drug control. Animals of groups III-VI were rendered diabetic by single dose of streptozotocin (STZ, 150 mg/kg body weight), following which PQQ at a dose of 5, 10 and 20 mg/kg, was injected to the animals of group IV, V and VI respectively for 15 days. At the end, alterations in serum indices such as glucose, different lipids, insulin, amylase, urea, uric acid, serum glutamate pyruvate transaminase and serum glutamate oxaloacetate transaminase; tissue antioxidants and histopathological alterations in liver, kidney and pancreas were evaluated. STZ-treated animals developed oxidative stress as indicated by a significant increase in tissue lipid peroxidation (LPO) and lipid hydroperoxide, serum glucose, total cholesterol, triglyceride and urea, with a parallel decrease in the levels of serum insulin and tissue antioxidants. When diabetic animals received different doses of PQQ, these adverse effects were ameliorated. However, 20 mg/kg of PQQ appeared to be most effective. Findings revealed for the first time that PQQ has the potential to mitigate STZ-induced DM and oxidative damage in different organs of mice, suggesting that it may ameliorate diabetes mellitus and associated problems.

Effect of green tea extract and vitamin C on oxidant or antioxidant status of rheumatoid arthritis rat model

Elevated free radical generation in inflamed joints and impaired antioxidant system has been implicated in rheumatoid arthritis (RA). Green tea extracts (GTE) have been shown to reduce inflammation in inflammatory arthritis murine model. This study investigates possible mechanisms by which vitamin C and GTE protect joints in RA rat model. This study included forty adult male rats that were divided into four groups (10 rats each); control group, collagen II induced RA group (CII), CII treated with vitamin C (CII + Vit C) and CII treated with GTE (CII + GTE) in physiology laboratory, Assiut University, Egypt. After 45 days of treatment, plasma levels of lipid peroxides (LPO), nitric oxide (NO), ceruloplasmin (CP), superoxide dismutase (SOD), uric acid (UA) and glutathione (GSH) were detected using colorimetric methods, PGE(2) using ELISA and copper (Cu) and zinc (Zn) using spectrometer. In CII group, levels of LPO, NO, PGE(2), UA, CP, Cu were higher while SOD, GSH, Zn were lower than controls. In groups treated with vitamin C and GTE, levels of SOD, GSH were increased while levels of LPO, NO, PGE(2), Cu, CP were decreased compared with CII group. Levels of UA were decreased and Zn increased in GTE treated group compared with CII group. GTE treated group showed higher Zn and low Cu levels compared with vitamin C treated group. This study suggests proper GTE and vitamin C intake may effectively normalize the impaired oxidant/antioxidant system and delaying complication of RA.

Redox signaling, vascular function, and hypertension

Accumulating evidence supports the importance of redox signaling in the pathogenesis and progression of hypertension. Redox signaling is implicated in many different physiological and pathological processes in the vasculature. High blood pressure is in part determined by elevated total peripheral vascular resistance, which is ascribed to dysregulation of vasomotor function and structural remodeling of blood vessels. Aberrant redox signaling, usually induced by excessive production of reactive oxygen species (ROS) and/or by decreases in antioxidant activity, can induce alteration of vascular function. ROS increase vascular tone by influencing the regulatory role of endothelium and by direct effects on the contractility of vascular smooth muscle. ROS contribute to vascular remodeling by influencing phenotype modulation of vascular smooth muscle cells, aberrant growth and death of vascular cells, cell migration, and extracellular matrix (ECM) reorganization. Thus, there are diverse roles of the vascular redox system in hypertension, suggesting that the complexity of redox signaling in distinct spatial spectrums should be considered for a better understanding of hypertension.

Nucleoside and nucleobase transporters of primary human cardiac microvascular endothelial cells: characterization of a novel nucleobase transporter

Levels of cardiovascular active metabolites, like adenosine, are regulated by nucleoside transporters of endothelial cells. We characterized the nucleoside and nucleobase transport capabilities of primary human cardiac microvascular endothelial cells (hMVECs). hMVECs accumulated 2-[3H]chloroadenosine via the nitrobenzylmercaptopurine riboside-sensitive equilibrative nucleoside transporter 1 (ENT1) at a V(max) of 3.4 +/- 1 pmol.microl(-1).s(-1), with no contribution from the nitrobenzylmercaptopurine riboside-insensitive ENT2. Inhibition of 2-chloroadenosine uptake by ENT1 blockers produced monophasic inhibition curves, which are also compatible with minimal ENT2 expression. The nucleobase [3H]hypoxanthine was accumulated within hMVECs (K(m) = 96 +/- 37 microM; V(max) = 1.6 +/- 0.3 pmol.microl(-1).s(-1)) despite the lack of a known nucleobase transport system. This novel transporter was dipyridamole-insensitive but could be inhibited by adenine (K(i) = 19 +/- 7 microM) and other purine nucleobases, including chemotherapeutic analogs. A variety of other cell types also expressed the nucleobase transporter, including the nucleoside transporter-deficient PK(15) cell line (PK15NTD). Further characterization of [3H]hypoxanthine uptake in the PK15NTD cells showed no dependence on Na(+) or H(+). PK15NTD cells expressing human ENT2 accumulated 4.5-fold more [3H]hypoxanthine in the presence of the ENT2 inhibitor dipyridamole than did PK15NTD cells or hMVECs, suggesting trapping of ENT2-permeable metabolites. Understanding the nucleoside and nucleobase transporter profiles in the vasculature will allow for further study into their roles in pathophysiological conditions such as hypoxia or ischemia.

Levels and interactions of plasma xanthine oxidase, catalase and liver function parameters in Nigerian children with Plasmodium falciparum infection

Elevated plasma levels of xanthine oxidase and liver function parameters have been associated with inflammatory events in several human diseases. While xanthine oxidase provides in vitro protection against malaria, its pathophysiological functions in vivo and interactions with liver function parameters remain unclear. This study examined the interactions and plasma levels of xanthine oxidase (XO) and uric acid (UA), catalase (CAT) and liver function parameters GOT, GPT and bilirubin in asymptomatic (n=20), uncomplicated (n=32), and severe (n=18) falciparum malaria children aged 3-13 years. Compared to age-matched control (n=16), significant (p<0.05) elevation in xanthine oxidase by 100-550%, uric acid by 15.4-153.8%, GOT and GPT by 22.1-102.2%, and total bilirubin by 2.3-86% according to parasitaemia (geometric mean parasite density (GMPD)=850-87100 parasites/microL) was observed in the malarial children. Further comparison with control revealed higher CAT level (16.2+/-0.5 vs 14.6+/-0.4 U/L; p<0.05) lacking significant (p>0.05) correlation with XO, but lower CAT level (13.4-5.4 U/L) with improved correlations (r=-0.53 to -0.91; p<0.05) with XO among the asymptomatic and symptomatic malaria children studied. 75% of control, 45% of asymptomatic, 21.9% of uncomplicated, and none of severe malaria children had Hb level>11.0 g/dL. Multivariate analyses further revealed significant (p<0.05) correlations between liver function parameters and xanthine oxidase (r=0.57-0.64) only in the severe malaria group. We conclude that elevated levels of XO and liver enzymes are biochemical features of Plasmodium falciparum parasitaemia in Nigerian children, with both parameters interacting differently to modulate the catalase response in asymptomatic and symptomatic falciparum malaria.

Therapeutic effects of xanthine oxidase inhibitors: renaissance half a century after the discovery of allopurinol

The prototypical xanthine oxidase (XO) inhibitor allopurinol, has been the cornerstone of the clinical management of gout and conditions associated with hyperuricemia for several decades. More recent data indicate that XO also plays an important role in various forms of ischemic and other types of tissue and vascular injuries, inflammatory diseases, and chronic heart failure. Allopurinol and its active metabolite oxypurinol showed considerable promise in the treatment of these conditions both in experimental animals and in small-scale human clinical trials. Although some of the beneficial effects of these compounds may be unrelated to the inhibition of the XO, the encouraging findings rekindled significant interest in the development of additional, novel series of XO inhibitors for various therapeutic indications. Here we present a critical overview of the effects of XO inhibitors in various pathophysiological conditions and also review the various emerging therapeutic strategies offered by this approach.

Role of reactive oxygen species in gynecologic diseases

Free radicals derived from molecular oxygen and nitrogen are highly reactive metabolites called reactive oxygen species (ROS). Cells continuously produce free radicals and ROS as part of the metabolic process. They are involved in the various functions of the reproductive system. Antioxidants are enzymes or compounds that scavenge and reduce the presence of free radicals. Normally, a balance exists between concentrations of reactive oxygen species and antioxidant scavenging systems. The disruption of the delicate balance between pro- and antioxidants results in oxidative stress. Oxidative stress has been implicated in embryo fragmentation, DNA damage, apoptosis and poor pregnancy outcome. It has also been implicated in a large number of gynecologic diseases, such as endometriosis, pre-eclampsia and maternal diabetes. The use of antioxidants may be beneficial in combating the harmful effects of oxidative stress in many of these diseases. The present review outlines the importance of these species in the pathology of various gynecologic diseases. (Reprod Med Biol 2004; 3: 177 - 199).

Oxidative stress in streptozotocin-induced diabetic rats: effects of garlic oil and melatonin

In the present study, oxidative stress in diabetic model and the effect of garlic oil or melatonin treatment were examined. Streptozotocin (60 mg/kg body weight, i.p.)-induced diabetic rats, showed a significant increase of plasma glucose, total lipids, triglyceride, cholesterol, lipid peroxides, nitric oxide and uric acid. Concomitantly, significant decreases in the levels of antioxidants ceruloplasmin, albumin and total thiols were found in the plasma of diabetic rats. Lipid peroxide levels were significantly increased in erythrocyte lysate and in homogenates of liver and kidney, while superoxide dismutase (SOD) activities were decreased in tissue homogenates of liver and kidney. Treatment of diabetic rats with garlic oil (10 mg/kg i.p.) or melatonin (200 microg/kg i.p.) for 15 days significantly increased plasma levels of total thiol, ceruloplasmin activities, albumin. Lipid peroxides, uric acid, blood glucose, total lipid, triglyceride and cholesterol were decreased significantly after treatment with garlic oil or melatonin. Nitric oxide levels were decreased significantly in rats treated with melatonin only. In erythrocytes lysate, glutathione S-transferase (GST) activities were increased significantly in rats treated with garlic oil or melatonin, while lipid peroxides decreased significantly and total thiol increased significantly in melatonin or garlic oil treatment, respectively. In liver homogenates of rats treated with garlic or melatonin, lipid peroxides were decreased significantly, and GST activities increased significantly, while SOD activities were increased significantly in liver and kidney after garlic or melatonin treatment. The results suggest that garlic oil or melatonin may effectively normalize the impaired antioxidants status in streptozotocin induced-diabetes. The effects of these antioxidants of both agents may be useful in delaying the complicated effects of diabetes as retinopathy, nephropathy and neuropathy due to imbalance between free radicals and antioxidant systems. Moreover, melatonin may be more powerful free radical scavenger than garlic oil.