Manar A. Nader

Protective effects of propolis and thymoquinone on development of atherosclerosis in cholesterol-fed rabbits

Hypercholesterolemia, cholesterol-enriched diet and oxidative stress have been shown to increase serum total cholesterol (TC) and low density lipoprotein-cholesterol (LDL-C) levels resulting in development of atherosclerosis. Antioxidants play an important role in inhibiting and scavenging free radicals, thus providing protection to humans against infectious and degenerative diseases. The present study was undertaken to examine the possible protective effects of propolis (a resinous hive product collected by honeybees from various plant sources) and thymoquinone (TQ, active constituent of Nigella. Sativa seeds oil) on serum lipid levels and early atherosclerotic lesions in hypercholestrolemic rabbits. New Zealand rabbits were fed on either standard chow or atherogenic diet during four weeks and concomitantly received either propolis or TQ. At the end of experiment period, serum samples were collected to determine lipid profile, kidney functions and antioxidant status. Tissues from aorta, pulmonary artery and kidney were taken for histopathological examination. The cholesterol-enriched diet induced a significant increase in serum TC, triglycerides, LDL-C, thiobarbituric acid-reactive substances concentrations and a significant decrease in high density lipoprotein-cholesterol and in reduced glutathione levels compared to control group. Administration of propolis or TQ with cholesterol-enriched diet significantly (p < 0.05) reduced TC, LDL-C, triglycerides and thiobarbituric acid-reactive substances concentrations, while increased high density lipoprotein-cholesterol concentration, as well as glutathione content compared to high cholesterol (HC) control group. Kidney function parameters were significantly affected by cholesterol diet and both propolis and TQ counterregulated the cholesterol-induced changes. Histopathologically, early athersclerotic changes were observed in HC control group represented by endothelial damage and thickened foam cells while propolis or TQ provided protection against the HC-induced damage. In conclusion, the present study suggests the potential beneficial effects of both propolis and TQ in diminishing the risk of atherosclerosis via antioxidant mechanism.

Comparative evaluation of anti-inflammatory properties of thymoquinone and curcumin using an asthmatic murine model

This study was designed to compare the inhibitory effects of thymoquinone (TQ) and curcumin (CMN) on the biological changes associating asthma. TQ appeared to exhibit greater inhibitory effects on the aggregation of inflammatory cells in bronchoalveolar lavage (BAL) fluid and in lung tissues. We also measured the effects of the two agents on serum IgE and the changes in the mRNA levels of inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α) and transforming growth factor-β1 (TGF-β1). Serum IgE was significantly decreased by TQ and CMN with TQ being more potent. Also, TQ showed superior inhibitory effects on iNOS and TGF-β1. Meanwhile, CMN was more potent in inhibiting mRNA expression of TNF-α. These results suggest that TQ is more potent in inhibiting the inflammatory changes associating asthma. On the other hand, CMN was a less potent inhibitor of all measured parameters, despite its superior inhibitory effect on TNF-α mRNA levels.

Effect of betulinic acid on neutrophil recruitment and inflammatory mediator expression in lipopolysaccharide-induced lung inflammation in rats

This study aimed to evaluate the effect of betulinic acid (BA) on acute lung damage induced by bacterial endotoxin (lipopolysaccharide, LPS) in male Sprague-Dawley rats and explore its possible mechanisms. Oral administration of 25 (mg/kg) BA started 7 days before LPS or saline nasal installation. Twenty-four hours after LPS or saline installation, samples of lung tissues were collected for determination of level of lipid peroxidation (MDA), reduced glutathione (GSH), superoxide dismutase (SOD), and expression of tumor necrosis-α (TNF-α), transforming growth factor-β1 (TGF-β1) and inducible nitric oxide synthase (iNOS). Histopathology was done to examine pathological changes in lungs. Wet/dry (W/D) ratio and capillary protein leakage were also determined. Bronchoalveolar lavage (BAL) fluid was carried out for quantification of airway cellular inflammation and nitrate/nitrite (NOx) level. In comparison to BAL fluid samples from control animals, LPS-stimulated animals exhibited a higher count of the inflammatory cells and increased NOx levels. Lungs from LPS-treated animals showed increased lipid peroxidation, altered activities of antioxidant enzymes (GSH and SOD) and increased expression of TNF-α, TGF-β1 and iNOS in comparison to lungs from control animals. LPS installation-induced pulmonary edema, manifested by significant increase in lung W/D ratio and Evans blue extravasation in lung tissue. This was supported by the histopathological examination which revealed markedly inflamed lung in LPS-treated animals. Treatment with BA was found to significantly attenuate all these alterations. The present results suggest that BA is endowed with antiinflammatory and antioxidant properties that protect the lung against the deleterious actions of LPS.

Attenuation of oxidative stress-induced vascular endothelial dysfunction by thymoquinone.

This study aimed to assess the effects of thymoquinone (TQ) on pyrogallol-induced endothelial dysfunction in isolated rabbit aorta. The protective effects of TQ were examined by incubating aortic rings in TQ concomitant with pyrogallol. The results revealed that pyrogallol produced significant enhancement of phenylephrine-induced contraction and impairment of acetylcholine-induced relaxation. Pyrogallol caused a significant increase in lipid peroxidation and reduction in the level of superoxide dismutase and reduced glutathione in the aortic homogenates. In addition, pyrogallol produced a significant decrease in nitrite/nitrate concentrations (NOx), constitutive nitric oxide synthase (cNOS) activity and an increase in inducible nitric oxide synthase (iNOS) activity in the aortic homogenates. These changes were counteracted by TQ co-incubation as TQ attenuated pyrogallol-induced impairment in vascular reactivity in a dose-dependent manner. Furthermore, TQ showed potent antioxidant activity as well as causing a significant increase in NOx and cNOS activity, and depression in iNOS activity. These results suggest that TQ can protect against pyrogallol-induced endothelial dysfunction which probably results from its potent antioxidant capacity that leads to an increase in NO production as well as its ability to enhance the generation and bioavailability of NO.

Inhibition of anaphylaxis like reaction and mast cell activation by Sitagliptin

Mast cells stimulation activates degranulation process resulting in releasing of mediators, such as histamine. In this study, the effect of aqueous extract of sitagliptin, a selective dipeptidylpeptidase-4 inhibitor, on the mast cell-mediated allergic response was studied with the possible mechanisms of action, focusing on the histamine release and pro-inflammatory cytokine secretion in mast cells. Sitagliptin produced dose dependent inhibition in compound 48/80-induced systemic reactions. In addition, sitagliptin attenuated IgE-mediated skin allergic reaction. Sitagliptin dose-dependently reduced compound 48/80- and IgE-induced histamine release from mast cells. Sitagliptin decreased the secretion of pro-inflammatory cytokines, tumor necrosis factor-α, in mast cells. So, the finding of this study provides evidence that sitagliptin inhibits mast cell derived allergic reactions, and involvement of pro-inflammatory cytokine secretion in such effects.

Sitagliptin enhances the neuroprotective effect of pregabalin against pentylenetetrazole-induced acute epileptogenesis in mice: Implication of oxidative, inflammatory, apoptotic and autophagy pathways

ABSTRACT The current investigation aimed at studying the anti‐epileptogenic effect of sitagliptin. The possible effect of the drug in combination with pregabalin in pentylenetetrazole (PTZ)‐ induced seizures was studied. In addition, the postulated mechanisms that could mediate such effect were explored namely, suppression of oxidative stress and neuro‐inflammatory markers, autophagy and apoptosis. Seven days prior to PTZ (60 mg/kg, sc) injection, mice were treated with sitagliptin (5, 15, and 60 mg/kg, twice daily, orally) or pregabalin (30 mg/kg, once daily, orally) or their combination. At the end of the experiment, several parameters were assessed including: oxidative/nitro‐oxidative stress such as superoxide dismutase (SOD), reduced glutathione (GSH), glutathione peroxidase (GP‐x) catalase (CAT), and lipid peroxidation assessed as malondialdehyde (MDA), nitrate/nitrite (NOx), 3‐nitrotyrosine (3‐NT). Seizure latency was evaluated. Neuronal damage was also assessed by performing tissue staining by hematoxylin and eosin, estimating hippocampus level of glutamate, gamma‐aminobutyric acid (GABA), glial fibrillary acidic protein (GFAP) and brain‐derived neurotrophic factor (BDNF). Also, markers for inflammation, autophagy and apoptosis were measured, nuclear factor erythroid‐derived 2‐ like 2 (Nrf2), nuclear factor kappa‐B (NF‐&kgr;B), phosphatidylethanolamine‐conjugated form of microtubule‐associated protein light chain‐3 (LC3‐II), casapase‐3, Bcl‐2‐like protein 4 (BAX) and glucagon like peptide‐1 (GLP‐1) activity. Sitagliptin significantly suppressed epileptogenesis in PTZ‐induced seizures. Sitagliptin counteracted neuronal damage and all biochemical, and histo‐chemical alteration induced by PTZ. Also, a more significant protective effect was observed after combination with pregabalin. This study is indicative for the antiepileptogenic potential of sitagliptin with or without pregabalin in the PTZ model of epilepsy which is likely to be through its effect on antioxidant, anti‐apoptotic and autophagic pathways. HighlightsSitagliptin protected against PTZ‐induced seizures.Sitagliptin enhanced the antiepileptic action of pregabalin.Sitagliptin acted via antioxidative, GLP1, autophagy, antiapoptotic & anti‐inflammatory.

Chinese Propolis Attenuates In-Vivo and In-Vitro Asthmatic Reactions

This study was designed to evaluate the inhibitory effects of Chinese Propolis (prepared as an ethanolic extract) on asthmatic reactions in-vivo and in-vitro. Ethanolic extract of propolis (EEP) significantly inhibited OVA-induced contractions of passively sensitized guinea pig tracheal zigzag preparations producing significant increase and decrease in EC50 and Emax, respectively. EEP appeared to exhibit significant inhibitory effects on allergic and inflammatory reaction associated murine model of asthma. EEP significantly reduced aggregation of inflammatory cells in bronchoalveolar lavage (BAL) fluid and in lung tissues with marked dilated bronchia. Also, EEP markedly reduced serum IgE and lung mRNA levels of inducible nitric oxide synthase (iNOS), transforming growth factor-β1 (TGF-β1) and tumour necrosis factor-α (TNF-α) in mice. These results suggest that EEP is a potent inhibitor of the inflammatory changes associating asthma and it could be used as an adjuvant therapy for patients with allergic airway inflammation.

Influence of alpha-lipoic acid on nicotine-induced lung and liver damage in experimental rats

Nicotine mediates some of the injurious effects caused by consuming tobacco products. This work aimed at investigating the defensive role of alpha-lipoic acid (ALA) with its known antioxidant and antiinflammatory effect in nicotine-induced lung and liver damage. Rats were arranged into 4 groups: control, nicotine, ALA, and ALA-nicotine groups. Oxidative stress and antioxidant status were determined by assessing thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), and glutathione (GSH) levels in lung and liver. Liver enzymes and lipid profiles were measured and pulmonary and hepatic damage were assessed by histopathological examination. Also, serum levels of transforming growth factor beta 1 (TGF-β1) and vascular cell adhesion molecule 1 (VCAM-1) were determined. The results revealed an increase in TBARS in tissues and a reduction in both SOD and GSH activity in the nicotine-treated rats. Nicotine induced high levels of liver enzymes, TGF-β1, VCAM-1, and dyslipidemia with histopathological changes in the lung and liver. ALA administration along with nicotine attenuated oxidative stress and normalized the SOD and GSH levels, ameliorated dyslipidemia, and improved TGF-β1 and VCAM-1 with better histopathology of the lung and liver. The study data revealed that ALA may be beneficial in alleviating nicotine-induced oxidative stress, dyslipidemia, and both lung and liver damage.

Ameliorative effect of trimetazidine on cisplatin-induced hepatotoxicity in rats

This study was designed to evaluate the protective effects of trimetazidine (TMZ) against cisplatin (CP) induced liver damage in rats. Animals were distributed among 4 groups as follows: control group; TMZ group (20 mg/kg body mass, per oral), which was treated for 10 days; CP group (6 mg/kg, by intraperitoneal injection), which received a single injection; and the CP + TMZ group (20 mg/kg, per oral), which received TMZ 4 days before and 6 days after CP injection. The extent of hepatic damage was studied by assessing biochemical parameters and histopathological evaluation of the extracted liver tissue. The results revealed that liver enzymes were markedly elevated after injection of CP, as evident from significant increases in the serum levels of alanine transaminase (AST), alanine aminotransferase (ALT), gamma glutamyl transferase (γ-GT), and lactate dehydrogenase (LDH), as well as marked changes to the liver architecture, with a significant decrease in serum levels of albumin. There were also marked changes to the antioxidant defense system, as indicated by significant decreases in total antioxidants and hepatic levels of reduced glutathione (GSH) and superoxide dismutase (SOD), together with a significant increase in lipid peroxidation. However, there was a significant increase in the activity of hepatic nuclear factor kappa B (NF-κB) as well as hepatic Bax protein expression. We conclude that TMZ protects against CP-induced liver damage through scavenging free radicals and anti-inflammatory and antiapoptotic effects, as well as through reducing NF-κB activation.

The protective effect of vildagliptin in chronic experimental cyclosporine A-induced hepatotoxicity

The study examined the effect of dipeptidyl peptidase-4 (DPP-4) inhibitor, vildagliptin, in cyclosporine (CsA)-induced hepatotoxicity. Rats were divided into 4 groups treated for 28 days: control (vehicle), vildagliptin (10 mg/kg, orally), CsA (20 mg/kg, s.c.), and CsA-vildagliptin group. Liver function was assessed by measuring serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma glutamyltransferase (γGT), lactate dehydrogenase (LDH), and albumin, and histopathological changes of liver were examined. Oxidative stress markers were evaluated. Assessment of nuclear factor-kappa B (NF-κB) activity in hepatic nuclear extract, serum DPP-4, and expression of Bax and Bcl2 were also done. CsA-induced hepatotoxicity was evidenced by increase in serum levels of AST, ALT, and γGT; a decrease in serum albumin; and a significant alteration in hepatic architecture. Also, significant increase in thiobarbituric acid reactive substance (TBARS) and decrease in superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione (GSH) levels, increased expression Bax proteins with deceased expression of Bcl2, and increased hepatic activity of NF-κB and serum DPP-4 level were observed upon CsA treatment. Vildagliptin significantly improved all altered parameters induced by CsA administration. Vildagliptin has the potential to protect the liver against CsA-induced hepatotoxicity by reducing oxidative stress, DPP-4 activity, apoptosis, and inflammation.