Noha N. Nassar

Telmisartan Attenuates Colon Inflammation, Oxidative Perturbations and Apoptosis in a Rat Model of Experimental Inflammatory Bowel Disease

Accumulating evidence has indicated the implication of angiotensin II in the pathogenesis of inflammatory bowel diseases (IBD) via its proinflammatory features. Telmisartan (TLM) is an angiotensin II receptor antagonist with marked anti-inflammatory and antioxidant actions that mediated its cardio-, reno- and hepatoprotective actions. However, its impact on IBD has not been previously explored. Thus, we aimed to investigate the potential alleviating effects of TLM in tri-nitrobenezene sulphonic acid (TNBS)-induced colitis in rats. Pretreatment with TLM (10 mg/kg p.o.) attenuated the severity of colitis as evidenced by decrease of disease activity index (DAI), colon weight/length ratio, macroscopic damage, histopathological findings and leukocyte migration. TLM suppressed the inflammatory response via attenuation of tumor necrosis factor-α (TNF-α), prostaglandin E2 (PGE2) and myeloperoxidase (MPO) activity as a marker of neutrophil infiltration besides restoration of interleukin-10 (IL-10). TLM also suppressed mRNA and protein expression of nuclear factor kappa B (NF-κB) p65 and mRNA of cyclo-oxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) proinflammatory genes with concomitant upregulation of PPAR-γ. The alleviation of TLM to colon injury was also associated with inhibition of oxidative stress as evidenced by suppression of lipid peroxides and nitric oxide (NO) besides boosting glutathione (GSH), total anti-oxidant capacity (TAC) and the activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx). With respect to apoptosis, TLM downregulated the increased mRNA, protein expression and activity of caspase-3. It also suppressed the elevation of cytochrome c and Bax mRNA besides the upregulation of Bcl-2. Together, these findings highlight evidences for the beneficial effects of TLM in IBD which are mediated through modulation of colonic inflammation, oxidative stress and apoptosis.

Glibenclamide ameliorates ischemia-reperfusion injury via modulating oxidative stress and inflammatory mediators in the rat hippocampus.

Stroke remains a debilitating disease with high incidence of morbidity and mortality, where many reports provide promising venues for prevention/treatment of such ailment. Glibenclamide, a selective blocker of KATP channels, was reported to protect against ischemia and ischemia-reperfusion (IR) injury in several experimental models. Hence, the present study aimed to investigate the possible involvement of free radicals as well as inflammatory and anti-inflammatory mediators in the hippocampus of rats exposed to IR. To this end, male Wistar rats were divided into 3 groups: group I served as sham operated controls; group II was subjected to 15 min ischemia by occlusion of both common carotid arteries, followed by 60 min reperfusion; group III was injected with glibenclamide (1mg/kg, i.p.) 10 min before ischemic-reperfusion injury. IR increased lipid peroxides, myeloperoxidase activity, TNF-α and PGE(2), while decreasing glutathione, total antioxidant capacity, nitric oxide and IL-10 levels in the hippocampus. Glibenclamide reversed all the former alterations, thus highlighting a potential therapeutic utility for this sulphonyl urea in IR brain injury via modulating oxidative stress and inflammatory mediators.

Cerebrolysin Ameloriates Cognitive Deficits in Type III Diabetic Rats

Cerebrolysin (CBL), a mixture of several active peptide fragments and neurotrophic factors including brain-derived neurotrophic factor (BDNF), is currently used in the management of cognitive alterations in patients with dementia. Since Cognitive decline as well as increased dementia are strongly associated with diabetes and previous studies addressed the protective effect of BDNF in metabolic syndrome and type 2 diabetes; hence this work aimed to evaluate the potential neuroprotective effect of CBL in modulating the complications of hyperglycaemia experimentally induced by streptozotocin (STZ) on the rat brain hippocampus. To this end, male adult Sprague Dawley rats were divided into (i) vehicle- (ii) CBL- and (iii) STZ diabetic-control as well as (iv) STZ+CBL groups. Diabetes was confirmed by hyperglycemia and elevated glycated haemoglobin (HbA1c%), which were associated by weight loss, elevated tumor necrosis factor (TNF)-α and decreased insulin growth factor (IGF)-1β in the serum. Uncontrolled hyperglycemia caused learning and memory impairments that corroborated degenerative changes, neuronal loss and expression of caspase (Casp)-3 in the hippocampal area of STZ-diabetic rats. Behavioral deficits were associated by decreased hippocampal glutamate (GLU), glycine, serotonin (5-HT) and dopamine. Moreover, diabetic rats showed an increase in hippocampal nitric oxide and thiobarbituric acid reactive substances versus decreased non-protein sulfhydryls. Though CBL did not affect STZ-induced hyperglycemia, it partly improved body weight as well as HbA1c%. Such effects were associated by enhancement in both learning and memory as well as apparent normal cellularity in CA1and CA3 areas and reduced Casp-3 expression. CBL improved serum TNF-α and IGF-1β, GLU and 5-HT as well as hampering oxidative biomarkers. In conclusion, CBL possesses neuroprotection against diabetes-associated cerebral neurodegeneration and cognitive decline via anti-inflammatory, antioxidant and antiapototic effects.

Saxagliptin: a novel antiparkinsonian approach.

The emergence of glucagon-like peptide-1 as a crucial contender in modifying neurodegenerative diseases in the preclinical studies has instigated interest in investigating the antiparkinsonian effect of dipeptidyl peptidase (DPP)-4 inhibition. Notably, saxagliptin (SAX), the DPP-4 inhibitor, recently showed efficacy in ameliorating streptozotocin-induced Alzheimers disease; however, its effect on Parkinsons disease (PD) has not yet been elucidated. In a rat rotenone (ROT) model, SAX prominently improved motor performance as well as muscle coordination and corrected akinesia. Moreover, SAX preserved substantia nigra pars compacta tyrosine hydroxylase (TH) immunoreactivity while halting the reduction in the striatal TH, dopamine (DA) and complex I. Meanwhile, SAX prevented the ROT-induced increment of striatal DPP-4 and the decline in cAMP, ATP/ADP and brain-derived neurotropic factor levels. Improvement in striatal energy level was associated with partial hindrance of ROT-induced body weight reduction. In addition, through its anti-inflammatory potential, SAX decreased the ROT-induced nuclear factor-κΒ, inducible nitric oxide synthase, tumor necrosis factor-α, intracellular adhesion molecule-1 and myeloperoxidase. The antiapoptotic marker B-cell lymphoma-2 was enhanced by SAX, versus reduction in caspase-3 and its intrinsic apoptotic activator cytochrome C. Furthermore, SAX amended alterations induced by ROT in the thiobarbituric acid reactive substances and the transcriptional factor Nrf-2 level. In conclusion, SAX can be introduced as a novel approach for the management of PD based on the remarkable improvement in motor functions denoting antiparkinsonian efficacy via antioxidant, anti-inflammatory, antiapoptotic, neuroprotective and neurorestorative mechanisms. These effects were linked to DPP-4 inhibition, reduced neurodegeneration and enhanced DA synthesis.

Brainstem Phosphorylated Extracellular Signal-Regulated Kinase 1/2-Nitric-Oxide Synthase Signaling Mediates the Adenosine A2A-Dependent Hypotensive Action of Clonidine in Conscious Aortic Barodenervated Rats

The cellular mechanisms that underlie the enhancement of clonidine-evoked hypotension in aortic barodenervated (ABD) rats and its dependence on central adenosine A2A receptor (A2AR) are not known. We tested the hypothesis that A2AR-mediated phosphorylation of extracellular signal-regulated kinase (pERK)1/2 in the rostral ventrolateral medulla (RVLM) and its downstream activation of nitric-oxide synthase (NOS)-NO signaling underlie the centrally (clonidine)-mediated hypotension. We first demonstrated an up-regulation of the molecular targets for clonidine [imidazoline I1 and α2A adrenergic receptors (α2AR)] in the RVLM of ABD compared with sham-operated (SO) rats; this finding might explain the enhanced clonidine hypotension in ABD rats. A similar anatomical up-regulation of the RVLM A2AR was evident and was complemented with enhanced central A2AR [2-[4-[(2-carboxyethyl)phenyl]ethylamino]-5′-N-ethylcarboxamidoadenosine; CGS21680]-mediated hypotension in ABD rats. The hypotension produced by intracisternal CGS21680 or clonidine, in conscious ABD rats, was associated with a significant increase in pERK1/2 level in the RVLM. Whereas selective A2AR blockade [5-amino-7-(2-phenylethyl)-2-(2-furyl)-pyrazolo[4,3-ϵ]-1,2,4-triazolo[1,5-c]pyrimidine; SCH58261] or NOS inhibition (Nω-nitro-l-arginine methyl ester) virtually abolished clonidine-evoked hypotension, clonidine-evoked enhancement of RVLM pERK1/2 production was only abrogated by SCH58261 pretreatment. These findings suggest that interventions that act centrally to increase RVLM neuronal pERK1/2 production elicit hypotension via the activation of downstream NOS-NO signaling. The findings also yield insight into a cellular mechanism that might explain the dependence of centrally (clonidine)-mediated hypotension on central A2AR signaling in the ABD rat.

Resveratrol reverses ET-1-evoked mitogenic effects in human coronary arterial cells by activating the kinase-G to inhibit ERK-enzymes.

In human coronary smooth muscle cells (HCSMC), treatment with the vascular mitogen; endothelin-1 (ET-1), induced cell proliferation and stimulated ERK-1/2 phosphorylation at active sites. Pretreatment with the MEK-ERK inhibitor (PD98059) appreciably reversed the mitogenic effects of ET-1. On the other hand, pretreatment with the polyphenolic stilbene resveratrol (RSVL, 1-100 microM) triggered more prominent inhibition of ET-1-evoked cell proliferation and ERK1/2 activation. Besides, RSVL also markedly (2-3 fold) and rapidly enhanced cGMP formation, but had no effect on cAMP levels. This RSVL-evoked upregulation of cGMP was insensitive to pretreatment with the soluble guanylyl cyclase (sGC)-inhibitor (ODQ, 10 microM), but was ablated with an inhibitor of pGC (PMA, 0.1 microM). Further, pretreatment with the specific cGMP-phosphodiesterase inhibitor, zaprinast (10 microM) appreciably augmented RSVL-evoked cGMP formation, ERK inhibition, and cytostatic response. Moreover, the RSVL-induced ERK-inhibitory effects were significantly reversed by the kinase-G inhibitor, KT-5823 (10 microM; 69%), but not by the kinase-A inhibitor (KT-5720). These results demonstrate a novel signaling pathway for RSVL that leads from activation of the pGC/kinase-G system to inhibition of ERK1/2 and their downstream nuclear targets. This pathway functions to counteract the atherogenic signaling induced by vascular mitogens.

Central Adenosine Signaling Plays a Key Role in Centrally Mediated Hypotension in Conscious Aortic Barodenervated Rats

We tested the hypothesis that clonidine-evoked hypotension is dependent on central adenosinergic pathways. Five groups of male, conscious, aortic baroreceptor-denervated (ABD) rats received clonidine (10 μg/kg i.v.) 30 min after i.v. 1) saline, 2) theophylline (10 mg/kg), or 3) 8-(p-sulfophenyl)theophylline (8-SPT) (2.5 mg/kg) or 1 h after i.p. 4) dipyridamole (5 mg/kg) or 5) an equal volume of sesame oil. Blockade of central (theophylline) but not peripheral (8-SPT) adenosine receptors abolished clonidine hypotension. In contrast, dipyridamole substantially enhanced the bradycardic response to clonidine. In additional groups, intracisternal (i.c.) dipyridamole (150 μg) and 8-SPT (10 μg) enhanced and abolished, respectively, clonidine (0.6 μg i.c.)-evoked hypotension. Because clonidine is a mixed I1/α2 agonist, we also investigated whether adenosine signaling is linked to the I1 or the α2A receptor by administering the selective I1 (rilmenidine, 25 μg) or α2A [α-methylnorepinephrine (α-MNE), 4 μg] agonist 30 min after central adenosine receptor blockade (8-SPT; 10 μg i.c.) or artificial cerebrospinal fluid. The hypotensive response elicited by rilmenidine or α-MNE was abolished in 8-SPT-pretreated rats. To delineate the role of the adenosine A2A receptor in clonidine-evoked hypotension, i.c. clonidine (0.6 μg) was administered 30 min after central adenosine receptor A2A blockade [5-amino-7-(2-phenylethyl)-2-(2-furyl)-pyrazolo[4,3-ϵ]-1,2,4-triazolo[1,5-c]-pyrimidine (SCH58261); 150 μg i.c.]. The latter virtually abolished the hypotensive and bradycardic responses elicited by clonidine. In conclusion, central adenosine A2A signaling plays a key role in clonidine-evoked hypotension in conscious aortic barodenervated rats.

Enhanced Hemeoxygenase Activity in the Rostral Ventrolateral Medulla Mediates Exaggerated Hemin-Evoked Hypotension in the Spontaneously Hypertensive Rat

In anesthetized normotensive rats, activation of brainstem hemeoxygenase (HO) elicits sympathoinhibition and hypotension. Accordingly, we tested the hypothesis that attenuated basal or induced HO activity in the rostral ventrolateral medulla (RVLM) contributes to hypertension in the spontaneously hypertensive rat (SHR). We measured basal RVLM HO expression and catalytic activity and investigated the effects of intra-RVLM HO activation (hemin) or selective HO isoform 1 (HO-1) inhibition [zinc protoporphyrin IX (ZnPPIX)] on mean arterial pressure (MAP), heart rate, and RVLM neuronal norepinephrine (NE) level (index of sympathetic activity) in conscious SHRs and Wistar Kyoto rats. Basal RVLM HO catalytic activity (bilirubin level) and HO-1 expression were significantly higher in the SHR. These neurochemical findings were corroborated by the significantly greater decreases (hemin) and increases (ZnPPIX) in RVLM NE and MAP in the SHR. By contrast, HO-independent CO release in the RVLM (CO-releasing molecule 3) elicited similar MAP reductions in both rat strains. Furthermore, pretreatment with ZnPPIX or the selective neuronal nitric-oxide synthase (nNOS) inhibitor N-propyl-l-arginine abrogated the neurochemical (RVLM cGMP) and hypotensive responses caused by hemin. In addition to demonstrating, for the first time, higher basal RVLM HO catalytic activity and HO-1 expression in the SHR, the findings suggest: 1) the exaggerated hypotension elicited by intra-RVLM HO activation in the SHR is nNOS-dependent, and 2) in the SHR, the enhanced RVLM HO-nNOS signaling compensates for the reduced expression/activity of the downstream target, soluble guanylyl cyclase. Together, the findings suggest a protective role for the RVLM HO-nNOS pathway against further increases in MAP in the SHR.

Role of adenosine A2A receptor in cerebral ischemia reperfusion injury: Signaling to phosphorylated extracellular signal-regulated protein kinase (pERK1/2)

Following brain ischemia reperfusion (IR), the dramatic increase in adenosine activates A2AR to induce further neuronal damage. Noteworthy, A2A antagonists have proven efficacious in halting IR injury, however, the detailed downstream signaling remains elusive. To this end, the present study aimed to investigate the possible involvement of phospho-extracellular signal-regulated kinase (pERK1/2) pathway in mediating protection afforded by the central A2A blockade. Male Wistar rats (250-270 g) subjected to bilateral carotid occlusion for 45 min followed by a 24-h reperfusion period showed increased infarct size corroborating histopathological damage, memory impairment and motor incoordination as well as increased locomotor activity. Those events were mitigated by the unilateral intrahippocampal administration of the selective A2A antagonist SCH58261 via a decrease in pERK1/2 downstream from diacyl glycerol (DAG) signaling. Consequent to pERK1/2 inhibition, reduced hippocampal microglial activation, glial tumor necrosis factor-alpha (TNF-α) and brain-derived neurotropic factor (BDNF) expression, glutamate (Glu), inducible nitric oxide synthase (iNOS) and thiobarbituric acid reactive substances (TBARS) were evident in animals receiving SCH58261. Additionally, the anti-inflammatory cytokine interleukin-10 (IL-10) increased following nuclear factor (erythroid-derived 2)-like 2 (Nrf-2). Taken all together, these events suppressed apoptotic pathways via a reduction in cytochrome c (Cyt. c) as well as caspase-3 supporting a crucial role for pERK1/2 inhibition in consequent reduction of inflammatory and excitotoxic cascades as well as correction of the redox imbalance.

A novel role for SIRT-1 in L-arginine protection against STZ induced myocardial fibrosis in rats.

Background L-arginine (L-ARG) effectively protects against diabetic impediments. In addition, silent information regulator (SIRT-1) activators are emerging as a new clinical concept in treating diabetic complications. Accordingly, this study aimed at delineating a role for SIRT-1 in mediating L-ARG protection against streptozotocin (STZ) induced myocardial fibrosis. Methods Male Wistar rats were allocated into five groups; (i) normal control rats received 0.1 M sodium citrate buffer (pH 4.5); (ii) STZ at the dose of 60 mg/kg dissolved in 0.1 M sodium citrate buffer (pH 4.5); (iii) STZ + sirtinol (Stnl; specific inhibitor of SIRT-1; 2 mg/Kg, i.p.); (iv) STZ + L-ARG given in drinking water (2.25%) or (v) STZ + L-ARG + Stnl. Results L-ARG increased myocardial SIRT-1 expression as well as its protein content. The former finding was paralleled by L-ARG induced reduction in myocardial fibrotic area compared to STZ animals evidenced histopathologically. The reduction in the fibrotic area was accompanied by a decline in fibrotic markers as evident by a decrease in expression of collagen-1 along with reductions in myocardial TGF-β, fibronectin, CTGF and BNP expression together with a decrease in TGF-β and hydroxyproline contents. Moreover, L-ARG increased MMP-2 expression in addition to its protein content while decreasing expression of PAI-1. Finally, L-ARG protected against myocardial cellular death by reduction in NFκ-B mRNA as well as TNF-α level in association with decline in Casp-3 and FAS expressions andCasp-3protein content in addition to reduction of FAS positive cells. However, co-administration of L-ARG and Stnl diminished the protective effect of L-ARG against STZ induced myocardial fibrosis. Conclusion Collectively, these findings associate a role for SIRT-1 in L-ARG defense against diabetic cardiac fibrosis via equilibrating the balance between profibrotic and antifibrotic mediators.