Pirooz Eslami

Uric acid stimulates vascular smooth muscle cell proliferation and oxidative stress via the vascular renin-angiotensin system.

Background Plasma uric acid has been associated with hypertension in a variety of disorders, and has been shown to be predictive of hypertension. The mechanistic role of uric acid in the development of hypertension is not known however. Method We tested the hypothesis that uric acid stimulates vascular smooth muscle cell (VSMC) proliferation and oxidative stress by stimulating the vascular renin–angiotensin system (RAS). Rat VSMC were exposed to 0–300 μmol uric acid for 48 h. Results Uric acid (200 and 300 μmol) stimulated the proliferation of VSMC as measured by thymidine uptake. This effect was prevented by 10−6 mol losartan or by 10−6 mol captopril. Incubation of VSMC with uric acid for 48 h also increased angiotensinogen messenger RNA expression and intracellular concentrations of angiotensin II. These responses were also inhibited by losartan and captopril. Increased expression of angiotensinogen mRNA was also inhibited by co-incubation with PD 98059, a mitogen-activated protein (MAP) kinase inhibitor. Uric acid stimulated the production of hydrogen peroxide and 8-isoprostane in VSMC. These increases in oxidative stress indicators were significantly reduced by co-incubating the cells with captopril or losartan. Uric acid also decreased nitrite and nitrate concentrations in the culture medium, an effect that was prevented by losartan and captopril. Conclusion These results demonstrate that uric acid stimulates proliferation, angiotensin II production, and oxidative stress in VSMC through tissue RAS. This suggests that uric acid causes cardiovascular disorders by stimulating the vascular RAS, and this stimulation may be mediated by the MAP kinase pathway.

Vascular Angiotensin type 1 receptor expression is associated with vascular dysfunction, oxidative stress and inflammation in fructose-fed rats.

This study determined whether or not oxidative stress and vascular dysfunction in fructose-induced hyperinsulinemic rats are associated with activation of the vascular renin-angiotensin system (RAS). Four groups of rats were used. CONT rats were fed normal rat chow, CONT+CAP were fed normal rat chow and given 500 mg/L captopril in their drinking water, fructose-fed rats (FFR) were fed a high-fructose diet and FFR+CAP were fed the high-fructose diet plus captopril in water. After 8 weeks, the vascular reactivity of mesenteric artery segments was measured. Blood was analyzed for insulin, glucose, hydrogen peroxide and 8-isoprostane. Aortic and heart tissue were used for subjected to quantitative reverse transcription–polymerase chain reaction (qRT-PCR) analysis. Systolic blood pressure was significantly higher in FFR (p<0.05), and captopril treatment inhibited the blood pressure increase. Mesenteric artery dose-response curves to acetylcholine were shifted to the right in FFR (p<0.05) and were normal in FFR+CAP. Plasma insulin (p<0.05), hydrogen peroxide (p<0.02) and 8-isoprostane (p<0.05) were increased in FFR. Captopril treatment reducd hydrogen peroxide and 8-isoprostane concentrations. Aortic tissue mRNA expression levels were increased for angiotensin-converting enzyme (ACE, p<0.05), angiotensin type 1 receptor (AT1R, p<0.02), NOX4 (p<0.02) and VCAM-1 (p<0.05) in FFR aortic samples. Captopril treatment reduced AT1R, NOX4 and VCAM-1 expression in FFR to levels not different from CONT. Similar changes in heart tissue mRNA expression for angiotensinogen, AT1R and NOX4 were also observed. These results demonstrate that vascular RAS is upregulated in FFR and support the hypothesis that vascular RAS mediates vascular dysfunction and vascular oxidative stress in FFR.

Early intervention with a small molecule inhibitor for tumor nefosis factor-α prevents cognitive deficits in a triple transgenic mouse model of Alzheimer’s disease

BackgroundChronic neuroinflammation is an important component of Alzheimer’s disease and could contribute to neuronal dysfunction, injury and loss that lead to disease progression. Multiple clinical studies implicate tumor necrosis factor-α as an inflammatory mediator of neurodegeneration in patients with Alzheimer’s because of elevated levels of this cytokine in the cerebrospinal fluid, hippocampus and cortex. Current Alzheimer’s disease interventions are symptomatic treatments with limited efficacy that do not address etiology. Thus, a critical need exists for novel treatments directed towards modifying the pathophysiology and progression.MethodsTo investigate the effect of early immune modulation on neuroinflammation and cognitive outcome, we treated triple transgenic Alzheimer’s disease mice (harboring PS1M146V, APPSwe, and tauP301L transgenes) with the small molecule tumor necrosis factor-α inhibitors, 3,6′-dithiothalidomide and thalidomide, beginning at four months of age. At this young age, mice do not exhibit plaque or tau pathology but do show mild intraneuronal amyloid beta protein staining and a robust increase in tumor necrosis factor-α. After 10 weeks of treatment, cognitive performance was assessed using radial arm maze and neuroinflammation was assessed using biochemical, stereological and flow cytometric endpoints.Results3,6′-dithiothalidomide reduced tumor necrosis factor-α mRNA and protein levels in the brain and improved working memory performance and the ratio of resting to reactive microglia in the hippocampus of triple transgenic mice.In comparison to non-transgenic controls, triple transgenic Alzheimer’s disease mice had increased total numbers of infiltrating peripheral monomyelocytic/granulocytic leukocytes with enhanced intracytoplasmic tumor necrosis factor-α, which was reduced after treatment with 3,6′-dithiothalidomide.ConclusionsThese results suggest that modulation of tumor necrosis factor-α with small molecule inhibitors is safe and effective with potential for the long-term prevention and treatment of Alzheimer’s disease.

Insulin stimulates endogenous angiotensin II production via a mitogen-activated protein kinase pathway in vascular smooth muscle cells

Objective The present study was designed to determine the effects of insulin on cytosolic angiotensin II production and proliferation in cultured rat vascular smooth muscle cells. Design and methods Vascular smooth muscle cells were incubated with insulin for 48 h. Cytosolic angiotensin I and II were determined by radioimmunoassays of purified cell homogenates. Angiotensin II was also detected by immunohistochemistry of intact cells. Cell proliferation was determined by pulse labeling with radiolabeled thymidine. Angiotensinogen mRNA expression was determined by slot-blot analysis. Results Insulin significantly increased cytosolic angiotensin II concentration in vascular smooth muscle cells. Lisinopril, omapatrilat and irbesartan inhibited this increase of angiotensin II, but had no effect on angiotensin I levels. Immunohistochemical staining confirmed the presence of angiotensin II in control and insulin-treated vascular smooth muscle cells. Insulin increased cell proliferation, and addition of lisinopril, omapatrilat or irbesartan inhibited this effect. Insulin also increased expression of angiotensinogen mRNA in cultured vascular smooth muscle cells, but PD98059, a mitogen-activated protein kinase inhibitor, prevented the rise in angiotensinogen expression. Conclusion These results support the concept that insulin stimulates angiotensin II production in cultured vascular smooth muscle cells through a mitogen-activated, protein kinase-dependent pathway that might be a factor in the progression of atherosclerosis. Agents that block the renin–angiotensin system have direct protective effects, reducing vascular angiotensin II and growth of vascular smooth muscle cells and are thus of cardiovascular benefit.

A derivative of the brain metabolite lanthionine ketimine improves cognition and diminishes pathology in the 3 × Tg-AD mouse model of Alzheimer disease.

Lanthionine ketimine ([LK] 3,4-dihydro-2H-1,4-thiazine-3,5-dicarboxylic acid) is the archetype for a family of naturally occurring brain sulfur amino acid metabolites, the physiologic function of which is unknown. Lanthionine ketimine and its synthetic derivatives have recently demonstrated neurotrophic, neuroprotective, and antineuroinflammatory properties in vitro through a proposed mechanism involving the microtubule-associated protein collapsin response mediator protein 2. Therefore, studies were undertaken to test the effects of a bioavailable LK ester in the 3 × Tg-AD mouse model of Alzheimer disease. Lanthionine ketimine ester treatment substantially diminished cognitive decline and brain amyloid-β (Aβ) peptide deposition and phospho-Tau accumulation in 3 × Tg-AD mice and also reduced the density of Iba1-positive microglia. Furthermore, LK ester treatment altered collapsin response mediator protein 2 phosphorylation. These findings suggest that LK may not be a metabolic waste but rather a purposeful neurochemical, the synthetic derivatives of which constitute a new class of experimental therapeutics for Alzheimer disease and related entities.

Oral TNFα Modulation Alters Neutrophil Infiltration, Improves Cognition and Diminishes Tau and Amyloid Pathology in the 3xTgAD Mouse Model.

Cytokines such as TNFα can polarize microglia/macrophages into different neuroinflammatory types. Skewing of the phenotype towards a cytotoxic state is thought to impair phagocytosis and has been described in Alzheimer’s Disease (AD). Neuroinflammation can be perpetuated by a cycle of increasing cytokine production and maintenance of a polarized activation state that contributes to AD progression. In this study, 3xTgAD mice, age 6 months, were treated orally with 3 doses of the TNFα modulating compound isoindolin-1,3 dithione (IDT) for 10 months. We demonstrate that IDT is a TNFα modulating compound both in vitro and in vivo. Following long-term IDT administration, mice were assessed for learning & memory and tissue and serum were collected for analysis. Results demonstrate that IDT is safe for long-term treatment and significantly improves learning and memory in the 3xTgAD mouse model. IDT significantly reduced paired helical filament tau and fibrillar amyloid accumulation. Flow cytometry of brain cell populations revealed that IDT increased the infiltrating neutrophil population while reducing TNFα expression in this population. IDT is a safe and effective TNFα and innate immune system modulator. Thus small molecule, orally bioavailable modulators are promising therapeutics for Alzheimer’s disease.