No abstract

No abstract

Abstract-Nitric oxide (NO) plays an important role in the control of vascular tone. Traditionally, its vasorelaxant activity has been attributed to the free radical form of NO (NO ⅷ ), yet the reduced form of NO (NO Ϫ ) is also produced endogenously and is a potent vasodilator of large conduit arteries. The effects of NO Ϫ in the resistance vasculature remain unknown. This study examines the activity of NO Ϫ in rat small isolated mesenteric resistance-like arteries and characterizes its mechanism(s) of action. With the use of standard myographic techniques, the vasorelaxant properties of NO ⅷ (NO gas solution), NO Ϫ (Angeli's salt), and the NO donor sodium nitroprusside were compared. Relaxation responses to Angeli's salt (pEC 50 ϭ7.51Ϯ0.13, R max ϭ95.5Ϯ1.5%) were unchanged in the presence of carboxy-PTIO (NO ⅷ scavenger) but those to NO ⅷ and sodium nitroprusside were inhibited. L-Cysteine (NO Ϫ scavenger) decreased the sensitivity to Angeli's salt (PϽ0.01) and sodium nitroprusside (PϽ0.01) but not to NO ⅷ . The soluble guanylate cyclase inhibitor ODQ (3 and 10 mol/L) concentration-dependently inhibited relaxation responses to Angeli's salt (41.0Ϯ6.0% versus control 93.4Ϯ1.9% at 10 mol/L). The voltage-dependent K ϩ channel inhibitor 4-aminopyridine (1 mmol/L) caused a 9-fold (PϽ0.01) decrease in sensitivity to Angeli's salt, whereas glibenclamide, iberiotoxin, charybdotoxin, and apamin were without effect. In combination, ODQ and 4-aminopyridine abolished the response to Angeli's salt. In conclusion, NO Ϫ functions as a potent vasodilator of resistance arteries, mediating its response independently of NO , which mediates vascular smooth muscle relaxation predominantly through the activation of soluble guanylate cyclase and subsequent accumulation of cGMP. 1 NO, however, can also exist in the oxidized state as the nitrosonium cation (NO ϩ ) and in the reduced state as the nitroxyl anion (NO Ϫ ). Little attention has been afforded to the biological activity of these alternative redox forms of NO, yet recent findings that the nitroxyl anion is produced endogenously 2,3 and displays relaxant activity within the vasculature 4,5 highlights a possible physiological role for this nitrogen oxide species. NO Ϫ can be generated directly from the enzymatic activity of NO synthase (NOS) 2,3 such that NOS-catalyzed oxidation of L-arginine results in the production of NO Ϫ , which is further oxidized to NO ⅷ by superoxide dismutase. In addition, NO Ϫ can also be formed during oxidation of the decoupled NOS product N-hydroxy-L-arginine, 6,7 from NOS in the absence of tetrahydrobiopterin, 8 after the decomposition of S-nitrosothiols 9,10 and peroxynitrite 11 and from the reduction of NO ⅷ by mitochondrial cytochrome c. 12 The biological activity of NO Ϫ can be studied by using NO Ϫ donors such as Angeli's salt. Of particular interest is the identification of NO Ϫ as a potent vasodilator, mediating relaxation of large isolated conduit arteries, 4,5,13 exerting dilator activity in the intact pulmonary vascular bed, 14 and decreas...

BACKGROUND AND PURPOSEInflammasomes are multimeric complexes that facilitate caspase-1-mediated processing of the pro-inflammatory cytokines IL-1β and IL-18. Clinical hypertension is associated with renal inflammation and elevated circulating levels of IL-1β and IL-18. Therefore, we investigated whether hypertension in mice is associated with increased expression and/or activation of the inflammasome in the kidney, and if inhibition of inflammasome activity reduces BP, markers of renal inflammation and fibrosis. EXPERIMENTAL APPROACHWild-type and inflammasome-deficient ASC −/− mice were uninephrectomized and received deoxycorticosterone acetate and saline to drink (1K/DOCA/salt). Control mice were uninephrectomized but received a placebo pellet and water. BP was measured by tail cuff; renal expression of inflammasome subunits and inflammatory markers was measured by real-time PCR and immunoblotting; macrophage and collagen accumulation was assessed by immunohistochemistry.

AimsRenal inflammation, leading to fibrosis and impaired function is a major contributor to the development of hypertension. The NLRP3 inflammasome mediates inflammation in several chronic diseases by processing the cytokines pro-interleukin (IL)-1β and pro-IL-18. In this study, we investigated whether MCC950, a recently-identified inhibitor of NLRP3 activity, reduces blood pressure (BP), renal inflammation, fibrosis and dysfunction in mice with established hypertension.Methods and resultsC57BL6/J mice were made hypertensive by uninephrectomy and treatment with deoxycorticosterone acetate (2.4 mg/day, s.c.) and 0.9% NaCl in the drinking water (1K/DOCA/salt). Normotensive controls were uninephrectomized and received normal drinking water. Ten days later, mice were treated with MCC950 (10 mg/kg/day, s.c.) or vehicle (saline, s.c.) for up to 25 days. BP was monitored by tail-cuff or radiotelemetry; renal function by biochemical analysis of 24-h urine collections; and kidney inflammation/pathology was assessed by real-time PCR for inflammatory gene expression, flow cytometry for leucocyte influx, and Picrosirius red histology for collagen. Over the 10 days post-surgery, 1K/DOCA/salt-treated mice became hypertensive, developed impaired renal function, and displayed elevated renal levels of inflammatory markers, collagen and immune cells. MCC950 treatment from day 10 attenuated 1K/DOCA/salt-induced increases in renal expression of inflammasome subunits (NLRP3, ASC, pro-caspase-1) and inflammatory/injury markers (pro-IL-18, pro-IL-1β, IL-17A, TNF-α, osteopontin, ICAM-1, VCAM-1, CCL2, vimentin), each by 25–40%. MCC950 reduced interstitial collagen and accumulation of certain leucocyte subsets in kidneys of 1K/DOCA/salt-treated mice, including CD206+ (M2-like) macrophages and interferon-gamma-producing T cells. Finally, MCC950 partially reversed 1K/DOCA/salt-induced elevations in BP, urine output, osmolality, [Na+], and albuminuria (each by 20–25%). None of the above parameters were altered by MCC950 in normotensive mice.ConclusionMCC950 was effective at reducing BP and limiting renal inflammation, fibrosis and dysfunction in mice with established hypertension. This study provides proof-of-concept that pharmacological inhibition of the NLRP3 inflammasome is a viable anti-hypertensive strategy.