Tumor necrosis factor ? decreases nitric oxide synthase type 3 expression primarily via Rho/Rho kinase in the thick ascending limb.

ABSTRACT: Inappropriate Na(+) reabsorption by thick ascending limbs (THALs) induces hypertension. NO produced by NO synthase type 3 (NOS3) inhibits NaCl reabsorption by THALs. Tumor necrosis factor ? (TNF-?) decreases NOS3 expression in endothelial cells and contributes to increases in blood pressure. However, the effects of TNF-? on THAL NOS3 and the signaling cascade are unknown. TNF-? activates several signaling pathways, including Rho/Rho kinase (ROCK), which is known to reduce NOS3 expression in endothelial cells. Therefore, we hypothesized that TNF-? decreases NOS3 expression via Rho/ROCK in rat THAL primary cultures. THAL cells were incubated with either vehicle or 1 nmol/L of TNF-? for 24 hours, and NOS3 expression was measured by Western blot. TNF-? decreased NOS3 expression by 51 ± 6% (P<0.002) and blunted stimulus-induced NO production. A 10-minute treatment with TNF-? stimulated RhoA activity by 60 ± 23% (P<0.04). Inhibition of Rho GTPase with 0.05 ?g/mL of C3 exoenzyme blocked TNF-?-induced reductions in NOS3 expression by 30 ± 8% (P<0.02). Inhibition of ROCK with 10 ?mol/L of H-1152 blocked TNF-?-induced decreases in NOS3 expression by 66 ± 15% (P<0.001). Simultaneous inhibition of Rho and ROCK had no additive effect. Myosin light chain kinase, NO, protein kinase C, mitogen-activated kinase kinase, c-Jun amino terminal kinases, and Rac-1 were also not involved in TNF-?-induced decreases in NOS3 expression. We conclude that TNF-? decreases NOS3 expression primarily via Rho/ROCK in rat THALs. These data suggest that some of the beneficial effects of ROCK inhibitors in hypertension could be attributed to the mitigation of TNF-?-induced reduction in NOS3 expression.

SUBMITTER: Ramseyer VD 

PROVIDER: S-EPMC3760512 | biostudies-literature | 2012 Jun

REPOSITORIES: biostudies-literature