MLN4924, A Neddylation Inhibitor, Improves the Vascular Reactivity but Causes Early Mortality in Polymicrobial Sepsis: Effect on Vascular RhoA/ROCK Signaling.

Vascular hyporeactivity is one of the the leading causes of death in sepsis. Ubiquitylation regulates the turnover of different cellular proteins; however, its role in controlling vascular dysfunction in sepsis is largely unknown. Herein, we aimed to evaluate the role of Cullin-3-RING ubiquitin ligase in regulating vascular contractile protein (RhoA) homeostasis and thereby regulating sepsis-induced vascular dysfunction. Sepsis was induced by caecal ligation and puncture (CLP) in mice. Cullin neddylation inhibitor (MLN4924) was evaluated for its possible therapeutic use in experimental sepsis in mice. Sepsis significantly impaired vascular RhoA/ROCK signaling as corroborated by marked increase in vasorelaxant response to Y-27632 (a Rho kinase inhibitor) which was found to be mediated by iNOS/NO/sGC pathway. Further, a significant down-expression of vascular RhoA/ROCK in septic mice was accompanied with increase in the protein expression of neddylated cullin3. Additionally, the silencing of cullin3 in vascular smooth muscle cells resulted in increase in the protein expression of RhoA. Treatment of septic mice with MLN4924, a neddylation inhibitor, significantly improved the vascular reactivity as evidenced by reduction in relaxant response to Y-27632, increase in protein level of RhoA in aorta with concomitant restoration of the contractile response to nor-adrenaline. However, MLN4924 treated mice showed higher bacterial load in blood, peritoneal lavage, lungs and spleen of septic mice. Taken together, sepsis-induced increase in cullin3 mediated degradation of RhoA possibly contributes to the vascular hyporeactivity. Thus, inhibition of vasculo-specific cullin neddylation by MLN4924 seems a potential therapeutic target for treating sepsis-induced vascular dysfunctions.