Atorvastatin Improves Survival in Septic Rats: Effect on Tissue Inflammatory Pathway and on Insulin Signaling

The aim of the present study was to investigate whether the survival-improving effect of atorvastatin in sepsis is accompanied by a reduction in tissue activation of inflammatory pathways and, in parallel, an improvement in tissue insulin signaling in rats. Diffuse sepsis was induced by cecal ligation and puncture surgery (CLP) in male Wistar rats. Serum glucose and inflammatory cytokines levels were assessed 24 h after CLP. The effect of atorvastatin on survival of septic animals was investigated in parallel with insulin signaling and its modulators in liver, muscle and adipose tissue. Atorvastatin improves survival in septic rats and this improvement is accompanied by a marked improvement in insulin sensitivity, characterized by an increase in glucose disappearance rate during the insulin tolerance test. Sepsis induced an increase in the expression/activation of TLR4 and its downstream signaling JNK and IKK/NF-κB activation, and blunted insulin-induced insulin signaling in liver, muscle and adipose tissue; atorvastatin reversed all these alterations in parallel with a decrease in circulating levels of TNF-α and IL-6. In summary, this study demonstrates that atorvastatin treatment increased survival, with a significant effect upon insulin sensitivity, improving insulin signaling in peripheral tissues of rats during peritoneal-induced sepsis. The effect of atorvastatin on the suppression of the TLR-dependent inflammatory pathway may play a central role in regulation of insulin signaling and survival in sepsis insult

Anti-inflammatory effect of insulin on the IKK/I'capa'B/NF-'capa'B pathway

Orientador: Mário José Abdalla SaadDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências MédicasResumo: A infusão da insulina durante a inflamação aguda melhora os resultados clínicos, mas o exato mecanismo desse efeito benéfico da insulina ainda não foi bem compreendido. Estudos recentes mostraram que a insulina tem um efeito antiinflamatório de modo que o hormônio também exibe um efeito inibidor sobre a mediação da transcrição de NF-kB em células mononucleares. Assim, o objetivo do presente estudo foi investigar os efeitos agudos da administração de insulina regular sobre a modulação de proteínas da via IKK/IkB/NF-kB e das proteínas chave da via de sinalização da insulina em tecido hepático, muscular e adiposo, a expressão de NF-kB nesses tecidos através de ELISA, o efeito do tratamento com insulina em macrófagos extraídos do peritônio de ratos e a influência dos inibidores da PI3K e MAPK na via inflamatória. Ademais, fizemos um ensaio da proteína fosfatase PP2A usando a imunoprecipitação com anticorpos anti-IKKbeta. Para o experimento, ratos machos adultos Wistar compuseram aleatoriamente 4 grupos diferentes. Três deles foram submetidos à infusão de insulina na veia porta e, então foram estimulados em 1, 3 e 5 minutos, enquanto o outro grupo (0) não foi estimulado com insulina. Em nossos resultados, observamos um aumento da fosforilação de IR, IRS1 e Akt induzida pela insulina nos três tecidos estudados. Em paralelo, houve uma redução na fosforilação de IKK e IkB após o estimulo da insulina. A ativação de NF-kB p65 no núcleo das células mostrou a redução na fosforilação do IKK e IkB no fígado, músculo e tecido adiposo. Na cultura de macrófagos tratada com insulina, após a adição dos inibidores específicos para PI3K e MAPK, observamos um aumento na fosforilação de IKK e IkB. Nossos resultados também mostraram que após estímulo da insulina houve um aumento na atividade da proteina fosfatase PP2A associada ao IKK nos três tecidos estudados. Desta forma, podemos sugerir que insulina pode induzir uma interação entre PP2A e IKK, o que resultará em mais desfosforilação de IKK e, assim, uma inibição da atividade da proteína quinase, revelando um potencial mecanismo de ação efeito anti-inflamatório da insulinaAbstract: Insulin infusion during acute inflammation improves clinical the outcomes but the exact mechanism of this beneficial effect is unclear. Recent studies have suggested that insulin has an anti-inflammatory effect in such a way that this hormone exhibits an inhibitory effect on the mediation of transcription of NF- kB in mononuclear cells. Thus, the aim of this study was to investigate the acute effects of regular insulin administration in modulation of IKK/IkB/NF-kB pathway and insulin signaling pathway (IR, IRS1 and Akt) and the DNA binding of NF-kB p65 in liver, muscle and adipose tissue of rats and also analyze the effect of treatment with insulin on macrophages of rats and the influence of PI3K and MAPK inhibitors on pathway. And finally, we analyze a phosphatase assay by using an immunoprecipitation with anti-IKKbeta antibody and PP2A phosphatase assay. For the experiment, male adult Wistar rats were divided in 4 groups. Three of them were submitted to insulin injection in the portal vein and were stimulated for 1, 3 and 5 minutes and the other group (0) was not stimulated (saline). In our results, we observed an increase in insulin-induced phosphorylation of IR, IRS1 and Akt during insulin injection in the three tissues studied. In parallel, there was a reduction in the phosphorylation of IKK and IkB after insulin stimulation. The DNA binding of NF-kB p65 in the cell nucleus showed a reduction of the IKK and IkB phosphorylation after insulin injection in liver, muscle and adipose tissue. In macrophages culture of treated with insulin and when added the specific inhibitor for PI3K and MAPK we observed an increased on phosphorylation of IKK and IkB. Our results also showed that after insulin stimulus there was an increase in PP2A phosphatase activity associated with IKK in the three tissues studied. Thus, we can suggest that insulin might induce an interaction between PP2A and IKK, which will result in more IKK dephosphorylation and thus an inhibition of this protein kinase activity, showed a possible anti-inflammatory effect of insulinMestradoMestre em Ciência

Representative blots show the JNK phosphorylation in liver (A), muscle (B) and adipose tissue (C) of sham and septic rats (upper panels).

<p>Total protein expression of JNK (A–C, lower panels). Phosphorylation of c-jun in liver (D), muscle (E) and adipose tissue (F) of sham and septic rats. Serine 307 Phosphorylation of IRS1 in liver (G), muscle (H) and adipose tissue (I) of sham and septic rats (upper panels). Total protein expression of IRS-1 (G–I, lower panels). Data are presented as means ± S.E.M from 6–8 rats per group. *P<0.05 (Sepsis/Sal vs. all others groups); **P<0.001 (Sepsis/Sal vs. control); #P<0.05 (Sepsis/Sal vs. Sepsis/Ator). IB, immunoblot; CLT: Sham/Saline; ShT: Sham/Atorvastatin; SAL: saline; ATOR: atorvastatin.</p

To evaluate the association of TLR4 with MyD88, immunoprecipitations were performed with MyD88 antibody followed by immunoblotting with TLR4 specific antibody.

<p>Representative blots show TLR4 activation (upper panels) and expression (lower panels) in liver (A), muscle (B) and adipose tissue (C) of sham and septic rats. IKKβ phosphorylation in liver (D), muscle (E) and adipose (F) of sham and septic rats. Total protein expression of IKKβ (D–F, lower panels). Phosphorylation of IκBα in liver (G), muscle (H) and adipose (I) of sham and septic rats. Data are presented as means ±S.E.M from 6–8 rats per group. *P<0.05 (Sepsis/Sal vs. all other groups); **P<0.001 (Sepsis/Sal vs. control); #P<0.05 (Sepsis/Sal vs. Sepsis/Ator). IB, immunoblot; CLT: Sham/Saline; ShT: Sham/Atorvastatin; SAL: saline; ATOR: atorvastatin.</p

Effects of atorvastatin treatment on insulin signaling in the CLP rat.

<p>Representative blots show insulin-induced tyrosine phosphorylation of Insulin Receptor β (IRβ) in liver (A), muscle (B) and adipose (C) of sham and septic rats. Total protein expression of IRβ (A–C, lower panels). Insulin-induced tyrosine phosphorylation of Insulin Receptor Substrate 1 (IRS1) in liver (D), muscle (E) and adipose tissue (F) of sham and septic rats. Total protein expression of IRS1 (D–F, lower panels). Insulin-induced serine phosphorylation of Akt in liver (G), muscle (H) and adipose (I) of sham and septic rats. Insulin-induced threonine phosphorylation and total protein expression of Akt (G–I, lower panels). In this case, blots were stripped and reprobed with β-actin (A–I, lower panels) to confirm equal loading of proteins. Data are presented as means +/− S.E.M from 6–8 rats per group. *P<0.05 (Sepsis/Sal vs. all others groups). IB, immunoblot; CLT: Sham/Saline; ShT: Sham/Atorvastatin; SAL: saline; ATOR: atorvastatin.</p

Representative blots show the NFkB activation in nuclear fractions of liver (A), muscle (B) and adipose tissue (C) of sham and septic rats.

<p>In this case blots were stripped and reprobed with actin (A–C, lower panels) to confirm equal loading of proteins. Tissue levels of iNOS (D–F) and IL-6 (G–I) expression in liver, muscle and adipose tissue of sham and septic rats. Data are presented as means ± S.E.M from 6–8 rats per group. *P<0.05 (Sepsis/Sal vs. all others groups); **P<0.001 (Sepsis/Sal vs. control); #P<0.05 (Sepsis/Sal vs. Sepsis/Ator). IB, immunoblot; CLT: Sham/Saline; ShT: Sham/Atorvastatin; SAL: saline; ATOR: atorvastatin.</p

Effect of atorvastatin on survival in CLP sepsis model.

<p>Male Wistars rats, 8 weeks old, were given saline (Sepsis/Sal, n = 20) or atorvastatin 10 mg/kg (Sepsis/Ator, n = 20), 3 h and once a day after CLP. Survival of the rats was monitored at intervals of 12 h for 15 days. The overall difference in survival rate between the groups with and without atorvastatin was significant (P<0.0001) (A). Fasting blood glucose (B). Fasting insulin levels (C). Glucose disappearance rate (D). HOMA-IR index (E). Serum levels of TNF-α (F) and IL-6 (G). Data are presented as means and S.E. of six to eight rats per group. *P<0.05 (Sepsis saline vs. all others groups).</p