Lack of cyclophilin D protects against the development of acute lung injury in endotoxemia.

Sepsis caused by LPS is characterized by an intense systemic inflammatory response affecting the lungs, causing acute lung injury (ALI). Dysfunction of mitochondria and the role of reactive oxygen (ROS) and nitrogen species produced by mitochondria have already been proposed in the pathogenesis of sepsis; however, the exact molecular mechanism is poorly understood. Oxidative stress induces cyclophilin D (CypD)-dependent mitochondrial permeability transition (mPT), leading to organ failure in sepsis. In previous studies mPT was inhibited by cyclosporine A which, beside CypD, inhibits cyclophilin A, B, C and calcineurin, regulating cell death and inflammatory pathways. The immunomodulatory side effects of cyclosporine A make it unfavorable in inflammatory model systems. To avoid these uncertainties in the molecular mechanism, we studied endotoxemia-induced ALI in CypD(-/-) mice providing unambiguous data for the pathological role of CypD-dependent mPT in ALI. Our key finding is that the loss of this essential protein improves survival rate and it can intensely ameliorate endotoxin-induced lung injury through attenuated proinflammatory cytokine release, down-regulation of redox sensitive cellular pathways such as MAPKs, Akt, and NF-κB and reducing the production of ROS. Functional inhibition of NF-κB was confirmed by decreased expression of NF-κB-mediated proinflammatory genes. We demonstrated that impaired mPT due to the lack of CypD reduces the severity of endotoxemia-induced lung injury suggesting that CypD specific inhibitors might have a great therapeutic potential in sepsis-induced organ failure. Our data highlight a previously unknown regulatory function of mitochondria during inflammatory response.

Suppressing LPS-induced early signal transduction in macrophages by a polyphenol degradation product: a critical role of MKP-1.

Macrophages represent the first defense line against bacterial infection and therefore, play a crucial role in early inflammatory response. In this study, we investigated the role of MAPKs and MKP-1 activation in regulation of an early inflammatory response in RAW 264.7 macrophage cells. We induced the inflammatory response by treating the macrophages with LPS and inhibited an early inflammatory response by using ferulaldehyde, a water-soluble end-product of dietary polyphenol degradation that we found previously to exert its beneficial anti-inflammatory effects during the early phase of in vivo inflammation. We found that LPS-induced ROS and nitrogen species formations were reduced by ferulaldehyde in a concentration-dependent manner, and ferulaldehyde protected mitochondria against LPS-induced rapid and massive membrane depolarization. LPS induced early suppression of MKP-1, which was accompanied by activation of JNK, ERK, and p38 MAPK. By reversing LPS-induced early suppression of MKP-1, ferulaldehyde diminished MAPK activation, thereby inhibiting NF-κB activation, mitochondrial depolarization, and ROS production. Taken together, our data suggest that ferulaldehyde exerts its early anti-inflammatory effect by preserving the mitochondrial membrane integrity and shifting the expression of MKP-1 forward in time in macrophages.