Initiation of acute phase response and synthesis of cytokines

Abstract

A variety of injuries, such as bacterial infection or ischemic tissue necrosis, induce systemic acute phase reaction expressed as fever, leukocytosis, release of several hormones, activation of clotting, complement and kinin forming pathways, and drastic increase of synthesis of certain plasma proteins. The reaction is triggered by 'alarm molecules', including free radicals, which activate several stress-sensitive protein kinases (ERK, p38, JNK) in macrophages and other responsive cells. These kinases phosphorylate, usually in a multi-step cascade, transcription factors belonging primarily to C/EBP, NF-kappa B and AP-1 families. Active transcription factors after translocation to nucleus interact with responsive elements in the gene promoters of acute-phase cytokines: tumor necrosis factor-alpha, interleukin-1 and interleukin-6. Enhanced transcription of these genes is usually followed by rapid translation and precursor protein processing leading to the release of biologically active cytokines. Fine tuning of the acute phase response appears to be regulated at all stages: primary signals, kinase cascades, transcription factors, mRNA stability and translation, cytokine precursor processing, secretion and bioavailability. This makes possible designing of specific inhibitors of cytokine synthesis as potential therapeutic drugs.