What is the role of proinflammatory mediators in the pathophysiology of systemic inflammatory response syndrome (SIRS)?

Updated: May 07, 2018
  • Author: Lewis J Kaplan, MD, FACS, FCCM, FCCP; Chief Editor: Michael R Pinsky, MD, CM, Dr(HC), FCCP, FAPS, MCCM  more...
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Answer

The release of IL-1 and TNF-α (or the presence of endotoxin or exotoxin) leads to cleavage of the nuclear factor-kB (NF-kB) inhibitor. Once the inhibitor is removed, NF-kB is able to initiate the production of messenger ribonucleic acid (mRNA), which induces the production other proinflammatory cytokines.

IL-6, IL-8, and interferon gamma are the primary proinflammatory mediators induced by NF-kB. In vitro research suggests that glucocorticoids may function by inhibiting NF-kB. TNF-α and IL-1 have been shown to be released in large quantities within 1 hour of an insult and have both local and systemic effects. In vitro studies have shown that these 2 cytokines given individually produce no significant hemodynamic response but that they cause severe lung injury and hypotension when given together. TNF-α and IL-1 are responsible for fever and the release of stress hormones (norepinephrine, vasopressin, activation of the renin-angiotensin-aldosterone system).

Other cytokines, especially IL-6, stimulate the release of acute-phase reactants such as C-reactive protein (CRP) and procalcitonin. Of note, infection has been shown to induce a greater release of TNF-α —thus inducing a greater release of IL-6 and IL-8—than trauma does. This is suggested to be the reason higher fever is associated with infection rather than trauma.

The proinflammatory interleukins either function directly on tissue or work via secondary mediators to activate the coagulation cascade and the complement cascade and the release of nitric oxide, platelet-activating factor, prostaglandins, and leukotrienes.


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