Inflammasome mRNA expression in human monocytes during early septic shock

Monocytes are central to the initiation of the inflammatory response in sepsis, with caspase-1 activation playing a key role. Monocyte deactivation during sepsis has been linked to poor outcomes.

Given the importance of caspase-1 in the immune response, we investigated whether monocytes from patients early in septic shock demonstrate alterations in mRNAs for caspase-1-related molecules.

Patients with septic shock (n = 26; age >18 years), critically ill intensive care unit patients (n = 20), and healthy volunteers (n = 22) were enrolled in a prospective cohort study in a university intensive care unit. Demographic, biological, physiologic, and plasma cytokine measurements were obtained. Monocytes were assayed for ex vivo tumor necrosis factor-alpha production, and fresh monocyte mRNA was analyzed by quantitative reverse-transcription polymerase chain reaction for Toll-like receptors, NOD-LRR proteins, cytokines, and nuclear factor-kappaB-related genes.

Relative copy numbers for the inflammasome mRNAs for ASC, caspase-1, NALP1, and Pypaf-7 were significantly lower in patients with septic shock compared with critically ill control subjects. NALP1 mRNA levels were linked to survival in patients with sepsis (P = 0.0068) and correlated with SAPS II scores (r = -0.63).

These data suggest that monocyte deactivation occurs during the earliest stages of the systemic inflammatory response and that changes in inflammasome mRNA expression are part of this process.