Inflammasome mRNA expression in human monocytes during early septic shock

Abstract

Rationale: 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.

Objectives: 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.

Methods: 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.

Measurements and main results: 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).

Conclusions: 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.

Figure 1.

NALP1 (NACHT, leucine-rich repeat and pyrin domain containing 1) and hospital survival. Plot of NALP1 mRNA levels from monocytes of normal subjects (open circles; n = 22), critically ill control subjects (open squares; n = 20), and patients with septic shock who survived to hospital discharge (half-closed squares; n = 11) or died in hospital (closed squares; n = 15). Monocytes were collected within 24 hours of septic shock and subjected to quantitative polymerase chain reaction. Individual points and medians are shown. Post hoc P values for pairwise comparisons based on Wilcoxon test demonstrated that there was no statistical difference between the normal subjects, the critically ill control subjects, and sepsis survivors; however, the NALP1 levels for sepsis nonsurvivors was less than for sepsis survivors (P = 0.0064).