Rapamycin Augments the NMDA-Mediated TNF Suppression of MRSA-Stimulated RAW264.7 Murine Macrophages

الملخص EN

Background.

Methicillin-resistant Staphylococcus aureus (MRSA) can stimulate massive cytokine release.

Ketamine suppresses tumor necrosis factor (TNF) secretion by MRSA-stimulated RAW264.7 macrophages, and the mechanism likely involves N-methyl-D-aspartic acid (NMDA) receptor antagonism.

The downstream effects of NMDA-mediated TNF suppression, specifically the PI3K/Akt and mTOR modulation, have not been described.

Methods.

RAW264.7 cells were stimulated for 18 hrs with 105 to 107 CFU/mL inocula of either of two prototypical community-acquired- (CA-) MRSA isolates, USA300 strain LAC and USA400 strain MW2.

Then we added the NMDA inhibitors ketamine or 2R-amino-5-phosphonopentanoate (AP5), NMDA substrate, LY294002, and rapamycin in various combinations.

Results.

NMDA inhibition suppressed TNF secretion by almost a third compared to the no-ketamine control.

When NMDA substrate was added, the TNF secretion increased by 10%.

Addition of LY294002 suppressed TNF production by macrophages by 20%.

Rapamycin exhibited a concentration-dependent TNF induction-suppression response: induction at doses of 0.1 and 1 ng/mL and suppression at 10 and 100 ng/mL.

Induction of TNF was abolished when LY294002 was added and the suppression became uniform.

Ketamine-induced suppression of TNF secretion was intensified 10–15% when rapamycin was added, but not when LY294002 was added.

Conclusion.

These findings suggest that NMDA-induced TNF suppression can be augmented by concurrent mTOR inhibition.