Pneumococci stimulate the production of the inducible nitric oxide synthase and nitric oxide by murine macrophages

The role of nitric oxide (NO) in the pathophysiology of gram-positive sepsi s is uncertain. In inflammatory conditions, high-output NO production is ca talyzed by the enzyme inducible nitric oxide synthase (iNOS), The ability o f 2 strains of pneumococci, pneumococcal cell wall preparations, and purifi ed pneumococcal capsule (Pnu-Imune 23) to trigger the production of iNOS pr otein and NO in RAW 264.7 murine macrophages was tested. Live pneumococci, oxacillin-killed pneumococci, and pneumococcal cell wall preparations stimu lated the production of iNOS and NO by RAW 264.7 cells in the presence, but not the absence, of low concentrations of recombinant murine interferon-ga mma, In contrast, purified pneumococcal capsule induced little or no iNOS o r NO production by these cells. Thus, pneumococci stimulate high-output NO production by murine macrophages, The potential role of NO in the pathogene sis of pneumococcal sepsis deserves further study.