Nitric oxide production by murine peritoneal macrophages in vitro and in vivo treated with Phyllanthus tenellus extracts

Phyllanthus spp. are used traditionally for the treatment of viral, bacteri al and parasitic infections. Macrophages may play a central role in innate and adaptive response against several infections. Nitric oxide (NO) can be induced during macrophage activation and may exert antimicrobial activity i nhibiting the replication of several viruses or parasites. In the present s tudy, we investigated the immunomodulatory role, both in vitro and in vivo, of aqueous extracts of fresh and dried Phyllanthus tenellus as well as an acetone/water extract of the dried plant. NO production by mouse peritoneal macrophages was detected in culture supernatants. Our results demonstrated that: (1) in vitro, a concentration of 100 mug/ml fresh extract stimulated significantly (P less than or equal to 0.05) NO production in all assays a nd the optimal production was achieved at 48-h incubation; (2) 10 and 50 mg /kg fresh extract injected twice intraperitonealy primed macrophages in viv o. Priming was detected by in vitro addition of a second stimulus with 100 mug/ml extract of the fresh plant. Thus, P. tenellus was able to pre-activa te macrophages in vivo, and induce full activation in vitro. Further studie s should be carried out to better evaluate the optimal dose schedules in te rms of time/response for obtaining antiviral or other antimicrobial activit y without host damage. (C) 2001 Elsevier Science Ireland Ltd. All rights re served.