Anti-inflammatory potential of pyocyanin in LPS-stimulated murine macrophages.

Context: Pyocyanin is a typical Pseudomonas aeruginosa virulence factor, a common Gram-negative rod responsible for a wide range of severe nosocomial infections. There is evidence indicating that pyocyanin has multiple biological activities, but little is known about anti-inflammatory properties. Objective: This study investigated pyocyanin effect on nitric oxide and cytokine production in lipopolysaccharide (LPS)-activated murine peritoneal macrophages. Materials and methods: Macrophages were incubated in the presence and absence of pyocyanin (1, 5, 10, 50, and 100 µM) with and without LPS (1 µg/mL). Nitric oxide production was determined by Griess reagent and tumor necrosis factor (TNF)-α and interleukin (IL)-1ß production was assessed by enzyme-linked immunosorbent assay. In addition, pyocyanin effects on zymosan A-induced peritonitis in mice were evaluated. Results: Pyocyanin (5 and 10 µM) decreased nitric oxide, TNF-α, and IL-1ß production independent of macrophage death. On the other hand, in vivo, pyocyanin (5 mg/kg) was not able to affect leukocyte migration into the site of inflammation. Discussion and conclusion: Thus, our findings suggest that pyocyanin exerts anti-inflammatory effects on murine peritoneal macrophages, downregulating nitric oxide, TNF-α, and IL-1ß levels, which seems to be independent of cell migration. These effects may represent a mechanism of immune evasion; nevertheless more detailed studies should be performed to confirm this hypothesis.

Morita-Baylis-Hillman adduct shows in vitro activity against Leishmania (Viannia) braziliensis associated with a reduction in IL-6 and IL-10 but independent of nitric oxide.

Current treatments for different clinical forms of leishmaniasis are unsatisfactory, highly toxic and associated with increasing failure rates resulting from the emergence of resistant parasites. Leishmania (Viannia) braziliensis is the main aetiological agent of different clinical forms of American tegumentary leishmaniasis, including the mucosal form for which treatment has high failure rates. The aim of this work was to investigate the activity of the Morita-Baylis-Hillman adduct, methyl 2-{2-[hydroxy(2-nitrophenyl)methyl])acryloyloxy} benzoate in vitro against isolates of L. (V.) braziliensis obtained from patients with different clinical manifestations of tegumentary leishmaniasis: localized cutaneous leishmaniasis, mucosal leishmaniasis and disseminated cutaneous leishmaniasis. The adduct effectively inhibited the growth of promastigotes of the different isolates of L. (V.) braziliensis (IC(50) ≤ 7·77 µg/ml), as well as reduced the infection rate of macrophages infected with these parasites (EC(50) ≤ 1·37 µg/ml). It is remarkable to state that the adduct was more effective against intracellular amastigotes (P ≤ 0·0045). The anti-amastigote activity correlated with an immunomodulatory effect, since the adduct was able to decrease the production of IL-6 and IL-10 by the infected macrophages. However, its effect was independent of nitric oxide production. This work demonstrates the anti-leishmanial activity of methyl 2-{2-[hydroxy(2-nitrophenyl)methyl])acryloyloxy} benzoate and suggests its potential in the treatment of human infections caused by L. (V.) braziliensis.

Immunomodulatory activity of ouabain in Leishmania leishmania amazonensis-infected Swiss mice.

Ouabain is a cardiotonic steroid identified as an endogenous substance of human plasma, being produced by the adrenal, pituitary, and hypothalamus. Despite the studies demonstrating the ability of ouabain to modulate inflammation and other aspects of the immune response, the effects of this substance in Leishmaniasis is unknown. The purpose of this work was to understand the immunomodulatory activity of ouabain in experimental Leishmaniasis in Swiss mice. It was demonstrated that ouabain reduced total cell numbers in the peritoneal cavity as a reflex of the inhibition of neutrophil migration induced by Leishmania (L.) Amazonensis. Furthermore, ouabain reduced TNF-α and IFN-γ levels, without cytotoxicity against peritoneal macrophages. These data showed the anti-inflammatory role of ouabain in the early events of the immune response triggered by Leishmania (L.) Amazonensis infection in murine model.