s-nitro-n-acetylpenicillamine and Malaria

During the process of bloodfeeding by Anopheles stephensi, mammalian latent transforming growth factor beta1 (TGF-beta1) is ingested and activated rapidly in the mosquito midgut. Activation may involve heme and nitric oxide (NO), agents released in the midgut during blood digestion and catalysis of L-arginine oxidation by A. stephensi NO synthase (AsNOS). Active TGF-beta1 persists in the mosquito midgut to extended times postingestion and is recognized by mosquito cells as a cytokine. In a manner analogous to the regulation of vertebrate inducible NO synthase and malaria parasite (Plasmodium) infection in mammals by TGF-beta1, TGF-beta1 regulates AsNOS expression and Plasmodium development in A. stephensi. Together, these observations indicate that, through conserved immunological cross talk, mammalian and mosquito immune systems interface with each other to influence the cycle of Plasmodium development.

Topics: Animals; Anopheles; Humans; Intestinal Mucosa; Malaria; Nitric Oxide; Nitric Oxide Synthase; Penicillamine; Peroxynitrous Acid; Plasmodium falciparum; Transforming Growth Factor beta; Transforming Growth Factor beta1

Protective immune mechanisms to the asexual erythrocytic stages of the malaria parasite Plasmodium chabaudi AS strain include antibody-independent mechanisms. Nitric oxide (NO) is produced during the infection and indirect evidence suggests that it can contribute to the antiparasitic mechanisms. We examined the effect of an NO producer, S-nitroso-acetyl-penicillamine (SNAP), on the growth and survival in vitro of P. chabaudi AS, P. berghei and P. falciparum. Growth of the parasites was monitored by the uptake of tritiated hypoxanthine and, in the case of P. falciparum, by morphological examination in stained blood smears. DL-penicillamine and sodium nitrite, as controls, had no inhibitory activity at the concentrations used. The results showed that at SNAP concentrations of approximately 182 microM and above NO was cytotoxic to P. falciparum but, at lower concentrations, there was a cytostatic effect and some parasites resumed growth and division after NO production had ceased. Rings were less susceptible to NO effects than later stages in the asexual cycle. The antimalarial activity of NO from SNAP also extended to the rodent parasites but, under the experimental conditions used, they were less sensitive than the human species. In the cultures of P. chabaudi, increasing the numbers of noninfected erythrocytes present did not diminish the antimalarial activity of SNAP, suggesting that here at least haemoglobin was not scavenging NO significantly.

Topics: Animals; Antimalarials; Dose-Response Relationship, Drug; Erythrocytes; Female; Humans; Hypoxanthine; Malaria; Male; Mice; Nitric Oxide; Parasitemia; Penicillamine; Plasmodium berghei; Plasmodium chabaudi; Plasmodium falciparum; Tritium