Strong renal expression of heat shock protein 70, high mobility group box 1, inducible nitric oxide synthase, and nitrotyrosine in mice model of severe malaria

Introduction: Renal damage is a consequence of severe malaria, and is generally caused by sequestration of Plasmodium falciparum-infected erythrocytes in the renal microcirculation, which leads to obstruction, hypoxia, and ischemia. This triggers high mobility group box 1 (HMGB1) to send a danger signal through toll-like receptors 2 and 4. This signal up-regulates inducible nitric oxide (iNOS) and nitrotyrosine to re-perfuse the tissue, and also increases heat shock protein 70 (HSP70) expression. As no study has examined the involvement of intracellular secondary molecules in this setting, the present study compared the renal expressions of HSP70, HMGB1, iNOS, and nitrotyrosine between mice suffered from severe malaria and normal mice. Methods: C57BL/6 mice were divided into an infected group (intraperitoneal injection of 106 P. berghei ANKA) and a noninfected group. Renal damage was evaluated using hematoxylin eosin staining, and immunohistochemistry was used to evaluate the expressions of HSP70, HMGB1, iNOS, and nitrotyrosine. Results: Significant inter-group differences were observed in the renal expressions of HSP70, HMGB1, and iNOS (p= 0.000, Mann-Whitney test), as well as nitrotyrosine (p= 0.000, independent t test). The expressions of HSP70 and HMGB1 were strongly correlated (p= 0.000, R= 1.000). No correlations were observed between iNOS and HMGB, HMGB1 and nitrotyrosine, HSP70 and nitrotyrosine, or iNOS and nitrotyrosine. Conclusions: It appears that HMGB1, HSP70, iNOS, and nitrotyrosine play roles in the renal damage that is observed in mice with severe malaria. Only HSP70 expression is strongly correlated with the expression of HMGB1.