PUTATIVE EFFECTS OF CYANOCOBALAMIN IN THE REGULATION OF INFLAMMATORY RESPONSES, OXIDATIVE STRESS AND PATHOPHYSIOLOGICAL EVENTS DURING SEVERE STAGE OF HUMAN AFRICAN TRYPANOSOMIASIS

Abstract

Human African Trypanosomiasis (HAT) is a neglected tropical disease caused by T. b. rhodesiense and T. b. gambiense, with tsetse fly (Glossina spp) being the known vector. T. b. rhodesiense causes acute form of HAT in Africa. The severe late stage of the disease is characterized by infiltration of the brain through the blood brain barrier (BBB) as well as overwhelming inflammation and oxidative stress. Treatment of HAT is reliant on the stage of the disease and melarsoprol remains the drug of choice for treatment of late-stage HAT despite the fact that it causes post-treatment reactive encephalopathy (PTRE). It therefore implies that, new treatment strategies that control the breach of the BBB as well as inflammatory reactions and oxidative stress may benefit those on treatment. This study utilized cyanocobalamin (vitamin B12), a well characterized anti-inflammatory and anti-oxidant molecule to determine its effects on T. b. rhodesiense-driven deleterious events. Therefore, the objective was to determine the effects of cyanocobalamin in the regulation of immune response during T. b. rhodesiense infection. Mice were randomly assigned into four groups each containing 8 mice; with group one being the control. Group two was infected with 5.0 x 104 KETRI 2537 T.b.rhodesiense; group three was supplemented with 8mg/kg of vitamin B12 for two weeks before infection. For group four, administration of vitamin B12 was started 4 days post infection (dpi). The general health of the mice was assessed using rapid murine coma and behavior scale (RMCBS), while parasiteamia was determined microscopically. At 42 dpi, the mice were sacrificed to obtain blood, tissues and organs for various analyses. The statistical analysis was done by GraphPad Prism software package. One-way ANOVA was used to compare the treatment groups with controls, Tukey’s post-hoc test for internal comparisons and Log-rank (Mantel-Cox) test for survival analysis. The results were given as a mean ±SEM with the level of significance set at P <0.05.The results showed that vitamin B12 enhanced the survival rate of T.b.rhodesiense infected mice independent of parasitemia of antilog 8.7 organism/ml and prevented T.b.rhodesiense-induced disruption of the BBB. Notably, T.b.rhodesiense-induced hematological alteration leading to microcytic hypochromic anemia and leukocytosis was nullified in mice administered with vitamin B12. T.b.rhodesiens-induced dyslipidemia was reversed by vitamin B12. T.b.rhodesiense-induced elevation of the liver alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, total bilirubin, urea, uric acid and creatinine for kidney damage markers were attenuated by vitamin B12. Vitamin B12 blocked T.b.rhodesiense-driven rise in pro-inflammatory cytokines (TNF-α and IFN-γ), nitric oxide (NO) and malonaldehyde (MDA). T.b.rhodesiense-induced depletion of glutathione (GSH) levels were attenuated in the presence of vitamin B12 in the brain, spleen and liver tissues; a clear indication of the anti oxidant activity of vitamin B12. The histological analysis of the brain and liver confirmed T.b.rhodesiense-driven damage of these vital organs; which was ameliorated by vitamin B12. In conclusion, treatment with vitamin B12 potentially protects against various pathological events associated with severe late-stage HAT and presents a great opportunity for further scrutiny to develop an adjunct therapy for severe late-stage HAT.