Modulation of Signal Transduction in Leishmania donovaniinfected macrophages by a phorbol ester
Sunit Kumar Chakraborty
Department of Zoology, Raja Rammohun Roy Mahavidyalaya, Radhanagar, Hooghly, West Bengal, Pincode-712406 (India) Email : sunitc2001@gmail.com
ABSTRACT
Visceral Leishmaniasis is the most severe form of leishmaniasis affecting millions of people every year. After attachment to host macrophages parasites send signals to interior of macrophages, whereupon host-defence mechanisms are initiated to combat the infection. How this signalling mechanism can be controlled to our advantage to disable the parasite from infecting the macrophages, is the aim of this study. The role of 12-O-tetradecanoyl-phorbol-13-acetate (TPA), a stimulator of Protein Kinase C (PKC), a key enzyme in signaling pathways involving both phosphatidyl inositides and phosphatidyl choline has been investigated. TPA has the advantage of being an analogue of Diacylglycerol (DAG), the only known physiological stimulator of PKC. It has been observed that peritoneal macrophages infected with a pathogenic strain of L. donovani (AG- 83), can be inhibited upto 75% against attachment if they are exposed to TPA for 60 minutes prior to infection. The synergistic effect of PKC agonists like Calcium ion and Calcium ionophore A23187 with TPA increases % inhibition to attachment of the parasite to almost 90%. But when used alone, the extent of inhibition were 50% and 61% for Calcium ion and the ionophore respectively. Involvement of PKC was shown by use of a PKC inhibitor, Staurosporine. The inhibitor increased the parasite load in macrophages significantly but its effect could be significantly abolished by TPA, thereby strongly indicating involvement of PKC.