Lymph node cells from BALB/c mice with chronic visceral leishmaniasis exhibiting cellular anergy and apoptosis: involvement of Ser/Thr phosphatase

• Published in: Apoptosis (London) Vol. 11; no. 11; pp. 2013 - 2029
• Main Authors: Mukherjee, Piyali, Sen, Parimal C, Ghose, Asoke C
• Format: Journal Article
• Language: English
• Published: Netherlands Springer Nature B.V 01.11.2006
• Subjects: Animals; Apoptosis; bcl-2-Associated X Protein - metabolism; Cell cycle; Cell Proliferation - drug effects; Chronic Disease; Clonal Anergy; Cricetinae; Disease Models, Animal; Enzyme Inhibitors - pharmacology; Extracellular Signal-Regulated MAP Kinases - metabolism; Inactivation; Ionomycin - pharmacology; Ionophores - pharmacology; Kinases; Leishmania donovani; Leishmania donovani - immunology; Leishmaniasis, Visceral - immunology; Lymph Nodes - cytology; Lymph Nodes - immunology; Lymphocyte Activation; Lymphocytes; Lymphocytes - cytology; Lymphocytes - immunology; Mice; Mice, Inbred BALB C; Okadaic Acid - pharmacology; Parasites; Parasitic diseases; Phosphoprotein Phosphatases - metabolism; Protein Kinase C - metabolism; Proteins; Proto-Oncogene Proteins - metabolism; Proto-Oncogene Proteins c-bcl-2; Tetradecanoylphorbol Acetate - pharmacology; Vector-borne diseases
• ISSN: 1360-8185; 1573-675X
• DOI: 10.1007/s10495-006-0088-7

Visceral leishmaniasis (VL) produced in BALB/c mice through intracardial administration of Leishmania donovani amastigotes was accompanied by hepatosplenomegaly with high organ parasite load and lymphadenopathy when followed up to 4-months or so. To elucidate the mechanism of immunosuppression associated with VL, we report here progressive impairment of the proliferative response of lymph node cells (lymphocytes) from infected animals (I-LNC) to in vitro stimulation with the combination of phorbol 12-myristate 13-acetate (PMA) and ionomycin (Io) that could be related to the downregulation of PKC and MAP kinase (ERK 1/2) activation process. Further, pretreatment of I-LNC with the protein phosphatase inhibitor okadaic acid (OA), but not with calyculin A or sodium orthovanadate, significantly restored their proliferative response as well as PMA-induced activation of PKC. A population of LNC (primarily T-lymphocytes) from chronically infected animals was shown to undergo apoptosis, the number of which increased considerably following PMA+ Io stimulation. The apoptotic pathway, which was followed through binding of cells to Annexin V, activation of caspase-3 and fragmentation of DNA, involved destabilization of mitochondria, probably as a result of downregulation of PKC and Bcl-2. Interestingly, prior incubation of I-LNC with OA reversed the state of cell cycle arrest (anergy) and apoptosis through progression of cells from G0/G1 to S and G2/M phases with transcriptional activation of IL-2 and IL-2R genes. Our results suggest that the cellular (immune) dysfunction in VL could be attributed to dephosphorylation of key molecules in the T-lymphocyte signaling pathway by Ser/Thr phosphatase leading to their inactivation.