g(m1)-ganglioside and chelerythrine

Sphingosine-1-phosphate (S1P) protects neonatal rat cardiac myocytes from hypoxic damage through unknown signaling pathways. We tested the hypothesis that S1P-induced cardioprotection requires activation by the epsilon-isoform of protein kinase C (PKC epsilon) by subjecting hearts isolated from PKC epsilon knockout mice and wild-type mice to 20 min of global ischemia and 30 min of reperfusion. Pretreatment with a 2-min infusion of 10 nM S1P improved recovery of left ventricular developed pressure (LVDP) in both wild-type and PKC epsilon knockout hearts and reduced the rise in LV end-diastolic pressure (LVEDP) and creatine kinase (CK) release. Pretreatment for 2 min with 10 nM of the ganglioside GM-1 also improved recovery of LVDP and suppressed CK release in wild-type hearts but not in PKC epsilon knockout hearts. Importantly, GM-1 but not S1P, increased the proportion of PKC epsilon localized to particulate fractions. Our results suggest that GM-1, which enhances endogenous S1P production, reduces cardiac injury through PKC epsilon-dependent intracellular pathways. In contrast, extracellular S1P induces equivalent cardioprotection through PKC epsilon-independent signaling pathways.

Topics: Alkaloids; Animals; Animals, Newborn; Benzophenanthridines; Blotting, Western; Cells, Cultured; Creatine Kinase; Enzyme Inhibitors; G(M1) Ganglioside; Isoenzymes; Lysophospholipids; Mice; Mice, Knockout; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocardium; Phenanthridines; Protein Kinase C; Signal Transduction; Sphingosine; Ventricular Function, Left

Sialated glycosphingolipids (gangliosides) were recently shown to induce internalisation of the CD4 Ag in lymphoid cells and dissociation of p56lck from CD4 (Repke et al. (1992) J. Immunol. 149, 2585-2591; Saggioro et al. (1993) J. Biol. Chem. 268, 1368-1375). The findings presented in this paper show that GM1 induces internalisation and the eventual degradation of the CD4 Ag also in the monocytic cell line U937. GM1 effects are independent of a possible activation of protein kinase C, as enzyme inhibitors which effectively blocked phorbol esters effects did not prevent GM1-induced CD4 internalisation and degradation. GM1 effects were also independent of a possible action on a CD4 associated kinase activity as we show that U937 cells lack any CD4-associated kinase activity.

Topics: Alkaloids; Benzophenanthridines; CD4 Antigens; Down-Regulation; Endocytosis; Enzyme Activation; G(M1) Ganglioside; Humans; In Vitro Techniques; Lymphocyte Specific Protein Tyrosine Kinase p56(lck); Phenanthridines; Protein Kinase C; Proto-Oncogene Proteins; Staurosporine; Tumor Cells, Cultured