Involvement of the IP3 cascade in the damage to guinea-pig ventricular myocytes induced by cytotoxic T lymphocytes.
We have shown previously that the interaction between cytotoxic T lymphocytes (CTL) and ventricular myocytes, an in vitro model for heart transplant rejection, results in electrophysiological and morphological alterations indicative of overload of the intracellular [Ca2+] ([Ca2+]i). Since these deleterious effects cannot be accounted for by increased L-type Ca2+ current (ICa,L), we hypothesize that [Ca2+]i overload due to Ca2+ release from intracellular stores, e.g. sarcoplasmic reticulum (SR), is initiated by CTL-induced activation of the inositol trisphosphate (IP3) cascade. Patch-clamp and fura-2-fluorescence techniques were utilized to record transmembrane potentials and [Ca2+]i from ventricular myocytes bound to peritoneal exudate CTL (PEL). In ventricular myocyte-PEL conjugates (after 60 min), resting potential was reduced (compared with the nonconjugated state) from -80.9 +/- 0.7 to -59.9 +/- 2.5 mV, action potential amplitude from 139.5 +/- 1.4 to 80.6 +/- 1.7 mV and action potential duration to 50% repolarization (APD50) from 797 +/- 97 to 52 +/- 12 ms. The ratio of fluorescence at 340 and 380 nm (R340/380) increased from a control value (in nonconjugated myocytes) of 0.71 +/- 0.02 to 2.07 +/- 0.03, 30 min, after conjugate formation, and exceeded 4.0 at 60 min, before myocyte destruction. Heparin (50 micrograms/ml), an antagonist of IP3-induced Ca2+ release from SR channels, or U-73122 (2 microM), a phospholipase C (PLC) inhibitor (drugs were included in the pipette solution), prevented PEL-induced morphological and electrophysiological alterations. Accordingly, heparin attenuated the PEL-induced increase in [Ca2+]i; after 60 min of PEL-myocyte interaction, R340/380 was 1.15 +/- 0.09 (compared with approximately 4.0 in the absence of heparin). The results indicate that CTL-mediated damage to ventricular myocytes is, at least partially, mediated by PLC activation and IP3-induced Ca2+ release from intracellular stores. Pharmacological targeting of IP3 in heart transplant rejection is thus suggested.
Felzen
B
B
Rappaport Family Institute for Research in the Medical Sciences, Bruce Rappaport Faculty of Medicine, Bernard Katz Center for Cell Biophysics, Technion, Haifa, Israel.
Berke
G
G
Gardner
P
P
Binah
O
O
D000818:Animals; D000925:Anticoagulants / Q000494:pharmacology; D004594:Electrophysiology; D004963:Estrenes / Q000494:pharmacology; D005122:Exudates and Transudates / Q000166:cytology; D005456:Fluorescent Dyes; D016257:Fura-2; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism / Q000473:pathology; D006493:Heparin / Q000494:pharmacology; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism / Q000473:pathology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*
D000925:Anticoagulants; D004963:Estrenes; D005456:Fluorescent Dyes; D010726:Phosphodiesterase Inhibitors; D011760:Pyrrolidinones; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C074854:U 73343; D015544:Inositol 1,4,5-Trisphosphate; D006493:Heparin; D016257:Fura-2