The Study of Cell Killing Mechanism by Membrane Attack Complexes of Complement in the Nucleated Cells

Kim, Sang Ho; Park, Sung Hak; Chun, Myung Hoon

Abstract

The mechanism of cytolysis by complement attack of nucleated cells(NC) is of special interest in comparison to that of red blood cells. It is known that NC death by membrane attack comples, C5b-9, is caused by many factors, i.e., efficiency of complex assembly, activation of intrinsic metabolic pathway by signal transduction, cytotoxic effect of the channel itself and natural repair ability. These factors suggest that colloid osmotic lysis, known in red blood cells, does not fully explain the complement-mediated cell death of NC. In this study, the authors investigated correlation between biochemical and morphological changes to prove "Ca2+-mediated metabolic death"8~13) representing a mechanism of NC death caused by C5b-9 attack. The L1210 cells, mouse leukemic cell line carrying small complement channel(TAC5b-91) were used in the experiments. The amounts of intracellular adenine nucleotides to extracellular Ca2+, ouabain, KC1 and dextran were analyzed by bioluminescence method using luminometer. Cell viability was checked by 0.4% trypan blue dye and LDH release. Morphological observation of TAC5b-91 was done by immunocytochemical staining and electron microscope. The results were as follows: 1) The release of ATP, ADP and AMP followed by cell death was rapid and progressive along the incubation time at 37 degrees C and it was accelerated in 1.5 mM of [Ca2+]0. 2) There was no evidence of ATP repairment in the TAC5b-91. 3) Extracellular KC1(150 mM), dextran(0.66 mM) and ATP supplement(0.2 microM) could not effectively inhibit ATP depletion and cell death. Ouabain(27 and 100 microM) enhanced cell death and could not completely prevent ATP loss. 4) Most of the mitochondria showed swelling, loss of cristae and Ca2+ deposit in matrix in the electron microscopic observation. Rapid, sustained and irreversible depletion of adenine nucleotides was due to Ca2+ deposit with destruction of mitochondria and also the leakage through transmembrane channels. Moreover this energy depletion was accelerated by high extracellular Ca2+ concentration. These results indicate that Ca2+-mediated, energy exhaustion is one of the mechanisms of the metabolic cell death by C5b-9 attack of NC.