MECHANISMS OF CELL INJURY IN EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY

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Extracorporeal shock wave lithotripsy (SWL) produces renal side effects including structural damage to the microvasculature and tubular epithelium and alterations in kidney function. The objective of the proposed research is to determine the mechanisms of shock w ave (SW) cell injury in the kidney. Acoustic cavitation during SWL produces liquid microjets capable of disrupting cells, and generates reactive oxygen molecules (ROM) that may contribute to cell injury. Thus, SW-generated cavitation produces two phenomena that may cause cell injury. Therefore, we pose two hypotheses to address cellular response to these two potentially cell-disruptive features of SW treatment: 1) that shock wave-induced cavitation damages cell and organellar membranes, and 2) that SWL cell injury occurs by an ROM-mediated mechanism. We will characterize immediate versus delayed injury, determine if membrane damage is dependent upon cavitation, determine by electron spin resonance (ESR) if SWs alter membrane permeability, will assess cell functional parameters that are dependent on membrane integrity, will determine the extent of mitochondrial injury and correlate cell functional changes with alterations in cell ultrastructure. Also, we will determine if membrane"stabilizing agents" reduce the severity of cell injury. We will identify by ESR the free radical species produced by SWL and localize their site of production, characterize injury when anti-oxidant defense mechanisms are altered, determine if ROM scavengers reduce or prevent injury and will assess for mitochondrial injury resulting in alterations in cell respiration. Also, we hypothesize 3) that mechanical stress other than cavitation contributes to cell injury. We will test this idea by assessing injury when cavitation and stress are regulated. Additional studies will examine the influence of the physical parameters of SW delivery on the severity of cell injury. Experiments will be performed on cultured cell line models of the renal tubule (LLC-PK1) and the vascular endothelium (HUVEC), and on isolated kidney tubules, purified kidney mitochondria and plasma membrane preparations. Our goal is to contribute to the foundation of information necessary to establish improved SWL protocols so that renal injury is reduced or eliminated.