Polymorphonuclear leukocyte injury by methylglyoxal and hydrogen peroxide: a possible pathological role for enhanced oxidative stress in chronic kidney disease

BACKGROUND: Accelerated burst of polymorphonuclear leukocytes (PMNs) may be involved in the primary pathology of enhanced oxidative stress in patients with chronic kidney disease (CKD); however, the precise mechanism remains unknown. Methylglyoxal (MGO), an alpha-oxoaldehyde reportedly elevated in CKD, could induce apoptosis in several cell lines, and generates radicals by the reaction with hydrogen peroxide (H(2)O(2)). Thus, we tested if a high MGO of uraemic milieu could play a role in PMN injury by interaction with H(2)O(2). METHOD: Cellular viability of PMNs, isolated from healthy volunteers, was tested by ATP chemiluminescence levels under MGO and/or H(2)O(2), or 4-beta phorbol 12-beta-myristate 13-alpha-acetate (PMA). Superoxide anion (O(2)(-)) generation and apoptosis were measured by the reduction of ferricytochrome C and fluorocytometric analysis, respectively. Plasma MGO levels were measured by mass spectometry in 29 CKD patients. RESULTS: At low levels of MGO (1-10 microM) and H(2)O(2) (12.5 microM), no differences were found in cellular viability as compared to controls, whereas their combination significantly decreased PMN viability. PMA stimulation enhanced cellular injury of MGO by a function of MGO levels and preincubation with 5,5-dimethyl-1-pyrroline-N-oxide (free radical trap agent) attenuated it. MGO suppressed O(2)(-) generation by PMA, while it accelerated apoptotic ratios in PMNs. Significant increases of plasma MGO and C-reactive protein levels were found by a function of CKD stage, and clinical level of MGO could induce PMN injury in combination with H(2)O(2). CONCLUSION: These results indicate the combinatory effect of MGO and H(2)O(2) on PMN oxidative injury, and this pathology may be linked to enhanced oxidative stress in CKD.