In Vitro Effect of Nitrogen and He-Ne Laser on the Apoptosis of Human Polymorphonuclear Cells from Burn Cases and Healthy Volunteers

Objective: The aim of this study was to examine the effect of He-Ne and nitrogen lasers on the apoptosis of PMN in normal versus burn patients. Background Data: Nitrogen and He-Ne laser exposure increases the apoptotic death rate for human macrophages. Inflammation is a major consequence of thermal injury, and polymorphonuclear cell (PMN) infiltration exacerbates inflammatory process through the release of proinflammatory cytokines. The apoptotic death instead of necrotic death of PMN under the situation may help to resolve inflammation.Methods: Ten healthy volunteers and 10 burn cases (30–50% burn surface) were included in the study. The PMN was separated by dextran sedimentation and density gradient centrifugation before suspending in RPMI-1640 medium supplemented with autologus serum. The cell suspension aliquoted in microwells was exposed to nitrogen (wavelength of 337 nm with power output of 3 mW) and He-Ne (LGN model no. 111, Russia, wavelength of 632.8 nm with power output of 3 mW) lasers for 10 and 5 min. The wells not exposed to laser were used as controls. After 24–36 h of incubation, the apoptotic rates were measured as percentage by morphological studies on acridine orange–ethidium bromide stained preparation using fluorescent microscope.Results: Percentage of apoptotic death increases from 32.9% (SD ± 4.14) in control PMN to 41.97% (SD± 14) in PMN exposed to nitrogen laser for 5 min and further increased to 62.7% (SD ± 15.11) with nitrogen laser exposure for 10 min. He-Ne laser exposure for 10 min increased apoptotic cell percentage to 41.9%. Increased apoptosis in PMN exposed to nitrogen laser was statistically significant (p < 0.03) both for PMN from healthy subjects and burn cases. It was significantly elevated (p = 0.005) only for PMN from healthy volunteers exposed to He-Ne laser for 10 min but not among He-Ne exposed PMN from burn cases. Conclusions: These observations support the therapeutic application of nitrogen laser to reduce inflammation and improve wound healing for burn cases.