Lasers in Surgery and Medicine The Effects of Low-Level Laser Therapy in a Rat Model of Intestinal Ischemia–Reperfusion Injury Kristin A. Kirkby, DVM, MS, 1 Ã David E. Freeman, MVB, MRCVS, PhD, 2 Allison J. Morton, DVM, MSpVM, 2 Gary W. Ellison, DVM, MS, 3 Arthur R. Alleman, DVM, PhD, 4 Paul A. Borsa, PhD, 5 Mary K. Reinhard, MS, DVM, 6 and Sheilah A. Robertson, BVMS, PhD 2 1 Seattle Veterinary Specialists, Kirkland, Washington 98034 2 Department of Large Animal Clinical Sciences, University of Florida, Gainesville, Florida 32608 3 Department of Small Animal Clinical Sciences, University of Florida, Gainesville, Florida 32608 4 Department of Physiological Sciences, University of Florida, Gainesville, Florida 32608 5 Department of Health and Human Performance, University of Florida, Gainesville, Florida 32608 6 Department of Animal Care Services, University of Florida, Gainesville, Florida 32608 Background and Objective: To investigate the effects of low-level laser therapy applied to the serosal surface of the rat jejunum following ischemia and reperfusion. Materials and Methods: Ninety-six male Sprague– Dawley rats were assigned to 15 groups and anesthetized. Small intestinal ischemia was induced by clamping the superior mesenteric artery for 60 minutes. A laser diode (70 mW, 650 nm) was applied to the serosal surface of the jejunum at a dose of 0.5 J/cm 2 either immediately before or following initiation of reperfusion. Animals were maintained under anesthesia and sacrificed at 0, 1, and 6 hours following reperfusion. Intestinal, lung, and liver samples were evaluated histologically. Results: Intestinal injury was significantly worse (P < 0.0001) in animals treated with laser and no ischemia–reperfusion injury (IRI) compared to sham. Intestinal injury was significantly worse in animals that underwent IRI and laser treatment at all time points com- pared to sham (P < 0.001). In animals that underwent IRI, those treated with laser had significantly worse intes- tinal injury compared to those that did not have laser treatment at 0 (P ¼ 0.0104) and 1 (P ¼ 0.0015) hour of reperfusion. After 6 hours of reperfusion there was no sig- nificant difference in injury between these two groups. Lung injury was significantly decreased following IRI in laser-treatment groups (P < 0.001). Conclusions: At the dose and parameters used, low-level laser did not protect against intestinal IRI in the acute phase of injury. However, laser did provide protection against distant organ injury. Failure to observe a thera- peutic response in the intestine may be due to inappropri- ate dosing parameters. Furthermore, the model was designed to detect the histologic response within the first 6 hours of injury, whereas the beneficial effects of laser, if they occur, may not be observed until the later phases of healing. The finding of secondary organ protection is important, as lung injury following IRI is a significant source of morbidity and mortality. Lasers Surg. Med. ß 2012 Wiley Periodicals, Inc. Key words: intestine; ischemia; reperfusion; lung INTRODUCTION Ischemia–reperfusion injury (IRI) is a complex cascade of events beginning with the depletion of oxygen to cells, exhaustion of ATP stores, impairment of cellular mem- brane function, and accumulation of toxic metabolites within cells [1,2]. When perfusion is restored, reactive oxygen species are quickly generated which overwhelm endogenous anti-oxidant mechanisms, leading to further cellular dysfunction [1,2]. The deleterious effects of IRI can be appreciated both in local and distant tissue [1,2]. The gastrointestinal tract is particularly sensitive to IRI and gastrointestinal ischemic injury is a common cause of morbidity and mortality in human and veteri- nary patients [1,2]. Treatment of ischemic conditions typi- cally requires surgical resection of any potentially damaged bowel. However, in some cases the portion of bowel that is affected is extensive or located in an area that is not amenable to resection. Furthermore, even if surgical resection is successful, the consequences of reper- fusion injury can be seen in distant organs. Many thera- peutic approaches to treating IRI have been studied; however, no single treatment has been found to prevent the damage associated with IRI [3,4]. Low-level laser therapy (LLLT) has been extensively investigated as a method of enhancing wound healing [5,6]. Photons emitted from lasers are absorbed by the mi- tochondria, resulting in increased cellular metabolism and ATP production [7,8]. This is followed by an increased expression of growth factors, cytokines, and genes related to cellular proliferation and migration [7,8]. Laser therapy has been shown to enhance angiogenesis, increase collagen Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Con- flicts of Interest and none were reported. Contract grant sponsor: University of Florida. *Corresponding to: Dr. Kristin A. Kirkby, DVM, MS, 2908 E Republican St, Seattle, WA 98112. E-mail: kakirkby@hotmail.com Accepted 15 July 2012 Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/lsm.22060 ß 2012 Wiley Periodicals, Inc.