The Intervention Of Riluzole On LPS Induced Endophthalmitis In Rats

Endophthalmitis is vision-threatening through causing severe inflammation and destruction of the retina, resulting in worse visual prognosis even with prompt treatment. Clinical symptoms of endophthalmitis include severe pain, chemosis, periorbital swelling, extreme proptosis, fever and polymorphonuclear leukocytosis. Visual function outcome is determined by the infectious process and the host immune response. Bacterial endophthalmitis can occur as a result of intraocular surgery, penetrating eye injury or metastasis of bacteria to the eye from distant infection. Current treatment recommendations for bacterial endophthalmitis include intravitreal injections of vancomycin(1.0 mg/ml) for Gram-positive bacteria and amikacin(0.4 mg/ml) or ceftazidime(2.2 mg/ml) for Gram-negative bacteria. Antibiotics can eliminate the organism, but cannot reverse the damage caused by bacterial products. Factors that contribute to severity of bacterial infections include secreted toxins and cell surface components that result in direct tissue damage, induction of host inflammatory response, or both. Study showed that Escheriehia coli lipopolysaccharide(LPS) can induce severe inflammatory responses in the eyes.Massive neutrophils infiltration,high levels expression of TNF-α and IL-1β in vitreous cavity were observed[4].Excessive immune response can cause severe cellular damage.The inflammatory cascade activated by the specific toxic effects of the pathogen ultimately determines the final anatomical and functional visual outcome[5]. Concomitant administration of intravitreal steroids, such as dexamethasone, with antibiotics to minimize ocular inflammation and bystander damage caused by the immune system during endophthalmitis has produced mixed results.Although studies have been done to investigate retinal innate immunity in endophthalmitis, much less is known about how to protect the retina and regulate the retinal inflammation. Riluzole, a drug acting on several types of ion channels and inhibiting neuronal glutamate release, can protect neuronal damage in rodent models of global and focal cerebral ischemia[6], and in spinal cord injury[7]. Study has showed riluzole improves functional recovery after ischemia in the rat retina[8]. It prevents or attenuats ischemia-induced retinal cell death(necrosis and apoptosis) and reduced the activation of p-JNK, c-jun phosphorylation, and the increase of cytoskeletal proteins induced by ischemia. Therefore, riluzole may be a major drug for use in protection against retinal injury.Purpose This study evaluated the possible therapeutic effectiveness of riluzole in LPS induced endophthalmitis in rats, and the mechanism was investigated.Methods and material Sprague-Dawley rats were randomly divided into 3 groups. Group 1: the vehicle-injected group. Group 2:LPS inoculated group. Group 3: LPS inoculated with riluzole treatment group. The right eyes of rats in group 2 and group 3 were injected with LPS. The vehicle-injected rats received intravitreal injections of balanced salt solution(BSS), respectively. The left eyes were uninjected. Intraperitoneal injections of riluzole were given to the rats in group 3 before and after LPS inoculation, once daily during the next three days. Inflammation was graded in vivo and by histopathology. Clinical signs were recorded at different times after injections. Oculars were harvested at 6h,12 h,24h,48 h,3d,5d,7d and processed for histopathology and immunohistochemistry for glutamine synthetase(GS).The expression of GS was measured by real-time quantitative PCR at 48 h after molding. TUNEL were analyzed to find whether riluzole can protect retina cells by inhibiting glutamte realse in LPS induced ocular inflammation. All the data were analyzed by SPSS 21.0 statistical package. The mean among three groups was used the ANVOA. The relation of two variables was analyzed with LSD test. Less than 0.05 was considered statistical significance.Results Riluzole treatment reduced fibrin exudations, inflammatory cells infiltration in the eyes injected with LPS. The Clinical inflammation scores of treated group were lower at 24 h, 48 h and 3d. No significant inflammation was observed in control eyes. 6 hours post inoculation, eyes from the LPS inoculated group demonstrated an intense inflammatory reaction at slit lamp examination, including conjunctival edema and mild hyperemia. Conjunctival hyperemia around the cornea, hypopyo and coneal edema were observed at 24 h. Rats that received rliluzole treatment demonstrated delay in onset of inflammation. Peripheral blood leukocytes infiltrated in the eyes injected with LPS. There were less inflammation cells in treated rats. GS was mainly expressed in ganglionic layer(GCL) and inner nuclear layer(INL). Correspondingly, according to the immunohistochemical staining for GS, riluzole treatment significantly suppressed the expression of GS in retina indicating that Müller cells activation were inhibited at 6h, 12 h, 24 h, 48 h, 3d. Retinas were less stained for GS in the control group. The results of PCR for GS at 48 h showed the same tendency. The vitreous in group 3 contained lower levels of glutamate compared to group 2 after 6h molding. It showed less apoptosis cells in the retinas of group 3 which indicating neuroprotective effect of riluzole.Conclusions Riluzole can suppress the LPS induced intraocular inflammation by inhibiting Müller cells activation, regulate glutamate metabolism and protect retina cells from glutamate neurotoxicity. This study suggests that riluzole may be beneficial in the treatment of endopthamitis complied with traditional drugs.