Inhibition of endotoxin–induced uveitis in rats using genetically engineered bacteria expressing –Melanocyte–stimulating hormone (–MSH)

Abstract

Abstract: : Purpose:: α–Melanocyte–stimulating hormone (α–MSH) is an endogenous neuroimmunomodulatory peptide that inhibits all major forms of experimental inflammation. A new technology has been developed, using probiotic yeast and bacteria as vehicles to deliver therapeutic proteins into the human body. We used genetically engineered bacteria (Lactobacillus casei) to deliver α–MSH into the eye and studied whether this microorganism can reduce the inflammatory reaction in rats with endotoxin–induced uveitis. Methods:Forty–nine male Wistar rats weighing from 178g to 227g were divided into three groups: two treatment groups and one control group. All rats received a footpad injection of lipopolissacaride (LPS) (300µg) of Escherichia coli[sc1] . Topical α–MSH (10 µL–10^–4M) was applied every 8 hours after the injection to treatment group 1; a single 10µL topical application of lactobacillus (LAB) expressing α–MSH was applied immediately after the procedure to treatment group 2; and topical balanced salt solution (10µL) was applied every 8 hours to control group 3. Twenty–four hours later, protein levels were measured and the total number of inflammatory cells was counted in the aqueous humor. Clinical inflammation was graded by observation of conjunctival hyperemia, miosis, exudates, and hypopyon. All rats were sacrificed and the eyes were enucleated and fixated for pathology analysis. [sc1]Is all the necessary information included here? Results: The topical application of α–MSH and LAB expressing α–MSH significantly reduced clinical inflammation, protein levels, and the total number of inflammatory cells in the aqueous humor (p<0.01). There was no statistical difference between the group treated with α–MSH and the group treated with LAB expressing α–MSH in any of the analyzed parameters (p>0.1). Conclusions:Topical LAB expressing α–MSH reduced both the total number of inflammatory cells and protein levels in aqueous humor, and reduced clinical signs of acute ocular inflammation at a rate similar to α–MSH alone. The results suggest that genetically engineered bacteria (LAB) expressing α–MSH might be a useful agent against acute ocular inflammatory reaction, thereby reducing the frequency of instillation and increasing patient compliance.

Keywords: drug toxicity/drug effects • gene/expression • inflammation