Histomorphometric Evaluation of the Renal Corpuscles of Mice Treated With Poly-ε-caprolactone Micro-spheres Containing Usnic Acid From the Acute Toxicity Test

Introdution: Usnic acid, a hydrophobic lichen metabolite, has been highlighted in the literature with several biological activities, such as: anti-inflammatory, analgesic, antimicrobial, antiviral, antiparasitic, gastroprotective, antitumor and cicatrizant. Despite the fact that the usnic acid presents several biological activities, its use as a therapeutic agent has not yet been possible due to its inconvenient physico-chemical properties, such as low solubility, toxicity and difficult interaction with biological barriers. Thus, the incorporation of the usnic acid (UA) in controlled release systems, such as microparticles, can reduce the toxicity of this compound and make it a viable alternative for therapeutic application. Objective: To analyze the properties of poly-e-caprolactone microspheres incorporated with usnic acid on the histomorphometry of the renal corpuscles of Swiss mice submitted to the acute toxicity test. Methodology: The groups treated with vehicle (0.9% NaCl and 5% cremophor), usnic acid (2000, 300 and 50 mg/kg) and microspheres incorporated with usnic acid (UA-Micro) in the dose of 2000 mg/kg were subjected to the acute toxicity test according to Organisation for Economic Co-operation and Development (OECD – Guideline, 423). Fragments of renal tissue were removed for preparation of histological slides, subsequently stained with Hematoxylin and Eosin. The morphometric analysis of renal capsule diameters was performed using the IMAGE software from the photomicrographs (final magnification 790 μm). Statistical analysis of the renal capsule diameters was performed using Variance (ANOVA), followed by the Tukey test. Results and Discussion: Treatment with UA-Micro (2000 mg/kg) and UA (50 mg/kg) did not show histomorphometric changes in the glomerular capsule, but treatments with UA (2000 and 300 mg/kg) caused histomorphometric changes in the glomerular capsule (**** p <0.0001 and *** p <0.001), when compared with the control group. Conclusion: Poly-e-caprolactone microspheres containing usnic acid reduced the toxicity of the usnic acid to the renal corpuscles.