Acetyl-L-carnitine improves erectile function in bilateral cavernous nerve injury rats via promoting cavernous nerve regeneration

Abstract

Background: Neurogenic erectile dysfunction (NED) caused by cavernous nerve (CN) injury is a typical complication after pelvic surgery, which lacks efficient treatments. Acetyl-L-carnitine (ALCAR) has been proven to promote nerve repair.

Objectives: To investigate the effect and potential mechanism of ALCAR in the treatment of NED.

Materials and methods: Thirty-two rats were randomly divided into bilateral CN injury (BCNI) group, BCNI + lower-dose ALCAR (50 mg/kg/day) group, BCNI + higher-dose (100 mg/kg/day) group, and sham-operated group. Erectile function was assessed 14 days after daily intraperitoneal injection of ALCAR or placebo. The penile tissues were gathered for subsequent histological and molecular biological analysis. Rat Schwann cell (SC) line S16 was used to verify the mechanism of ALCAR in vitro.

Results: We found that the erectile function of the rats in the BCNI group was severely impaired, which was improved considerably in both BCNI+ALCAR-LD and BCNI+ALCAR-HD groups. Also, we observed decreased smooth muscle and increased collagen content in the corpus cavernosum in the BCNI group. The expressions of fibrosis markers transforming growth factor-beta (TGF-β), connective tissue growth factor (CTGF), and Smad 2/3 were significantly up-regulated in the BCNI group. The above changes were alleviated after the administration of lower and higher-dose ALCAR. Meanwhile, the nitric oxide (NO)/cyclic guanosine monophosphate pathway (cGMP) was promoted and the Ras homolog gene family member A (RhoA)/Rho-associated protein kinase (ROCK) pathway was inhibited in the corpus cavernosum of BCNI rats after ALCAR treatment, accompanied by increased neuronal nitric oxide synthase (nNOS) and down-regulated tyrosine hydroxylase (TH). In vitro, ALCAR promoted the migration and proliferation of SC and increased the expression of 22-kD peripheral myelin protein and nerve growth factor (NGF). Further, rats treated with ALCAR had high expression of ATF3 and S100 in the distal nerve tissues of the CN extrusion site.

Discussion and conclusion: ALCAR could promote nerve repair and regeneration, inhibit penile fibrosis, and improve penile erection by promoting the proliferation and migration of SC and the secretion of NGF. Our study confirms that ALCAR may be a potential treatment strategy for NED.

Keywords: Schwann cell; acetyl-L-carnitine; bilateral cavernous nerve injury; fibrosis; neurogenic erectile dysfunction.