Lactobacillus acidophilus LA-5 Postbiotic Induces Apoptosis by Activating the Mitochondrial Apoptotic Pathway in Prostate Cancer

Abstract

Background and Aims: Chemotherapy uses agents that selectively target cancer cells but can also cause collateral damage to healthy tissues and lead to significant side effects. These toxic agents have major adverse effects on noncancerous tissues. It is therefore imperative to develop safe and efficacious alternative therapeutic strategies capable of inducing apoptosis. The aim of the present study was to evaluate in vitro how postbiotics derived from heat-killed Lactobacillus acidophilus LA-5 affect human prostate cancer cells.

Methods: Lactobacillus acidophilus LA-5 strain was cultured in MRS broth at a concentration of 10⁹ colony forming units (cfu) per milliliter. The activated probiotics were then heat treated at 75°C for 60 min to inactivate them and postbiotics were obtained. The inhibitory effects of heat-killed Lactobacillus acidophilus LA-5 on LNCaP and PC3 cells were assessed through an MTT assay. The apoptotic impact of postbiotics on the cells was validated using Hoechst 33342/propidium iodide (HO/PI) staining. Additionally, western blotting was employed to examine the expression of cytochrome-c (cyt-c), Bcl2, Bax, and caspase-3–9 proteins associated with the apoptotic pathway. Additionally, the levels of antioxidant and oxidant enzymes were measured in both cell lines using established colorimetric methods and commercial kits.

Results: MTT results showed that the postbiotic Lactobacillus acidophilus LA-5 had IC50 values of 10⁷ and 10⁸ cfu/mL on LNCaP and PC3 cells, respectively. HO/PI results showed postbiotic-induced apoptosis in both cell lines. Heat-killed Lactobacillus acidophilus LA-5 increased the expression of cyt-c, caspase-9, Bax, and caspase-3 protein levels and decreased Bcl2 expression in LNCaP and PC3 cell lines. However, caspase-8 was not detected. In addition, high-dose postbiotic Lactobacillus acidophilus LA-5 (10⁸ and 10⁹ cfu/mL) increased the activity of oxidants ROS and MDA and suppressed the activity of antioxidants GSH, SOD, and CAT.

Conclusions: This study demonstrated that postbiotic Lactobacillus acidophilus LA-5 from heat inactivation could cause apoptosis and impede the proliferation of LNCaP and PC3 prostate cancer cells in vitro.