Effects of larval extracts from identified Protaetia brevitarsis seulensis against benign prostatic hyperplasia induced by testosterone in rats

Abstract

Protaetia brevitarsis seulensis is an animal-based medicine used traditionally in China, Japan, and Korea to treat hepatic disorders; it has been shown to possess various pharmacological effects such as antibacterial and antioxidant activities. In this study, we investigated the effects of P. brevitarsis on a testosterone-induced benign prostatic hyperplasia (BPH) rat model. To establish the BPH model, the animals were administered a subcutaneous injection of testosterone daily for 28 days. P. brevitarsis was administered by oral gavage at doses of 12.5, 25, and 50 mg/kg for 28 days, along with testosterone injection. P. brevitarsis treatment markedly decreased the absolute and relative prostate weight of BPH animals. The levels of dihydrotestosterone was reduced in P. brevitarsis-treated animals compared to those in the BPH animals. Histological analysis of the prostate showed that P. brevitarsis treatment effectively suppressed the testosterone-induced hyperplasia of prostatic epithelial cells, which was accompanied by reductions in the PCNA and Ki-67 expressions in prostatic tissues. These results indicate that P. brevitarsis effectively suppresses testosterone-induced development of BPH, and thus, is a potential therapeutic agent for BPH.

Keywords: Protaetia brevitarsis seulensison; benign prostatic hyperplasia; dihydrotestosterone; testosterone.

FIGURE 1

Effects of PBE on absolute and relative prostate weights. At necropsy, whole prostates were immediately removed and weighted. Relative prostate weight was calculated as the ratio of prostate weight to body weight. (a) Absolute prostate weight, (b) Relative prostate weight. VC, animals receiving corn oil and PBS; BPH, animals received TP and PBS; Fin, animals receiving TP and finasteride; BPH + PBE 12.5, 25, and 50, animals receiving TP and PBE at rates of 12.5, 25, and 50 mg/kg, respectively; PBE, animals receiving only PBE (50 mg/kg). Data are presented as mean ± standard deviation (SD) (n = 6). ##Significant difference at p < .01 compared with VC. *,**Significant difference at p < .05 and p < .01, compared with BPH, respectively

FIGURE 2

Effects of PBE on the serum DHT level. The levels of DHT in the serum were evaluated using an enzyme‐linked immunosorbent assay (ELISA) kit. VC, animals receiving corn oil and PBS; BPH, animals receiving TP and PBS; Fin, animals receiving TP and finasteride; BPH + PBE 12.5, 25, and 50, animals receiving TP and PBE at rates of 12.5, 25, and 50 mg/kg, respectively; PBE, animals receiving only PBE (50 mg/kg). Data are presented as mean ± standard deviation (SD) (n = 6). ##Significant difference at p < .01 compared with VC. *,**Significant difference at p < .05 and p < .01 compared with BPH, respectively

FIGURE 3

Effects of PBE on epithelial hyperplasia in the prostate. The prostate tissues were embedded in paraffin, sectioned to 4 μm thickness and stained with hematoxylin and eosin (magnification ×200). VC, animals receiving corn oil and PBS; BPH, animals receiving TP and PBS; Fin, animals receiving TP and finasteride; BPH + PBE 12.5, 25, and 50, animals receiving TP and PBE at rates of 12.5, 25, and 50 mg/kg, respectively; PBE, animals receiving only PBE (50 mg/kg)

FIGURE 4

Effects of PBE on the expression of PCNA protein. Immunoblotting was performed according to a previous study (17). The following primary antibodies and dilutions were used: anti‐PCNA (1:1,000 dilution, Abcam) and anti‐β‐actin (1:2000 dilution, Cell Signaling). To evaluate the relative ratio of protein expression, densitometric band values were determined by Chemi‐Doc (Bio‐Rad Laboratories). (a) PCNA expression, (b) relative expression value. VC, animals receiving corn oil and PBS; BPH, animals receiving TP and PBS; Fin, animals receiving TP and finasteride; BPH + PBE 12.5, 25, and 50, animals receiving TP and PBE at rates of 12.5, 25, and 50 mg/kg, respectively; PBE, animals receiving only PBE (50 mg/kg). Data are presented as mean ± standard deviation (SD) (n = 6). ##Significant difference at p < .01 compared with VC. *,**Significant difference at p < .05 and p < .01 compared with BPH, respectively

FIGURE 5

Effect of PBE on the expression of Ki‐67 protein in the prostate. The expression of Ki‐67 in the prostate was evaluated by immunohistochemistry using a commercial kit. The anti‐mouse Ki‐67 antibody was purchased from Santa Cruz Biotechnology and used at a 1:200 dilution. VC, animals receiving corn oil and PBS; BPH, animals receiving TP and PBS; Fin, animals receiving TP and finasteride; BPH + PBE 12.5, 25, and 50, animals receiving TP and PBE at rates of 12.5, 25, and 50 mg/kg, respectively; PBE, animals receiving only PBE (50 mg/kg)

FIGURE 6

Effect of PBE on hepatic enzyme activities. To investigate the toxic effect of PBE, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities were determined using a Fuji Dri‐Chem 4000i automatic analyzer. (a) ALT, (b) AST. VC, animals receiving corn oil and PBS; BPH, animals receiving TP and PBS; Fin, animals receiving TP and finasteride; BPH + PBE 12.5, 25, and 50, animals receiving TP and PBE at rates of 12.5, 25, and 50 mg/kg, respectively; PBE, animals receiving only PBE (50 mg/kg). Data are presented as mean ± standard deviation (SD) (n = 6)