Angiotensin-converting enzyme inhibitors of Bothrops jararaca snake venom affect the structure of mice seminiferous epithelium

Abstract

Background: Considering the similarity between the testis-specific isoform of angiotensin-converting enzyme and the C-terminal catalytic domain of somatic ACE as well as the structural and functional variability of its natural inhibitors, known as bradykinin-potentiating peptides (BPPs), the effects of different synthetic peptides, BPP-10c (<ENWPHQIPP), BPP-11e (<EARPPHPPIPP), BPP-AP (<EARPPHPPIPPAP) and captopril were evaluated in the seminiferous epithelium of male mice.

Methods: The adult animals received either one of the synthetic peptides or captopril (120 nmol/dose per testis) via injection into the testicular parenchyma. After seven days, the mice were sacrificed, and the testes were collected for histopathological evaluation.

Results: BPP-10c and BPP-AP showed an intense disruption of the epithelium, presence of atypical multinucleated cells in the lumen and high degree of seminiferous tubule degeneration, especially in BPP-AP-treated animals. In addition, both synthetic peptides led to a significant reduction in the number of spermatocytes and round spermatids in stages I, V and VII/VIII of the seminiferous cycle, thickness of the seminiferous epithelium and diameter of the seminiferous tubule lumen. Interestingly, no morphological or morphometric alterations were observed in animals treated with captopril or BPP-11e.

Conclusions: The major finding of the present study was that the demonstrated effects of BPP-10c and BPP-AP on the seminiferous epithelium are dependent on their primary structure and cannot be extrapolated to other BPPs.

Keywords: Angiotensin-converting enzyme; B. jararaca; Bradykinin-potentiating peptides; Seminiferous epithelium; Spermatogenesis.

Fig. 1

Effects of angiotensin-converting enzyme (ACE) inhibitors on morphology of the seminiferous epithelium of the mouse testis. Seminiferous tubules of the right testis of control animals treated with saline solution (C) and the left testis of mice treated with captopril (CAP), (inv)BPP-10c [(inv)10c], BPP-10c (10c), BPP-11e (11e) or BPP-AP (AP). Normal structure of tubules [C, CAP, (inv)10c, and 11e], germ cells in the lumen oftubules (10c, black arrow), degenerative tubule (10c and AP, red arrow), ruptures in the epithelium (10c, arrowheads), absence of round spermatids in stage V of the seminiferous epithelium cycle (10c, asterisk), round spermatids in the adluminal compartment (AP, double asterisk) and tubules with few germ cells, green arrow). Staining: Mallory’s Trichrome [C, CAP, (inv)10c and 10c] and PAS-Hematoxylin (11e and AP)

Fig. 2

Morphometric aspects of the seminiferous tubules in mice treated with angiotensin-converting enzyme (ACE) inhibitors. a Thickness of the epithelium and diameter of tubules and lumen of the seminiferous tubules of control and treated animals. b Total support capacity of Sertoli cells during stages I, V, VII/VIII and XII of the seminiferous epithelium cycle of control and treated animals. The data are presented as the mean ± SEM. The various letters indicate significant differences between the analyzed groups as determined via one-way ANOVA followed by the Tukey test as a post hoc test (a, p < 0.001; b, p < 0.0001). C, control; CAP, captopril; (inv)10c, containing the inverted BPP-10c sequence; 10c, BPP-10c; 11e, BPP-11e; AP, BPP-AP

Fig. 3

The effects of angiotensin-coverting enzyme (ACE) inhibitors on the number of germ cell types in the seminiferous epithelium cycle. The germ cells present at stages (a) I, (b) V, (c) VII/VIII, and (d) XII of the seminiferous epithelium cycle were counted in all conditional treatments. The data are presented as the mean ± SEM; various superscripts designate significant differences between the analyzed groups as assessed using one-way ANOVA followed by the Tukey test as a post hoc test (a, p < 0.01; b, p < 0.001; c, p < 0.0001). SC, Sertoli cell; SPG(A), type A spermatogonium; SPG(B), type B spermatogonium; SP(Pl), preleptotene spermatocyte; SP(Z), zygotene spermatocyte; SP(P), pachytene spermatocyte; MF, meiotic figures; SS, secondary spermatocyte; RP, round spermatid; C, control; CAP, captopril; (inv)10c, containing the inverted BPP-10c sequence; 10c, BPP-10c; 11e, BPP-11e; AP, BPP-AP