Targeting Wistar rat as a model for studying benign, premalignant and malignant lesions of the prostate

Subchronic intake of arsenic at environmentally relevant concentrations causes histological lesions and oxidative stress in the prostate of adult Wistar rats

The prostate gland is one of the main sites of hyperplasia and cancer in elderly men. Numerous factors have been demonstrated to disrupt prostate homeostasis, including exposure to environmental pollutants. Arsenic is a metalloid found ubiquitously in soil, air, and water, which favors human poisoning through the involuntary intake of contaminated drinking water and food and has harmful effects by increasing the oxidative stress response. This study aimed to investigate the effects of prolonged exposure to arsenic at environmentally relevant concentrations on the prostate biology of adult Wistar rats. Thirty 80-day-old male rats were divided into three experimental groups. Rats from the control group received filtered water, whereas animals from the arsenic groups ingested 1 mg L-1 and 10 mg L-1 of arsenic, in the form of sodium arsenite, daily. The arsenic solutions were provided ad libitum in the drinking water for eight weeks. Our results showed that 1 mg L-1 and 10 mg L-1 of arsenic made the prostate susceptible to evolving benign and premalignant histopathological changes. While the ingestion of 1 mg L-1 of arsenic reduced SOD activity only, 10 mg L-1 diminished SOD and CAT activity in the prostate tissue, culminating in high MDA production. These doses, however, did not affect the intraprostatic levels of DHT and estradiol. In conclusion, exposure to arsenic at environmentally relevant concentrations through drinking water induces histological and oxidative stress-related changes in the prostate of adult rats, strengthening the between arsenic exposure and prostate disorders.

Prostatic morphological changes throughout life: Cytochemistry as a tool to reveal tissue aging markers

The prostate undergoes normal or pathological morphological changes throughout life. An understanding of these changes is fundamental for the comprehension of aging-related pathological processes such as benign prostatic hyperplasia (BPH) and cancer. In the present study, we show some of these morphological changes, as well as histochemical techniques like Weigert's resorcin-fuchsin method, Picrosirius Red, and Gömöri's reticulin for use as tools in the study of prostate tissue under light microscopy. For this purpose, prostates of the Mongolian gerbil (n = 9), an experimental model that develops BPH spontaneously, were analyzed at three life stages: young (1 month old), adult (3 months old), and old (15 months old). The results showed that fibrillar components such as collagen, and reticular and elastic fibers, change throughout life. In young animals, the prostate has cuboidal epithelium surrounded by thin layers of smooth muscle, continuous collagen fibers, winding reticular fibers, and sporadic elastic fibers. With adulthood, the epithelium becomes columnar, encircled by compacted muscle cells among slender collagen fibers, elongated reticular fibers, and linear elastic fibers. In aging individuals, the prostate's epithelium stratifies, surrounded by thick muscle layers among dense collagen fibers, disordered reticular fibers, and elastic fibers in different planes. We also identified a few accumulations of lipid droplets and lipofuscin granules in adult animals and high accumulation in old animals evidenced by Oil red O and Gömöri-Halmi techniques, respectively. The histochemical techniques presented here have been demonstrated to be useful and accessible tools in prostate studies. RESEARCH HIGHLIGHTS: Cytochemical techniques to study prostate morphology. The prostate changes with age.

Lifelong exercise training promotes the remodelling of the immune system and prostate signalome in a rat model of prostate carcinogenesis

This work aimed to understand how lifelong exercise training promotes the remodelling of the immune system and prostate signalome in a rat model of PCa. Fifty-five male Wistar rats were divided into four groups: control sedentary, control exercised, induced PCa sedentary and induced PCa exercised. Exercised animals were trained in a treadmill for 53 weeks. Pca induction consisted on the sequential administration of flutamide, N-methyl-N-nitrosourea and testosterone propionate implants. Serum concentrations of C-reactive protein (CRP) and tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) were not different among groups. Peripheral levels of γδ T cells were higher in Pca exercised group than in the PCa sedentary group (p < 0.05). Exercise training also induced Oestrogen Receptor (ESR1) upregulation and Mitogen-activated Protein Kinase 13 (MAPK13) downregulation, changed the content of the phosphorylated (at Ser-104) form of this receptor (coded by the gene ESR1) and seemed to increase Erα phosphorylation and activity in exercised PCa rats when compared with sedentary PCa rats. Our data highlight the exercise-induced remodelling of peripheral lymphocyte subpopulations and lymphocyte infiltration in prostate tissue. Moreover, exercise training promotes the remodelling prostate signalome in this rat model of prostate carcinogenesis.

Gold nanoparticle intratesticular injections as a potential animal sterilization tool: Long-term reproductive and toxicological implications

This study aimed to evaluate the gold nanoparticles (AuNPs) animal sterilizing potential after intratesticular injections and long-term adverse reproductive and systemic effects. Adult male Wistar rats were divided into control and gold nanoparticle (AuNPs) groups. The rats received 200µL of saline or AuNPs solution (16µg/mL) on experimental days 1 and 7 (ED1 and ED7). After 150 days, the testicular blood flow was measured, and the rats were mated with females. After mating, male animals were euthanized for histological, cellular, and molecular evaluations. The female fertility indices and fetal development were also recorded. The results indicated increased blood flow in the testes of treated animals. Testes from treated rats had histological abnormalities, shorter seminiferous epithelia, and oxidative stress. Although the sperm concentration was lower in the AuNP-treated rats, there were no alterations in sperm morphology. Animals exposed to AuNPs had decreased male fertility indices, and their offspring had lighter and less efficient placentas. Additionally, the anogenital distance was longer in female fetuses. There were no changes in the histology of the kidney and liver, the lipid profile, and the serum levels of LH, testosterone, AST, ALT, ALP, albumin, and creatinine. The primary systemic effect was an increase in MDA levels in the liver and kidney, with only the liver experiencing an increase in CAT activity. In conclusion, AuNPs have a long-term impact on reproduction with very slight alterations in animal health. The development of reproductive biotechnologies that eliminate germ cells or treat local cancers can benefit from using AuNPs.

Altered expression of the vitamin D metabolizing enzymes CYP27B1 and CYP24A1 under the context of prostate aging and pathologies

Low circulating levels of vitamin D are common at older ages and have been linked to an increased risk of prostate disease, including cancer. However, it has not yet been determined whether aging affects the ability of prostate cells to locally metabolize vitamin D into its active metabolite calcitriol and thus mediate the vitamin D signaling in autocrine and paracrine ways. By using a suitable rat model to interrogate spontaneous prostatic modifications over the course of aging, here we showed that both CYP27B1 and CYP24A1 enzymes, which are key players respectively involved with calcitriol synthesis and deactivation, were highly expressed in the prostate epithelium. Furthermore, as the animals aged, a drastic reduction of CYP27B1 levels was detected in total protein extracts and especially in epithelial areas of lesions, including tumors. On the other hand, CYP24A1 expression significantly increased with aging and remained elevated even in altered epithelia. Such intricate unbalance in regard to vitamin D metabolizing enzymes was strongly associated with reduced bioavailability of calcitriol in the senile prostate, which in addition to decreased expression of the vitamin D receptor, further limits the protective actions mediated by vitamin D signaling. This evidence was corroborated by the increased proliferative activity exactly at sites of lesions where the factors implicated with calcitriol synthesis and responsiveness had its expression inhibited. Taken together, our results emphasize a set of modifications over the course of aging with a high potential to hamper vitamin D signaling on the prostate. These findings highlight a crosstalk between vitamin D, aging, and prostate carcinogenesis, offering new potential targets in the prevention of malignancies and other aging-related disorders arising in the gland.

The influence of Castanea sativa Mill. flower extract on hormonally and chemically induced prostate cancer in a rat model

Prostate cancer (PCa) is one of the most common cancers in men, with a huge impact on their health. The use of Castanea sativa Mill. flowers (CFs) in beverages has been reported, through ancestral claims, as having health benefits. In vitro research has evidenced the properties of CFs, such as antitumor and antioxidant activities. This study aimed to evaluate the effects of CF extract in an animal model of PCa. Forty male Wistar Unilever rats were randomly assigned to four groups: control, induced, control + CF, and induced + CF groups. Animals from the induced groups were exposed to a multistep protocol for PCa induction. The CF extract, rich in trigalloyl-HHDP-glucoside and obtained via decoction, was administered to the CF groups in drinking water (3 mg per animal per day) for 49 weeks. Animals were sacrificed at 61 weeks of age. Regarding the effects of CFs on dorsolateral prostate tumorigenesis, no significant differences were observed between the induced and induced + CF groups. However, animals exposed to the CF extract showed fewer inflammation areas on the dorsolateral prostate lobe than those not exposed to CF. Moreover, the CF extract alleviated the hepatic oxidative stress associated with the multistep protocol, resulting in lower levels of lipid peroxidation. These results suggest that CF extract has antioxidant and anti-inflammatory properties.

Melatonin ameliorates degenerative alterations caused by age in the rat prostate and mitigates high-fat diet damages

Imbalance of sexual steroids milieu and oxidative stress are often observed during aging and correlated to prostate disorders. Likewise, high-fat intake has been related to prostate damage and tumor development. Melatonin (MLT) is an antioxidant whose secretion decreases in elderly and is also suggested to protect the gland. This study evaluated the impact of a long-term high-fat diet during aging on prostate morphology and antioxidant system of rats and tested the effects of MLT supplementation under these conditions. Male rats were assigned into four groups: control, treated with MLT, high-fat diet and high-fat diet treated with MLT. The high-fat diet was provided from the 24th week of age, MLT from the 48th (100 μg/kg/day) and rats were euthanized at the 62nd week. The high-fat diet increased body weight, retroperitoneal fatness, glycaemia, and circulating estrogen levels. It aggravated the aging effects, leading to epithelial atrophy (∼32% reduction of epithelial height) and collagen fibers increase (83%). MLT alone did not alter biometric and physiological parameters, except for the prostate weight decrease, whereas it alleviated biometric as well as ameliorated acinar atrophy induced by high-lipid intake. Systemic oxidative stress increased, and prostatic glutathione peroxidase activity decreased fivefold with the high-fat diet despite the indole. Regardless of the diet, MLT triggered epithelial desquamation, reduced androgen receptor-positive cells, increased smooth muscle layer thickness (12%), decreased at least 50% corpora amylacea formation, and stimulated prostatic gluthatione-S-transferase activity. In conclusion, MLT partially recovered prostate damage induced by aging and the long-term high-fat diet and ameliorated degenerative prostate alterations.

Tumor-Associated Macrophages (TAM) are recruited to the aging prostate epithelial lesions and become intermingled with basal cells

BACKGROUND

Prostate cancer remains one of the most common cancers in men. Macrophages are thought to be important regulators in cancers, and their potential involvement in prostate cancer should not be overlooked. Therefore, the association between macrophages and the pre-tumorous changes in prostate epithelium during aging deserves further investigation.

OBJECTIVES

We sought to investigate whether macrophages would be recruited into the prostate epithelium that display pathological lesions commonly found during aging.

MATERIALS AND METHODS

Prostates of aging rats, with and without treatment with a combination of testosterone and estradiol, were examined for premalignant and malignant epithelial lesions. For comparison, prostates of castrated rats were also investigated.

RESULTS

Intraepithelial macrophages were found restricted to areas of premalignant and malignant lesions. An unprecedented interaction between macrophages and basal cells was observed in the aging pathological lesions. The intraepithelial macrophages were associated with autophagy, in contrast to those found after castration. In prostate lesions, the intraepithelial macrophages had TAM phenotype (CD68+/iNOS+/CD206+/ARG+), denoting a possible involvement in cancer progression. However, M2 macrophages (CD68+/CD163+) were recruited into the epithelium after castration, possibly to phagocytize cells undergoing apoptosis.

DISCUSSION AND CONCLUSION

In conclusion, macrophages were recruited into the prostate epithelium and presented diverse phenotypes and morphology, consistent with changes reflected in the hormonal environment. Macrophages with the TAM phenotype were found restricted to areas of premalignant and malignant lesions in aging prostates, denoting a possible involvement in cancer progression. In contrast, M2 macrophages were found in the regressed epithelium after castration.