Dexamethasone acutely regulates endocrine parameters in stallions and subsequently affects gene expression in testicular germ cells

Physiological roles of propolis and red ginseng nanoplatforms in alleviating dexamethasone-induced male reproductive challenges in a rat model

BACKGROUND

Red ginseng and propolis are well-known antioxidants that have been related to a reduction in oxidative stress.

OBJECTIVE

This study evaluated the efficiency of red ginseng and propolis, either in powder or as nano-forms against dexamethasone-induced testicular oxidative challenges in adult male albino rats.

METHODS

Forty rats were divided into 8 equal groups including control negative group that was given vehicle (DMSO), control positive group that was administered dexamethasone in addition to the nano-propolis, nano-ginseng, nano-propolis + dexamethasone, nano ginseng+dexamethasone, propolis+dexamethasone and ginseng + dexamethasone groups. Serum, semen and tissue samples were obtained.

RESULTS

Lower testosterone levels, higher levels of MDA, and lower levels of total antioxidant capacity in serum, as well as impaired semen quality and a disturbed histopathological picture of both the testis and seminal glands, were all observed as significant negative effects of dexamethasone. These findings were confirmed by lower gene expression profiles of CYP11A1, StAR, HSD-3b, Nrf-2 and ACTB-3b in testicular and seminal gland tissues. The most powerful anti-dexamethasone effects were obtained with either propolis in nanoform or conventional ginseng.

CONCLUSION

Propolis nano-formulation and ginseng in conventional form could be considered excellent candidates to ameliorate the oxidative stress provoked by dexamethasone, however, neither nano-ginseng nor conventional propolis showed such effects.

Conservation of Glutathione Transferase mRNA and Protein Sequences Similar to Human and Horse Alpha Class GST A3-3 across Dog, Goat, and Opossum Species

The glutathione transferase A3-3 (GST A3-3) homodimeric enzyme is the most efficient enzyme that catalyzes isomerization of the precursors of testosterone, estradiol, and progesterone in the gonads of humans and horses. However, the presence of GST A3-3 orthologs with equally high ketosteroid isomerase activity has not been verified in other mammalian species, even though pig and cattle homologs have been cloned and studied. Identifying GSTA3 genes is a challenge because of multiple GSTA gene duplications (e.g., 12 in the human genome); consequently, the GSTA3 gene is not annotated in most genomes. To improve our understanding of GSTA3 gene products and their functions across diverse mammalian species, we cloned homologs of the horse and human GSTA3 mRNAs from the testes of a dog, goat, and gray short-tailed opossum, the genomes of which all currently lack GSTA3 gene annotations. The resultant novel GSTA3 mRNA and inferred protein sequences had a high level of conservation with human GSTA3 mRNA and protein sequences (≥70% and ≥64% identities, respectively). Sequence conservation was also apparent for the 12 residues of the "H-site" in the 222 amino acid GSTA3 protein that is known to interact with the steroid substrates. Modeling predicted that the dog GSTA3-3 may be a more active ketosteroid isomerase than the corresponding goat or opossum enzymes. However, expression of the GSTA3 gene was higher in liver than in other dog tissue. Our results improve understanding of the active sites of mammalian GST A3-3 enzymes, inhibitors of which might be useful for reducing steroidogenesis for medical purposes, such as fertility control or treatment of steroid-dependent diseases.

Pathogenesis of the crosstalk between reproductive function and stress in animals-part 1: Hypothalamo-pituitary-adrenal axis, sympatho-adrenomedullary system and kisspeptin

Stress is defined as a disruption of the body homeostasis in response to modest as well as perceived challenge. Two main physiological routes, the hypothalamic-pituitary-adrenal system (HPA) and the sympatho-adrenomedullary system (SAM), aim to maintain or restore homeostasis by mutual interaction. SAM is quickly-reacting as it primarily works through the nervous system-the sympathetic nervous system. In response to stress, signals are sent to activate the adrenal medulla which releases catecholamines (primarily adrenaline and norepinephrine). The catecholamines have a momentary effect on the body's organs that are prepared for a fight situation. At the same time, the stressor activates the HPA axis by signals from the brain causing secretion of the pituitary hormone adrenocorticotropic hormone (ACTH). ACTH acts on the adrenal cortex, which secretes glucocorticoids, including cortisol. Since HPA primarily works through hormones, the system is slightly slower than SAM and gives rise to a metabolic effect. While short-term stress response is an adaptive and beneficial process, chronic or excessive stress can lead to a range of negative health outcomes including reproductive disorders and infertility. Several mechanisms have been proposed to explain the link between stress and reproduction. This includes in particular kisspeptin, which is closely related to reproduction, as it is a powerful stimulator of the Hypothalamic-pituitary-gonadal (HPG) system. The present review, through current knowledge in various male and female species, deals with the role of the SAM and the HPA, including the major action of kisspeptin and glucocorticoids that trigger the consequences of psychological or physiological stress on reproductive function.

Dexamethasone downregulates expression of several genes encoding orphan nuclear receptors that are important to steroidogenesis in stallion testes

Glucocorticoids impair testosterone synthesis by an unknown mechanism. Stallions treated with the synthetic glucocorticoid dexamethasone had testes collected at 6 or 12 hours postinjection. The testicular expression of selected genes encoding nuclear receptors and steroidogenic enzymes was measured. At 6 hours, dexamethasone treatment decreased levels of NR0B2, NR4A1, NR5A1, and NR5A2 messenger RNAs (mRNAs) and NR5A2 mRNA levels remained depressed at 12 hours. In contrast, dexamethasone increased levels of NFKBIA mRNA at both time points. At 6 hours, dexamethasone did not alter levels of NR0B1, NR2F1, NR2F2, NR3C1, CYP11A1, CYP17A1, CYP19A1, DHCR24, GSTA3, HSD3B2, HSD17B3, LHCGR, or STAR mRNAs. In primary cultures of Leydig cells, 10 ^-9 and 10 ^-7 M dexamethasone decreased levels of NR4A1 and NR5A1 mRNAs and increased those of NFKBIA mRNA. Our discovery that dexamethasone downregulates NR4A1, NR5A1, and NR5A2 genes, known to be important for testicular functions, may be part of the mechanism by which glucocorticoids acutely decreases testosterone.

Immunosuppressants and Male Reproduction

Prolonged use of immunosuppressant medications is occasionally seen in infertile men with chronic inflammatory conditions; autoimmune disorders; or an organ or hematopoietic stem cell transplant. Chronic inflammation impacts negatively on male reproductive endpoints, so immunosuppressant therapy can produce improvements. Corticosteroids have been used to treat antisperm antibodies and even as an empirical treatment for male infertility in general. Trials of these methods have provided mixed results on semen quality and fertility, with improvement, no change and negative effects reported by different investigators. In a substantial number of observational studies, patients on long-term therapy with prednisone for chronic inflammatory disease, testosterone levels were lower compared to untreated controls, though randomized controlled trials have not been conducted. Similarly decreases in testosterone have been reported in men receiving corticosteroids to minimize transplant rejection; however, most were treated with multiple immunosuppressive medications that may have contributed to this effect. A large number of trials of healthy men treated with corticosteroids have shown some disruption in reproductive hormone levels, but other studies reported no effect. Studies in monkeys, rats (at human equivalent dose), cattle, sheep, and horses have shown endocrine disruption, including low testosterone with dexamethasone treatment. Of the cytostatic immunosuppressives, which have high potential for cellular damage, cyclophosphamide has received the most attention, sometimes lowering sperm counts significantly. Methotrexate may decrease sperm numbers in humans and has significant negative impacts in rodents. Other chemotherapeutic drugs used as immunosuppressants are likely to impact negatively on male fertility endpoints, but few data have been collected. The TNF-α Inhibitors have also received little experimental attention. There is some evidence that the immunophilin modulators: cyclosporine, sirolimus, and everolimus cause endocrine disruption and semen quality impairment. As we review in this chapter, results in experimental species are concerning, and well-designed studies are lacking for the effects of these medications on reproductive endpoints in men.