Effects of photoperiod on morphology and function in testis and epididymis of Cricetulus barabensis

The neurobiological mechanisms of photoperiod impact on brain functions: a comprehensive review

Variations in day length, or photoperiodism, whether natural or artificial light, significantly impact biological, physiological, and behavioral processes within the brain. Both natural and artificial light sources are environmental factors that significantly influence brain functions and mental well-being. Photoperiodism is a phenomenon, occurring either over a 24 h cycle or seasonally and denotes all biological responses of humans and animals to these fluctuations in day and night length. Conversely, artificial light occurrence refers to the presence of light during nighttime hours and/or its absence during the daytime (unnaturally long and short days, respectively). Light at night, which is a form of light pollution, is prevalent in many societies, especially common in certain emergency occupations. Moreover, individuals with certain mental disorders, such as depression, often exhibit a preference for darkness over daytime light. Nevertheless, disturbances in light patterns can have negative consequences, impacting brain performance through similar mechanisms albeit with varying degrees of severity. Furthermore, changes in day length lead to alterations in the activity of receptors, proteins, ion channels, and molecular signaling pathways, all of which can impact brain health. This review aims to summarize the mechanisms by which day length influences brain functions through neural circuits, hormonal systems, neurochemical processes, cellular activity, and even molecular signaling pathways.

Expression and localization of Cyclin D1/Nanog and NF-κB/Bax protein in dysplastic testicles of mice

Testicular dysplasia significantly impairs male reproductive capacity. This study investigated the expression of Cyclin D1/Nanog and NF-κB/Bax in dysplastic testes of mice using histological staining, Western blotting, and immunohistochemistry. The results showed that Nanog and Bax expression were significantly higher in dysplastic testicular tissue than in normal tissue (P < 0.01). Cyclin D1 protein expression was higher in normal testis tissue than in dysplastic testis (P < 0.01). NF-κB was highly expressed in cryptorchid and normal testis with no significant difference (P > 0.05). Immunolocalization revealed that Nanog, NF-κB, and Bax were expressed in the cytoplasm of Leydig and spermatogenic cells. Cyclin D1 primarily expressed in the nucleus of Sertoli cells. These findings suggest that altered expression of Nanog, Cyclin D1, and Bax may contribute to testicular dysplasia. This study provides a scientific foundation for detecting testicular dysplasia and selecting appropriate animal models, ultimately informing strategies to improve male reproductive health.

Photoperiod-regulated mitophagy in the germ cells of Brandt's voles (Lasiopodomys brandtii)

Photoperiod is a pivotal factor in affecting testicular function and spermatogenesis in seasonal-breeding animals. Mitophagy is essential for spermatogenesis, but its association with seasonal photoperiods has not been studied extensively. To explore this, we exposed male Brandt's voles (Lasiopodomys brandtii) to long-photoperiod (LP, 16 h/day) and short-photoperiod (SP, 8 h/day) conditions from their embryonic stages. Our results indicated that testis weight, volume, and relative testes weight were all significantly increased in LP compared to SP. Additionally, blood testosterone levels were markedly higher in LP than SP. Histological examination revealed that seminiferous diameter and epithelium thickness were greater in LP, with an increased abundance of germ cell types and cell numbers compared to SP. RT-qPCR analysis showed that mitophagy-promoting genes, such as Pink1, Prkn, Tomm7, Mnf2, Lc3, Optn, Gabarap, and Nbr1 were all upregulated in LP. Fluorescence in situ hybridization indicated that Pink1 expression was present in spermatogonia in SP, while in LP, Pink1 expression extended to almost all germ cell types with significantly higher mean optical density. Prkn expression was found in all germ cell types in both LP and SP, with a significantly higher mean optical density of 10-week-old LP males. Transmission electron microscopy showed normal mitochondrial morphology with clear membranes in SP, while the LP group had reduced cristae in mitochondria and damaged mitochondria undergoing autophagy. This study suggests that mitophagy may be involved in the photoperiodic spermatogenesis in Brandt's voles, providing insights into the role of photoperiod in seasonal reproduction in wild animals.

Small RNA-seq and hormones in the testes of dwarf hamsters (Cricetulus barabensis) reveal the potential pathways in photoperiod regulated reproduction

Photoperiod regulates the functions and development of gonadal organs of seasonally breeding animals, resulting in breeding peaks in specific seasons. miRNA plays an important role in the regulation of testicular physiological functions. However, the relationship between photoperiods and miRNA levels in testes has yet to be conclusively determined. We investigated testicular miRNA of striped dwarf hamster (Cricetulus barabensis) responses to different photoperiods (long daylength [LD], moderate daylength [MD], and short daylength [SD]) and the potential pathways involved in photoperiod regulated reproduction. Testicular weights and reproductive hormone levels were measured in each of photoperiod treatments after 30 days. The concentrations of testosterone (T) and dihydrogen testosterone (DHT) in testes and Gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) in serum were higher in MD than in the other two groups. Testicular weights were heaviest in MD. Small RNA-seq was performed for the testes of hamsters in three groups. A total of 769 miRNAs were identified, of which 83 were differentially expressed between LD, MD, and SD. GO and KEGG analysis of target genes revealed that some miRNAs influence testicular activities by regulating the pathways related to cell apoptosis and metabolism. Gene expression pattern analysis showed that the MAPK signaling pathway may be the core pathway for photoperiodic regulation of reproduction. These results suggest that moderate daylength is more suitable for hamster reproduction while long daylength and short daylength may regulate reproduction through different molecular pathways.

Photoperiodic-dependent histomorphological changes in the excurrent duct system of helmeted guinea fowl subjected to short day (8L:16D), long-day (16L:8D) light/dark cycles and exogenous melatonin

In the present study, the influence of varying photoperiods [short day light 8L:16D, long day light 16L;8D] and exogeneous melatonin on the excurrent duct system of male helmeted guinea fowl was investigated using histo-morphological and histometric approaches. A total of twenty-eight (28) guinea fowl birds were randomly divided into Group I: Short daylight (SD; 8 HL), Group II: (SD +1mg/kg melatonin; 8 HL+ Mel), Group III: Long daylight (LD; 16 HL) and Group IV: (LD +1mg/kg; 16 HL + Mel)] and comprises of seven birds (n=7) per group. At the end of the 8 weeks of experimentation, the excurrent ducts were excised and processed for routine histological examination and the variations in histo-morphometrical parameters were determined using the GIMP2 software. Histologically, apart from the moderate cellular degeneration observed in efferent duct epithelia of the SD subgroups: (8 HL and 8 HL + Mel), there was remarkable spermatozoa presence in the lumens of the epididymal duct and ductus deferens of both 16 HL and 16 HL + Mel groups. The histo-morphometric data (luminal, ductal diameters and epithelial heights) were significantly increased (p <0.05) in the excurrent ducts of guinea fowl exposed to 16 HL and 16 HL + Mel, as compared to other groups. There was significant decrease (p <0.05) in stereocilia height (SH) in 16 HL compared to 8 HL sub-groups of lower segments. Although, a non-significant (p >0.05) increase in SH was observed in melatonin-treated groups, regardless of photoperiod. Taken together, these sets of data from this study indicate the importance of artificial light and exogenous melatonin in the control of seasonality of reproduction and which could be used to influence the reproductive cycle of the guinea fowl.

Effect of seasons and photoperiods on seminal attributes and sperm morphology in Holstein Friesian × Sahiwal crossbred dairy bulls

Cattle being non-seasonal breeding species, effects of photoperiods on sperm traits and morphology had been reported inadequately in breeding bulls. To elucidate the plausible existence of effects of photoperiods and seasons, seminal traits of Holstein Friesian × Sahiwal crossbred dairy bulls (N = 557) were analysed using different statistical models. A present study revealed that the biological rhythm of reproduction oscillated almost in parallel to the annual changes of natural photoperiods even in non-seasonal breeding species like cattle bulls. Semen traits diminished to the lowest in winter solstice (WS ± 45 days), progressively increased with the rising day length of spring (vernal equinox ± 45 days), reached a peak in summer solstice (SS ± 45 days), and then gradually reduced with decreasing photoperiod of the autumn equinox (AE ± 45 days). From summer solstice to winter solstice, sperm concentration reduced by 90.53 million/ml (8.85%), total sperm count/ejaculate decreased by 785 million (13.87%), total motile sperm count/ejaculate reduced by 17.59%, and total post-thaw motile sperm counts/ejaculates diminished by 38.64%. In short-duration photoperiods (≤ 12 h), bulls had a significantly (P < 0.01) higher incidence of major, minor, tail abnormality and total aberrant sperm% compared to that of long-duration photoperiods (> 12 h). Solstice equinox-based seasonal classification provided better insight into photoperiodicity on bulls' semen quality and sperm traits as compared to conventional meteorological classification of seasons. It was concluded that photoperiods affect sperm productivity, semen quality, and sperm morphology in non-seasonal breeding species like dairy bulls, maintained at transitional latitude (29° N) tropical climate. Bulls' reproductive ability was more influenced by the phases of increasing/decreasing day length duly primed by climax/trough of photoperiods, compared to mere long/short duration of photoperiods.

Prolonging photoperiod promotes testosterone synthesis of Leydig cells by directly targeting local melatonin system in rooster testes

The study investigated the effects of prolonging photoperiod on the synthesis of testosterone and melatonin in roosters, and the effect of melatonin on testosterone synthesis in rooster Leydig cells as well as its molecular mechanisms. We randomly divided one hundred and twenty 20-week-old roosters into three groups and provided 6, 12.5 and 16 h light, respectively. The results showed that prolonging photoperiod promoted testosterone synthesis, decreased melatonin production, and inhibited the expression of melatonin membrane receptors MEL1A, MEL1B, MEL1C, and aralkylamine n-acetyltransferase (AANAT) in rooster testes. Subsequently, rooster Leydig cells were isolated and treated with 0, 0.1, 1, 10, and 100 ng/mL melatonin for 36 h. The results suggested that melatonin inhibited testosterone synthesis in rooster Leydig cells, and silencing MEL1A and MEL1B relieved the inhibition of melatonin on testosterone synthesis. Additionally, melatonin reduced the intracellular cyclic adenosine monophosphate (cAMP) level and the phosphorylation level of cAMP-response element binding protein (CREB), and CREB overexpression alleviated the inhibition of melatonin on testosterone synthesis. Furthermore, pretreatment with cAMP activator forskolin or protein kinase A (PKA) activator 8-bromo-cAMP blocked the inhibition of melatonin on CREB phosphorylation and testosterone synthesis. These results indicated that prolonging photoperiod promoted testosterone synthesis associated with the decrease in melatonin production and membrane receptors and biosynthetic enzyme of melatonin in rooster testes, and melatonin inhibited testosterone synthesis of rooster Leydig cells by inhibiting the cAMP/PKA/CREB pathway via MEL1A and MEL1B. This may be evidence that prolonging photoperiod could promote testosterone synthesis through the inhibition of the local melatonin pathway in rooster testes.

Zika virus disrupts the barrier structure and Absorption/Secretion functions of the epididymis in mice

Several studies have demonstrated that Zika virus (ZIKV) damages testis and leads to infertility in mice; however, the infection in the epididymis, another important organ of male reproductive health, has gained less attention. Previously, we detected lesions in the epididymis in interferon type I and II receptor knockout male mice during ZIKV infection. Herein, the pathogenesis of ZIKV in the epididymis was further assessed in the infected mice after footpad inoculation. ZIKV efficiently replicated in the epididymis, and principal cells were susceptible to ZIKV. ZIKV infection disrupted the histomorphology of the epididymis, and the effects were characterized by a decrease in the thickness of the epithelial layer and an increase in the luminal diameter, especially at the proximal end. Significant inflammatory cell infiltration was observed in the epididymis accompanied by an increase in the levels of interleukin (IL)-6 and IL-28. The expression of tight junction proteins was downregulated and associated with disordered arrangement of the junctions. Importantly, the expression levels of aquaporin 1 and lipocalin 8, indicators of the absorption and secretion functions of the epididymis, were markedly reduced, and the proteins were redistributed. These events synergistically altered the microenvironment for sperm maturation, disturbed sperm transport downstream, and may impact male reproductive health. Overall, these results provide new insights into the pathogenesis of the male reproductive damage caused by ZIKV infection and the possible contribution of epididymal injury into this process. Therefore, male fertility of the population in areas of ZIKV epidemic requires additional attention.

Unlike other mosquito-transmitted flaviviruses, ZIKV can persistently replicate in the male reproductive system and is sexually transmitted. ZIKV infection was reported to damage testis. However, ZIKV-induced epididymal injury was not investigated in detail. Clinically, epididymitis is closely associated with male infertility. In this study, a mouse model was used to demonstrate that ZIKV causes histomorphological and functional changes in the epididymis, which may alter the microenvironment of sperm maturation and movement and finally lead to male infertility. Therefore, long-term investigation of male reproductive health may be needed in the areas of ZIKV epidemic.