MAPKAP kinase 2-mediated phosphorylation of HspA1L protects male germ cells from heat stress-induced apoptosis

Heat stress induces ferroptosis of porcine Sertoli cells by enhancing CYP2C9-Ras- JNK axis

Heat stress leads to the accumulation of lipid peroxides in Sertoli cells. Unrestricted lipid peroxidation of catalyzed polyunsaturated fatty acids by Cytochrome P450 (CYP) drive the ferroptosis. However, little is known about the role of CYP cyclooxygenase in heat stress-induced ferroptosis in Sertoli cells. In this study, we investigated the relationship between CYP cyclooxygenase and heat stress-induced ferroptosis in porcine Sertoli cells, as well as whether Ras-JNK signaling is involved in the process. The results showed that heat stress significantly increased the expression of cytochrome P450 cyclooxygenase 2C9 (CYP2C9) and the content of epoxyeicosatrienoic acids (EETs), although there are no significant effect on the expression of cytochrome P450 cyclooxygenase 2J2 (CYP2J2) and cytochrome P450 cyclooxygenase 2C8 (CYP2C8). In addition, heat stress reduced the cell viability, the protein expression level of glutathione peroxidase 4 (GPX4) and Ferritin (all P < 0.01) while increased the level of intracellular reactive oxygen species (ROS) and the protein level of Transferrin receptor 1(TFR1) (both P < 0.01), as well as activating the Ras-JNK signaling pathway. Ferrostatin-1, a ferroptosis-specific inhibitor, reduced ROS levels and the protein level of TFR1 (both P < 0.01), but elevated the cell viability, the protein level of GPX4, and Ferritin (all P < 0.01). Sulfaphenazole, a specific inhibitor of CYP2C9 or two small interfering RNAs targaring CYP2C9 enhanced the cell viability (all P < 0.01), while reduced the content of EETs (all P < 0.01) and inhibited the Ras-JNK signaling and ferroptosis under heat stress. Salirasib, a specific inhibitor of Ras, significantly elevated the cell viability, whereas reduced the level of intracellular ROS and inhibited the phosphorylation of JNK, and alleviated heat stress-induced ferroptosis in porcine Sertoli cells. Notably, there is no effect on the expression of CYP2C9 and the content of EETs. These results indicate that heat stress can induce ferroptosis in Sertoli cells by increasing the expression of CYP2C9 and the content of EETs, which in true activates the Ras-JNK signaling pathway, but there is no feedback from Ras-JNK signaling to the expression of CYP2C9. Our study finds a novel heat stress-induced cell death model of Sertoli cells as well as providing the therapeutic potential for anti-ferroptosis.

Heat wave exposure and semen quality in sperm donation volunteers: A retrospective longitudinal study in south China

BACKGROUND

Previous studies have suggested an association between non-optimum ambient temperature and decreased semen quality. However, the effect of exposure to heat waves on semen quality remains unclear.

METHODS

Volunteers who intended to donate sperm in Guangdong provincial human sperm bank enrolled. Heat waves were defined by temperature threshold and duration, with a total of 9 definitions were employed, specifying daily mean temperature exceeding the 85th, 90th, or 95th percentile for at least 2, 3, or 4 consecutive days. Residential exposure to heat waves during 0-90 days before ejaculation was evaluated using a validated gridded dataset on ambient temperature. Association and potential windows of susceptibility were evaluated and identified using linear mixed models and distributed lag non-linear models.

RESULTS

A total of 2183 sperm donation volunteers underwent 8632 semen analyses from 2018 to 2019. Exposure to heat wave defined as daily mean temperature exceeding the 95th percentile for at least 4 consecutive days (P95-D4) was significantly associated with a 0.11 (95% confidence interval [CI]: 0.03, 0.18) ml, 3.36 (1.35, 5.38) × 106/ml, 16.93 (7.95, 25.91) × 106, and 2.11% (1.4%, 2.83%) reduction in semen volume, sperm concentration, total sperm number, and normal forms, respectively; whereas exposure to heat wave defined as P90-D4 was significantly associated with a 1.98% (1.47%, 2.48%) and 2.08% (1.57%, 2.58%) reduction in total motility and progressive motility, respectively. Sperm count and morphology were susceptible to heat wave exposure during the early stage of spermatogenesis, while sperm motility was susceptible to exposure during the late stage.

CONCLUSION

Heat wave exposure was significantly associated with a reduction in semen quality. The windows of susceptibility during 0-90 days before ejaculation varied across sperm count, motility, and morphology. Our findings suggest that reducing heat wave exposure before ejaculation may benefit sperm donation volunteers and those attempting to conceive.

GGA1 participates in spermatogenesis in mice under stress

BACKGROUND

Infertility is recognized as a common and worrisome problem of human reproduction worldwide. Based on previous studies, male factors account for about half of all infertility cases. Exposure to environmental toxicants is an important contributor to male infertility. Bisphenol A (BPA) is the most prominent toxic environmental contaminant worldwide affecting the male reproductive system. BPA can impair the function of the Golgi apparatus which is important in spermatogenesis. GGA1 is known as Golgi-localized, gamma adaptin ear-containing, ARF-binding protein 1. Previously, it has been shown that GGA1 is associated with spermatogenesis in Drosophila, however, its function in mammalian spermatogenesis remains unclear.

METHODS

Gga1 knockout mice were generated using the CRISPR/Cas9 system. Gga1-/- male mice and wild-type littermates received intraperitoneal (i.p.) injections of BPA (40 µg/kg) once daily for 2 weeks. Histological and immunofluorescence staining were performed to analyze the phenotypes of these mice.

RESULTS

Male mice lacking Gga1 had normal fertility without any obvious defects in spermatogenesis, sperm count and sperm morphology. Gga1 ablation led to infertility in male mice exposed to BPA, along with a significant reduction in sperm count, sperm motility and the percentage of normal sperm. Histological analysis of the seminiferous epithelium showed that spermatogenesis was severely disorganized, while apoptotic germ cells were significantly increased in the Gga1 null mice exposed to BPA. Our findings suggest that Gga1 protects spermatogenesis against damage induced by environmental pollutants.

Role of p38 MAPK Signalling in Testis Development and Male Fertility

The testis is an important male reproductive organ, which ensures reproductive function via the secretion of testosterone and the generation of spermatozoa. Testis development begins in the embryonic period, continues after birth, and generally reaches functional maturation at puberty. The stress-activated kinase, p38 mitogen-activated protein kinase (MAPK), regulates multiple cell processes including proliferation, differentiation, apoptosis, and cellular stress responses. p38 MAPK signalling plays a crucial role in testis development by regulating spermatogenesis, the fate determination of pre-Sertoli, and primordial germ cells during embryogenesis, the proliferation of testicular cells in the postnatal period, and the functions of mature Sertoli and Leydig cells. In addition, p38 MAPK signalling is involved in decreased male fertility when exposed to various harmful stimuli. This review will describe in detail the biological functions of p38 MAPK signalling in testis development and male reproduction, together with its pathological role in male infertility.

Expressions of HSPA1L and HSPA9 are associated with poor sperm quality of low-motility spermatozoa in fertile men

Human semen is a heterogeneous group containing a portion of low-motility sperm, which may determine the sperm quality evaluation. Abnormally expressed proteins in low-motility spermatozoa will be the candidates for sperm biology research. By comparing proteomes of high- or low-motility spermatozoa from the same semen of normal fertile men, 21 differentially expressed proteins were identified. Proteins with molecular chaperone function were significantly over-represented, of which HSPA1L and HSPA9 significantly decreased in low-motility sperm. Compared with young adult testes with normal spermatogenesis, HSPA1L and HSPA9 had decreased expressions in elderly testis characterised with poor spermatogenesis, suggesting their associations with spermatogenesis. Decreased expressions of HSPA1L and HSPA9 in low-motility spermatozoa were validated by Western Blot and immunofluorescence quantification analysis. HSPA1L was mainly expressed on sperm post-acrosome and midpiece, whilst HSAP9 was mainly expressed on acrosome and sperm tail. HSPA1L antibody could inhibit sperm motility validated by antibody blocking experiment, whilst HSPA9 antibody showed no significant effect on sperm motility. The study demonstrated that low-motility spermatozoa from fertile men had poor sperm quality, in which differential expressed proteins were promising markers for evaluating sperm quality, understanding mechanism of male infertility with unexplained causes, and providing new idea for male infertility research.

Responses and coping methods of different testicular cell types to heat stress: overview and perspectives

To facilitate temperature adjustments, the testicles are located outside the body cavity. In most mammals, the temperature of the testes is lower than the body temperature to ensure the normal progression of spermatogenesis. Rising temperatures affect spermatogenesis and eventually lead to a decline in male fertility or even infertility. However, the testes are composed of different cell types, including spermatogonial stem cells (SSCs), spermatocytes, spermatozoa, Leydig cells, and Sertoli cells, which have different cellular responses to heat stress. Recent studies have shown that using different drugs can relieve heat stress-induced reproductive damage by regulating different signaling pathways. Here, we review the mechanisms by which heat stress damages different cells in testes and possible treatments.

HSPA1L Enhances Cancer Stem Cell-Like Properties by Activating IGF1Rβ and Regulating β-Catenin Transcription

Studies have shown that cancer stem cells (CSCs) are involved in resistance and metastasis of cancer; thus, therapies targeting CSCs have been proposed. Here, we report that heat shock 70-kDa protein 1-like (HSPA1L) is partly involved in enhancing epithelial–mesenchymal transition (EMT) and CSC-like properties in non-small cell lung cancer (NSCLC) cells. Aldehyde dehydrogenase 1 (ALDH1) is considered a CSC marker in some lung cancers. Here, we analyzed transcriptional changes in genes between ALDH1high and ALDH1low cells sorted from A549 NSCLC cells and found that HSPA1L was highly expressed in ALDH1high cells. HSPA1L played two important roles in enhancing CSC-like properties. First, HSPA1L interacts directly with IGF1Rβ and integrin αV to form a triple complex that is involved in IGF1Rβ activation. HSPA1L/integrin αV complex-associated IGF1Rβ activation intensified the EMT-associated cancer stemness and γ-radiation resistance through its downstream AKT/NF-κB or AKT/GSK3β/β-catenin activation pathway. Secondly, HSPA1L was also present in the nucleus and could bind directly to the promoter region of β-catenin to function as a transcription activator of β-catenin, an important signaling protein characterizing CSCs by regulating ALDH1 expression. HSPA1L may be a novel potential target for cancer treatment because it both enhances IGF1Rβ activation and regulates γβ-catenin transcription, accumulating CSC-like properties.