Radiation-induced abscopal reproductive effect is driven by TNF-α/p38 MAPK/Rac1 axis in Sertoli cells

SCF/C-kit drives spermatogenesis disorder induced by abscopal effects of cranial irradiation in mice

Cranial radiotherapy is a major treatment for leukemia and brain tumors. Our previous study found abscopal effects of cranial irradiation could cause spermatogenesis disorder in mice. However, the exact mechanisms are not yet fully understood. In the study, adult male C57BL/6 mice were administrated with 20 Gy X-ray cranial irradiation (5 Gy per day for 4 days consecutively) and sacrificed at 1, 2 and 4 weeks. Tandem Mass Tag (TMT) quantitative proteomics of testis was combined with bioinformatics analysis to identify key molecules and signal pathways related to spermatogenesis at 4 weeks after cranial irradiation. GO analysis showed that spermatogenesis was closely related to oxidative stress and inflammation. Severe oxidative stress occurred in testis, serum and brain, while serious inflammation also occurred in testis and serum. Additionally, the sex hormones related to hypothalamic-pituitary-gonadal (HPG) axis were disrupted. PI3K/Akt pathway was activated in testis, which upstream molecule SCF/C-Kit was significantly elevated. Furthermore, the proliferation and differentiation ability of spermatogonial stem cells (SSCs) were altered. These findings suggest that cranial irradiation can cause spermatogenesis disorder through brain-blood-testicular cascade oxidative stress, inflammation and the secretory dysfunction of HPG axis, and SCF/C-kit drive this process through activating PI3K/Akt pathway.

Inhibition of p38MAPK signalling pathway alleviates radiation-induced testicular damage through improving spermatogenesis

BACKGROUND AND PURPOSE

Damage to the testis following exposure to ionizing radiation has become an urgent problem to be solved. Here we have investigated if inhibition of p38 mitogen-activated protein kinase (p38MAPK) signalling could alleviate radiation-induced testicular damage.

EXPERIMENTAL APPROACH

In mice exposed to whole body radiation (2-6 Gy), morphological changes of the epididymis and testis was measured by histochemical staining. immunohistochemical and immunofluorescence procedures and western blotting were used to monitor expression and cellular location of proteins. Expression of genes was assessed by qPCR and RNA-Seq was used to profile gene expression.

KEY RESULTS

Exposure to ionizing radiation induced dose-dependent damage to mouse testis. The sperm quality decreased at 6 and 8 weeks after 6 Gy X-ray radiation. Radiation decreased PLZF+ cells and increased SOX9+ cells, and affected the expression of 969 genes, compared with data from non-irradiated mice. Expression of genes related to p38MAPK were enriched by GO analysis and were increased in the irradiated testis, and confirmed by qPCR. Levels of phospho-p38MAPK protein increased at 28 days after irradiation. In irradiated mice, SB203580 treatment increased spermatozoa, SOX9+ cells, the area and diameter of seminiferous tubules, sperm movement rate and density. Furthermore, SB203580 treatment increased SCP3+ cells, accelerating the process of spermatogenesis.

CONCLUSION AND IMPLICATIONS

Exposure to ionizing radiation clearly changed gene expression in mouse testis, involving activation of p38MAPK signalling pathways. Inhibition of p38MAPK by SB203580 partly alleviated the testicular damage caused by radiation and accelerated the recovery of sperms through promoting spermatogenesis.

Combined use of NK cells and radiotherapy in the treatment of solid tumors

Natural killer (NK) cells are innate lymphocytes possessing potent tumor surveillance and elimination activity. Increasing attention is being focused on the role of NK cells in integral antitumor strategies (especially immunotherapy). Of note, therapeutic efficacy is considerable dependent on two parameters: the infiltration and cytotoxicity of NK cells in tumor microenvironment (TME), both of which are impaired by several obstacles (e.g., chemokines, hypoxia). Strategies to overcome such barriers are needed. Radiotherapy is a conventional modality employed to cure solid tumors. Recent studies suggest that radiotherapy not only damages tumor cells directly, but also enhances tumor recognition by immune cells through altering molecular expression of tumor or immune cells via the in situ or abscopal effect. Thus, radiotherapy may rebuild a NK cells-favored TME, and thus provide a cost-effective approach to improve the infiltration of NK cells into solid tumors, as well as elevate immune-activity. Moreover, the radioresistance of tumor always hampers the response to radiotherapy. Noteworthy, the puissant cytotoxic activity of NK cells not only kills tumor cells directly, but also increases the response of tumors to radiation via activating several radiosensitization pathways. Herein, we review the mechanisms by which NK cells and radiotherapy mutually promote their killing function against solid malignancies. We also discuss potential strategies harnessing such features in combined anticancer care.

Organic anion transporting polypeptide 3a1 is a novel influx pump for Perfluorooctane sulfonate in Sertoli cells and contributes to its reproductive toxicity

Persistent organic pollutant perfluorooctane sulfonate (PFOS) is strongly associated with male reproductive disorders, but the related mechanisms are still not fully understood. In this study, we used in vivo and in vitro models to explore the role of organic anion transporting polypeptide 3a1 (Oatp3a1) on PFOS-induced male reproductive injury. Thirty male C57BL/6 (B6) mice were orally given PFOS (0-10 mg/kg/bw) for 28 days. Body weight, organ index, sperm count, histology, and blood-testis barrier (BTB) integrity were evaluated. Primary Sertoli cells were used to describe the related molecular mechanisms of male reproductive injury caused by PFOS. Our results showed that PFOS induced a decrease in sperm count, morphological damage to testicular Sertoli cells, and disruption of BTB. In the in vitro model, exposure to PFOS significantly increased Oatp3a1 mRNA and protein levels and decreased miR-23a-3p expression in Sertoli cells, accompanied by reduced trans-epithelial electrical resistance (TEER) value. By performing the 14C-PFOS uptake experiment, we showed that 14C-PFOS uptake in HEK293-Oatp3a1 cells was apparently higher than in HEK293-MOCK cells. Meanwhile, treating Sertoli cells with Oatp3a1 siRNA significantly decreased Oatp3a1 expression and rescued PFOS-induced decreases in TEER value. As such, the present study highlights that Oatp3a1 may play an important role in the toxic effect of PFOS on Sertoli cells, advancing our understanding of molecular mechanisms for PFOS-induced male reproductive disorders.

In Vitro and In Vivo Models for Drug Transport Across the Blood-Testis Barrier

The blood-testis barrier (BTB) is a selectively permeable membrane barrier formed by adjacent Sertoli cells (SCs) in the seminiferous tubules of the testes that develops intercellular junctional complexes to protect developing germ cells from external pressures. However, due to this inherent defense mechanism, the seminiferous tubule lumen can act as a pharmacological sanctuary site for latent viruses (e.g., Ebola, Zika) and cancers (e.g., leukemia). Therefore, it is critical to identify and evaluate BTB carrier-mediated drug delivery pathways to successfully treat these viruses and cancers. Many drugs are unable to effectively cross cell membranes without assistance from carrier proteins like transporters because they are large, polar, and often carry a charge at physiologic pH. SCs express transporters that selectively permit endogenous compounds, such as carnitine or nucleosides, across the BTB to support normal physiologic activity, although reproductive toxicants can also use these pathways, thereby circumventing the BTB. Certain xenobiotics, including select cancer therapeutics, antivirals, contraceptives, and environmental toxicants, are known to accumulate within the male genital tract and cause testicular toxicity; however, the transport pathways by which these compounds circumvent the BTB are largely unknown. Consequently, there is a need to identify the clinically relevant BTB transport pathways in in vitro and in vivo BTB models that recapitulate human pharmacokinetics and pharmacodynamics for these xenobiotics. This review summarizes the various in vitro and in vivo models of the BTB reported in the literature and highlights the strengths and weaknesses of certain models for drug disposition studies. SIGNIFICANCE STATEMENT: Drug disposition to the testes is influenced by the physical, physiological, and immunological components of the blood-testis barrier (BTB). But many compounds are known to cross the BTB by transporters, resulting in pharmacological and/or toxicological effects in the testes. Therefore, models that assess drug transport across the human BTB must adequately account for these confounding factors. This review identifies and discusses the benefits and limitations of various in vitro and in vivo BTB models for preclinical drug disposition studies.

m6A demethylase ALKBH5 attenuates doxorubicin-induced cardiotoxicity via posttranscriptional stabilization of Rasal3

The clinical application of anthracyclines such as doxorubicin (DOX) is limited due to their cardiotoxicity. N6-methyladenosine (m⁶A) plays an essential role in numerous biological processes. However, the roles of m⁶A and m⁶A demethylase ALKBH5 in DOX-induced cardiotoxicity (DIC) remain unclear. In this research, DIC models were constructed using Alkbh5-knockout (KO), Alkbh5-knockin (KI), and Alkbh5-myocardial-specific knockout (ALKBH5^{flox/flox, αMyHC-Cre}) mice. Cardiac function and DOX-mediated signal transduction were investigated. As a result, both Alkbh5 whole-body KO and myocardial-specific KO mice had increased mortality, decreased cardiac function, and aggravated DIC injury with severe myocardial mitochondrial damage. Conversely, ALKBH5 overexpression alleviated DOX-mediated mitochondrial injury, increased survival, and improved myocardial function. Mechanistically, ALKBH5 regulated the expression of Rasal3 in an m⁶A-dependent manner through posttranscriptional mRNA regulation and reduced Rasal3 mRNA stability, thus activating RAS3, inhibiting apoptosis through the RAS/RAF/ERK signaling pathway, and alleviating DIC injury. These findings indicate the potential therapeutic effect of ALKBH5 on DIC.

P38 MAPK and Radiotherapy: Foes or Friends?

Over the last 30 years, the study of the cellular response to ionizing radiation (IR) has increased exponentially. Among the various signaling pathways affected by IR, p38 MAPK has been shown to be activated both in vitro and in vivo, with involvement in key processes triggered by IR-mediated genotoxic insult, such as the cell cycle, apoptosis or senescence. However, we do not yet have a definitive clue about the role of p38 MAPK in terms of radioresistance/sensitivity and its potential use to improve current radiotherapy. In this review, we summarize the current knowledge on this family of MAPKs in response to IR as well as in different aspects related to radiotherapy, such as their role in the control of REDOX, fibrosis, and in the radiosensitizing effect of several compounds.

Golgi Phosphoprotein 3 Mediates Radiation-Induced Bystander Effect via ERK/EGR1/TNF-α Signal Axis

The radiation-induced bystander effect (RIBE), an important non-targeted effect of radiation, has been proposed to be associated with irradiation-caused secondary cancers and reproductive damage beyond the irradiation-treated area after radiotherapy. However, the mechanisms for RIBE signal(s) regulation and transduction are not well understood. In the present work, we found that a Golgi protein, GOLPH3, was involved in RIBE transduction. Knocking down GOLPH3 in irradiated cells blocked the generation of the RIBE, whereas re-expression of GOLPH3 in knockdown cells rescued the RIBE. Furthermore, TNF-α was identified as an important intercellular signal molecule in the GOLPH3-mediated RIBE. A novel signal axis, GOLPH3/ERK/EGR1, was discovered to modulate the transcription of TNF-α and determine the level of released TNF-α. Our findings provide new insights into the molecular mechanism of the RIBE and a potential target for RIBE modulation.

Antimicrobial peptide MPX attenuates LPS-induced inflammatory response and blood-testis barrier dysfunction in Sertoli cells

Orchitis accounts for a high proportion of male animal reproductive disorders. Hence, it is urgent to identify drugs for the prevention and treatment of orchitis. Antimicrobial peptides (AMPs) are currently recognized as one of the most promising alternatives to antibiotics. However, the protective effects of AMPs on lipopolysaccharide (LPS)-induced orchitis have not been reported. In this study, we developed an LPS-induced orchitis model in which primary bovine Sertoli cells were used as model cells. MPX was indicated to effectively reduce the inflammatory response of Sertoli cells. MPX attenuated the gene expression of the proinflammatory cytokines TNF-α, IL-6 and IL-1β by suppressing the MAPK pathway, especially the phosphorylation of p38 and ERK. MPX also decreased the oxidative stress response caused by LPS and upregulated Occludin and Claudin-1 expression, thereby maintaining the integrity of the blood-testis barrier. Moreover, we found that MPX inhibited apoptosis in Sertoli cells. In a mouse model, we found that MPX significantly inhibited the disruptive effects of LPS, reducing seminiferous epithelium damage, vacuolations, hyperplasia, and apoptosis in spermatogenic cells and rescuing spermatogenesis. In addition, the expression of inflammatory factors such as IL-1β, IL-18, IL-6 and TNF-α was decreased after MPX treatment in the mouse testes. MPX had no effect on other organs in mice, indicating its safety. This study was undertaken to investigate how MPX regulates the inflammatory response in Sertoli cells and provide a reference for the clinical prevention and treatment of male animal orchitis.

Glyphosate damages blood-testis barrier via NOX1-triggered oxidative stress in rats: Long-term exposure as a potential risk for male reproductive health

Blood-testis barrier (BTB) creates a privileged niche indispensable for spermatogenesis. Glyphosate (GLY), the most commonly used herbicide worldwide, has been reported to decrease sperm quality. However, whether and how GLY destroys the BTB to affect sperm quality remains to be elucidated. Herein, this study was designed to investigate the influence of GLY on the BTB in vivo and in vitro experiments. The results showed that male rats exposed to GLY for 4 months exhibited a decrease in sperm quality and quantity, accompanied by BTB integrity disruption and testicular oxidative stress. Additionally, GLY-induced reactive oxygen species (ROS) contributed to the downregulation of BTB-related proteins in primary Sertoli cells (SCs). Intriguingly, we identified a marked upregulation of oxidative stress-related gene NOX1 in GLY-exposed testis based on transcriptome analysis. NOX1 knockdown blocked the GLY-induced oxidative stress, as well as prevented BTB-related protein decrease in SCs. Furthermore, the estrogen receptor (ER)-α was significantly upregulated in vivo and in vitro models. An ER-α inhibitor decreased the expression levels of both ER-α and NOX1. Mechanistically, GLY directly interacted with ER-α at the site of Pro39 and Lys401 to promote ER-α activation, which boosted NOX1 expression to trigger ROS accumulation. Collectively, these results demonstrate that long-term GLY exposure adversely affects BTB integrity, which disrupts spermatogenesis via activation of ER-α/NOX1 axis. This study presents a better understanding of the risk of long-term GLY exposure to male fertility.

Fractionated Irradiation of Right Thorax Induces Abscopal Damage on Bone Marrow Cells via TNF-α and SAA

Radiation-induced abscopal effect (RIAE) outside of radiation field is becoming more attractive. However, the underlying mechanisms are still obscure. This work investigated the deleterious effect of thoracic irradiation (Th-IR) on distant bone marrow and associated signaling factors by irradiating the right thorax of mice with fractionated doses (8 Gy × 3). It was found that this localized Th-IR increased apoptosis of bone marrow cells and micronucleus formation of bone marrow polychromatic erythrocytes after irradiation. Tandem mass tagging (TMT) analysis and ELISA assay showed that the concentrations of TNF-α and serum amyloid A (SAA) in the mice were significantly increased after Th-IR. An immunohistochemistry assay revealed a robust increase in SAA expression in the liver rather than in the lungs after Th-IR. In vitro experiments demonstrated that TNF-α induced SAA expression in mouse hepatoma Hepa1-6 cells, and these two signaling factors induced DNA damage in bone marrow mesenchymal stem cells (BMSCs) by increasing reactive oxygen species (ROS). On the other hand, injection with TNF-α inhibitor before Th-IR reduced the secretion of SAA and attenuated the abscopal damage in bone marrow. ROS scavenger NAC could also mitigated Th-IR/SAA-induced bone marrow damage in mice. Our findings indicated that Th-IR triggered TNF-α release from lung, which further promoted SAA secretion from liver in a manner of cascade reaction. Consequently, these signaling factors resulted in induction of abscopal damage on bone marrow of mice.