Cadmium is one of the environmental and occupational pollutants and its potential adverse effects on human health have given rise to substantial concern. Cadmium causes damage to the male reproductive system via induction of germ-cell apoptosis; however, the underlying mechanism of cadmium-induced reproductive toxicity in Leydig cells remains unclear. In this study, twenty mice were divided randomly into four groups and exposed to CdCl₂ at concentrations of 0, 0.5, 1.0 and 2.0 mg/kg/day for four consecutive weeks. Testicular injury, abnormal spermatogenesis and apoptosis of Leydig cells were observed in mice. In order to investigate the mechanism of cadmium-induced apoptosis of Leydig cells, a model of mouse Leydig cell line (i.e. TM3 cells) was subjected to treatment with various concentrations of CdCl₂. It was found that mitochondrial function was disrupted by cadmium, which also caused a significant elevation in levels of mitochondrial superoxide and cellular ROS. Furthermore, while cadmium increased the expression of mitochondrial fission proteins (DRP1 and FIS1), it reduced the expression of mitochondrial fusion proteins (OPA1 and MFN1). This led to excessive mitochondrial fission, the release of cytochrome c and apoptosis. Conversely, cadmium-induced accumulation of mitochondrial superoxide was decreased by the inhibition of mitochondrial fission through the use of Mdivi-1 (an inhibitor of DRP1). Mdivi-1 also partially prevented the release of cytochrome c from mitochondria to cytosol and attenuated cell apoptosis. Finally, given the accumulation of LC3II and SQSTM1/p62 and the obstruction of Parkin recruitment into damaged mitochondria in TM3 cells, the autophagosome-lysosome fusion was probably inhibited by cadmium. Overall, these findings suggest that cadmium induces apoptosis of mouse Leydig cells via the induction of excessive mitochondrial fission and inhibition of mitophagy.

Importance: Exposure to particulate matter (PM) has been associated with childhood asthma and wheeze. However, the specific associations between asthma and PM with an aerodynamic equivalent diameter of 1 μm or less (ie, PM₁), which is a contributor to PM_2.5 and potentially more toxic than PM_2.5, remain unclear.Objective: To investigate the association of early-life (prenatal and first year) exposure to size-segregated PM, including PM₁, PM_1-2.5, PM_2.5, PM_2.5-10, and PM₁₀, with childhood asthma and wheeze.Design, Setting, and Participants: This cross-sectional study was based on a questionnaire administered between June 2019 and June 2020 to caregivers of children aged 3 to 6 years in 7 Chinese cities (Wuhan, Changsha, Taiyuan, Nanjing, Shanghai, Chongqing, and Urumqi) as the second phase of the China, Children, Homes, Health study.Exposures: Exposure to PM₁, PM_1-2.5, PM_2.5, PM_2.5-10, and PM₁₀ during the prenatal period and first year of life.Main Outcomes and Measures: The main outcomes were caregiver-reported childhood asthma and wheeze. A machine learning–based space-time model was applied to estimate early-life PM₁, PM_2.5, and PM₁₀ exposure at 1 × 1-km resolution. Concentrations of PM_1-2.5 and PM_2.5-10 were calculated by subtracting PM₁ from PM_2.5 and PM_2.5 from PM₁₀, respectively. Multilevel (city and child) logistic regression models were applied to assess associations.Results: Of 29 418 children whose caregivers completed the survey (15 320 boys [52.1%]; mean [SD] age, 4.9 [0.9] years), 2524 (8.6%) ever had wheeze and 1161 (3.9%) were diagnosed with asthma. Among all children, 18 514 (62.9%) were breastfed for more than 6 months and 787 (2.7%) had parental history of atopy. A total of 22 250 children (75.6%) had a mother with an educational level of university or above. Of the 25 422 children for whom information about cigarette smoking exposure was collected, 576 (2.3%) had a mother who was a current or former smoker during pregnancy and 7525 (29.7%) had passive household cigarette smoke exposure in early life. Early-life PM₁, PM_2.5, and PM₁₀ exposure were significantly associated with increased risk of childhood asthma, with higher estimates per 10-μg/m³ increase in PM₁ (OR, 1.55; 95% CI, 1.27-1.89) than in PM_2.5 (OR, 1.14; 95% CI, 1.03-1.26) and PM₁₀ (OR, 1.11; 95% CI, 1.02-1.20). No association was observed between asthma and PM_1-2.5 exposure, suggesting that PM₁ rather than PM_1-2.5 contributed to the association between PM_2.5 and childhood asthma. There were significant associations between childhood wheeze and early-life PM₁ exposure (OR, 1.23; 95% CI, 1.07-1.41) and PM_2.5 exposure (OR, 1.08; 95% CI, 1.01-1.16) per 10-μg/m³ increase in PM₁ and PM_2.5, respectively.Conclusions and Relevance: In this cross-sectional study, higher estimates were observed for the association between PM with smaller particles, such as PM₁, vs PM with larger particles and childhood asthma. The results suggest that the association between PM_2.5 and childhood asthma was mainly attributable to PM₁.

Emerging evidence suggests that early-life (in-utero and first-year since birth) exposure to ambient PM_2.5 is a risk factor for asthma onset and exacerbation among children, while the hazards caused by PM_2.5 compositions remain largely unknown. To examine potential associations of early-life exposures to PM_2.5 mass and its major chemical constituents with childhood asthma and wheezing. By conducting the Phase II of the China, Children, Homes, Health study, we investigated 30,325 preschool children aged 3-6 years during 2019-2020 in mainland China. Early-life exposure to PM_2.5 mass and its constituents (i.e., black carbon [BC], organic matter [OM], nitrate, ammonium, sulfate) were calculated based on monthly estimates at a 1 km × 1 km resolution from satellite-based models. We adopted a novel quantile-based g-computation approach to assess the effect of a mixture of PM_2.5 constituents on childhood asthma/wheezing. The average PM_2.5 concentrations during in-utero and the first year since birth were 64.7 ± 10.6 and 61.8 ± 10.5 µg/m³, respectively. Early-life exposures to a mixture of major PM_2.5 constituents were significantly associated with increased risks of asthma and wheezing, while no evident compositions-wheezing associations were found in the first year. Each quintile increases in all five PM_2.5 components exposures in utero was accordingly associated with an odds ratio of 1.18 [95% confidence interval: 1.07-1.29] for asthma and 1.08 [1.01-1.16] for wheezing. BC, OM and SO₄^2- contributed more to risks of asthma and wheezing than the other PM_2.5 constituents during early life, wherein the effects of BC were only observed during pregnancy. Sex subgroup analyses suggested stronger associations among girls of first-year exposures to PM_2.5 components with childhood asthma. Early-life exposures to ambient PM_2.5, particularly compositions of BC, OM and SO₄^2-, are associated with an increased risk of childhood asthma.

Mammalian SPAG6, the orthologue of Chlamydomonas reinhardtii PF16, is a component of the central apparatus of the ‘9 + 2’ axoneme that controls ciliary/flagellar motility, including sperm motility. Recent studies revealed that SPAG6 has functions beyond its role in the central apparatus. Hence, we reexamined the role of SPAG6 in male fertility. In wild-type mice, SPAG6 was present in cytoplasmic vesicles in spermatocytes, the acrosome of round and elongating spermatids and the manchette of elongating spermatids. Spag6-deficient testes showed abnormal spermatogenesis, with abnormalities in male germ cell morphology consistent with the multi-compartment pattern of SPAG6 localization. The armadillo repeat domain of mouse SPAG6 was used as a bait in a yeast two-hybrid screen, and several proteins with diverse functions appeared multiple times, including Snapin, SPINK2 and COPS5. Snapin has a similar localization to SPAG6 in male germ cells, and SPINK2, a key protein in acrosome biogenesis, was dramatically reduced in Spag6-deficient mice which have defective acrosomes. SPAG16L, another SPAG6-binding partner, lost its localization to the manchette in Spag6-deficient mice. Our findings demonstrate that SPAG6 is a multi-functional protein that not only regulates sperm motility, but also plays roles in spermatogenesis in multiple cellular compartments involving multiple protein partners. Abstract Mammalian SPAG6, the orthologue of Chlamydomonas reinhardtii PF16, is a component of the central apparatus of the ‘9 + 2’ axoneme that controls ciliary/flagellar motility, including sperm motility. Recent studies revealed that SPAG6 has functions beyond its role in the central apparatus. Hence, we reexamined the role of SPAG6 in male fertility. In wild-type mice, SPAG6 was present in cytoplasmic vesicles in spermatocytes, the acrosome of round and elongating spermatids and the manchette of elongating spermatids. Spag6-deficient testes showed abnormal spermatogenesis, with abnormalities in male germ cell morphology consistent with the multi-compartment pattern of SPAG6 localization. The armadillo repeat domain of mouse SPAG6 was used as a bait in a yeast two-hybrid screen, and several proteins with diverse functions appeared multiple times, including Snapin, SPINK2 and COPS5. Snapin has a similar localization to SPAG6 in male germ cells, and SPINK2, a key protein in acrosome biogenesis, was dramatically reduced in Spag6-deficient mice which have defective acrosomes. SPAG16L, another SPAG6-binding partner, lost its localization to the manchette in Spag6-deficient mice. Our findings demonstrate that SPAG6 is a multi-functional protein that not only regulates sperm motility, but also plays roles in spermatogenesis in multiple cellular compartments involving multiple protein partners.