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Spermatid head retention as a marker of 2,5-hexanedione-induced testicular toxicity in the rat.

ABSTRACT: Histopathological analysis is a basic methodology for assessing testicular injury after exposure to candidate therapeutics or toxicants. One possible injury response in rat testis is the failure of step 19 spermatids to spermiate. Such spermatids are transported toward the basement membrane, where they are retained for degradation by Sertoli cells. In control rats, these retained spermatid heads (RSH) were observed at Stages IX-XII. Exposure to the Sertoli cell toxicant, 2,5-hexanedione (HD), for eighteen days at 0.08%-1.0% in drinking water resulted in a dose-dependent increase in the number of RSH at Stages IX-XII (no observed effect level [NOEL], 0.14%). To explore the dynamics of spermatid head retention, rats were treated with 0.33% or 1% HD for various durations and RSH were assessed across all stages. After 0.33% HD exposure for eighteen days, there were more RSH present in Stage IX-XII tubules compared to control. Numbers of RSH dropped back to control levels after four weeks of recovery after the eighteen-day exposure. Exposure of rats to 1% HD for eighteen days resulted in markedly elevated numbers of RSH at Stages IX-II/III. There was no evidence of other histopathological alterations. These data identify RSH as a sensitive histopathological marker of testicular toxicity for subacute HD exposure.

SUBMITTER: Bryant BH

PROVIDER: S-EPMC2574707 | biostudies-literature | 2008 Jun

REPOSITORIES: biostudies-literature

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Spermatid head retention as a marker of 2,5-hexanedione-induced testicular toxicity in the rat.

Bryant Bronwyn H BH Yamasaki Hideki H Sandrof Moses A MA Boekelheide Kim K

Toxicologic pathology 20080508 4

Histopathological analysis is a basic methodology for assessing testicular injury after exposure to candidate therapeutics or toxicants. One possible injury response in rat testis is the failure of step 19 spermatids to spermiate. Such spermatids are transported toward the basement membrane, where they are retained for degradation by Sertoli cells. In control rats, these retained spermatid heads (RSH) were observed at Stages IX-XII. Exposure to the Sertoli cell toxicant, 2,5-hexanedione (HD), fo ...[more]

PMID: 18467684

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Project description:Leber's hereditary optic neuropathy (LHON) is a maternally inherited blinding disease due to mitochondrial DNA (mtDNA) point mutations in complex I subunit genes, whose incomplete penetrance has been attributed to both genetic and environmental factors. Indeed, the mtDNA background defined as haplogroup J is known to increase the penetrance of the 11778/ND4 and 14484/ND6 mutations. Recently it was also documented that the professional exposure to n-hexane might act as an exogenous trigger for LHON. Therefore, we here investigate the effect of the n-hexane neurotoxic metabolite 2,5-hexanedione (2,5-HD) on cell viability and mitochondrial function of different cell models (cybrids and fibroblasts) carrying the LHON mutations on different mtDNA haplogroups. The viability of control and LHON cybrids and fibroblasts, whose mtDNAs were completely sequenced, was assessed using the MTT assay. Mitochondrial ATP synthesis rate driven by complex I substrates was determined with the luciferine/luciferase method. Incubation with 2,5-HD caused the maximal loss of viability in control and LHON cells. The toxic effect of this compound was similar in control cells irrespective of the mtDNA background. On the contrary, sensitivity to 2,5-HD induced cell death was greatly increased in LHON cells carrying the 11778/ND4 or the 14484/ND6 mutation on haplogroup J, whereas the 11778/ND4 mutation in association with haplogroups U and H significantly improved cell survival. The 11778/ND4 mutation on haplogroup U was also more resistant to inhibition of complex I dependent ATP synthesis by 2,5-HD. In conclusion, this study shows that mtDNA haplogroups modulate the response of LHON cells to 2,5-HD. In particular, haplogroup J makes cells more sensitive to its toxic effect. This is the first evidence that an mtDNA background plays a role by interacting with an environmental factor and that 2,5-HD may be a risk element for visual loss in LHON. This proof of principle has broad implications for other neurodegenerative disorders such as Parkinson's disease.

Project description:BackgroundN-hexane, with its metabolite 2,5-hexanedine (HD), is an industrial hazardous material. Chronic hexane exposure causes segmental demyelination in the peripheral nerves, and high-dose intoxication may also affect central nervous system. Demyelinating conditions are difficult to treat and stem cell therapy using bone marrow mesenchymal stem cells (BMSCs) is a promising novel strategy. Our previous study found that BMSCs promoted motor function recovery in rats modeling hexane neurotoxicity. This work aimed to explore the underlying mechanisms and focused on the changes in spinal cord.MethodsSprague Dawley rats were intoxicated with HD (400 mg/kg/day, i.p, for 5 weeks). A bolus of BMSCs (5 × 107 cells/kg) was injected via tail vein. Demyelination and remyelination of the spinal cord before and after BMSC treatment were examined microscopically. Cultured oligodendrocyte progenitor cells (OPCs) were incubated with HD ± BMSC-derived conditional medium (BMSC-CM). OPC differentiation was studied by immunostaining and morphometric analysis. The expressional changes of Hes1, a transcription factor negatively regulating OPC-differentiation, were studied. The upstream Notch1 and TNFα/RelB pathways were studied, and some key signaling molecules were measured. The correlation between neurotrophin NGF and TNFα was also investigated. Statistical significance was evaluated using one-way ANOVA and performed using SPSS 13.0.ResultsThe demyelinating damage by HD and remyelination by BMSCs were evidenced by electron microscopy, LFB staining and NG2/MBP immunohistochemistry. In vitro cultured OPCs showed more differentiation after incubation with BMSC-CM. Hes1 expression was found to be significantly increased by HD and decreased by BMSC or BMSC-CM. The change of Hes1 was found, however, independent of Notch1 activation, but dependent on TNFα/RelB signaling. HD was found to increase TNFα, RelB and Hes1 expression, and BMSCs were found to have the opposite effect. Addition of recombinant TNFα to OPCs or RelB overexpression similarly caused upregulation of Hes1 expression. The secretion of NGF by BMSC and activation of NGF receptor was found important for suppression of TNFα production in OPCs.ConclusionsOur findings demonstrated that BMSCs promote remyelination in the spinal cord of HD-exposed rats via TNFα/RelB-Hes1 pathway, providing novel insights for evaluating and further exploring the therapeutical effect of BMSCs on demyelinating neurodegenerative disease.

Dataset Information

Spermatid head retention as a marker of 2,5-hexanedione-induced testicular toxicity in the rat.

Publications

Spermatid head retention as a marker of 2,5-hexanedione-induced testicular toxicity in the rat.

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