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Knockout of the transcription factor NRF2 disrupts spermatogenesis in an age-dependent manner.

ABSTRACT: Oxidative stress occurs when generation of reactive oxygen species (ROS) overwhelms antioxidant defenses. Oxidative stress has been associated with male infertility. The transcription factor nuclear factor-erythroid 2-related factor 2 (NRF2) regulates basal and inducible transcription of genes encoding enzymes important for protection against ROS. We hypothesized that deletion of the Nrf2 gene causes testicular and epididymal oxidative stress, which disrupts spermatogenesis. Our results show that male Nrf2(-/-) mice have decreased fertility compared to wild-type and heterozygous littermates, due to accumulating seminiferous tubule damage with increasing age. Testicular sperm head counts, epididymal sperm counts, and epididymal sperm motility in 2-month-old Nrf2(-/-) males did not differ from those of wild-type littermates; however, by age 6 months, Nrf2(-/-) males had 44% lower testicular sperm head counts, 65% lower epididymal sperm counts, and 66% lower epididymal sperm motility than wild-type males. Two- to 4-month-old Nrf2(-/-) males had elevated levels of testicular and epididymal lipid peroxidation and testicular germ cell apoptosis, and decreased levels of antioxidants, compared to wild-type males. These results provide evidence that oxidative stress has deleterious effects on the testis and epididymis and demonstrate a critical role for the transcription factor NRF2 in preventing oxidative disruption of spermatogenesis.

SUBMITTER: Nakamura BN

PROVIDER: S-EPMC2948056 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

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Knockout of the transcription factor NRF2 disrupts spermatogenesis in an age-dependent manner.

Nakamura Brooke N BN Lawson Gregory G Chan Jefferson Y JY Banuelos Jésus J Cortés Mabel M MM Hoang Yvonne D YD Ortiz Laura L Rau Bogdan A BA Luderer Ulrike U

Free radical biology & medicine 20100805 9

Oxidative stress occurs when generation of reactive oxygen species (ROS) overwhelms antioxidant defenses. Oxidative stress has been associated with male infertility. The transcription factor nuclear factor-erythroid 2-related factor 2 (NRF2) regulates basal and inducible transcription of genes encoding enzymes important for protection against ROS. We hypothesized that deletion of the Nrf2 gene causes testicular and epididymal oxidative stress, which disrupts spermatogenesis. Our results show tha ...[more]

PMID: 20692336

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Project description:Eukaryotic cells adopt highly tuned stress response physiology under threats of exogenous stressors including viruses to maintain cellular homeostasis. Not surprisingly, avoidance of cellular stress response pathways is an essential facet of virus-induced obligatory host reprogramming to invoke a cellular environment conducive to viral perpetuation. Adaptive cellular responses to oxidative and electrophilic stress are usually taken care of by an antioxidant defense system, core to which lies the redox-responsive transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) and Nrf2-driven transcriptional cascade. Deregulation of host redox balance and redox stress-sensitive Nrf2 antioxidant defense have been reported for many viruses. In the current study, we aimed to study the modulation of the Nrf2-based host cellular redox defense system in response to Rotavirus (RV) infection in vitro. Interestingly, we found that Nrf2 protein levels decline sharply with progression of RV infection beyond an initial upsurge. Moreover, Nrf2 decrease as a whole was found to be accompanied by active nuclear vacuity of Nrf2, resulting in lowered expression of stress-responsive Nrf2 target genes heme oxygenase-1 (HO-1), NAD(P)H quinone dehydrogenase 1, and superoxide dismutase 1 both in the presence and absence of Nrf2-driven transcriptional inducers. Initial induction of Nrf2 concurred with RV-induced early burst of oxidative stress and therefore was sensitive to treatments with antioxidants. Reduction of Nrf2 levels beyond initial hours, however, was found to be independent of the cellular redox status. Furthermore, increasing the half-life of Nrf2 through inhibition of the Kelch-like erythroid cell-derived protein with CNC homology- (ECH-) associated protein 1/Cullin3-RING Box1-based canonical Nrf2 turnover pathway could not restore Nrf2 levels post RV-SA11 infection. Depletion of the Nrf2/HO-1 axis was subsequently found to be sensitive to proteasome inhibition with concurrent observation of increased K48-linked ubiquitination associated with Nrf2. Together, the present study describes robust downregulation of Nrf2-dependent cellular redox defense beyond initial hours of RV infection, justifying our previous observation of potent antirotaviral implications of Nrf2 agonists.

Project description:BackgroundTranscription factor knockout microarrays (TFKMs) provide useful information about gene regulation. By using statistical methods for detecting differentially expressed genes between the gene expression microarray data of the mutant and wild type strains, the TF knockout targets of the knocked-out TF can be identified. However, the identified TF knockout targets may contain a certain amount of false positives due to the experimental noises inherent in the high-throughput microarray technology. Even if the identified TF knockout targets are true, the molecular mechanisms of how a TF regulates its TF knockout targets remain unknown by this kind of statistical approaches.ResultsTo solve these two problems, we developed a method to filter out the false positives in the original TF knockout targets (identified by statistical approaches) so that the biologically interpretable TF knockout targets can be extracted. Our method can further generate experimentally testable hypotheses of the molecular mechanisms of how a TF regulates its biologically interpretable TF knockout targets. The details of our method are as follows. First, a TF binding network was constructed using the ChIP-chip data deposited in the YEASTRACT database. Then for each original TF knockout target, it is said to be biologically interpretable if a path (in the TF binding network) from the knocked-out TF to this target could be identified by our path search algorithm. The identified path explains how the TF may regulate this target either directly by binding to its promoter or indirectly through intermediate TFs. After checking all the original TF knockout targets, the biologically interpretable ones could be extracted and the false positives could be filtered out. We validated the biological significance of our refined (i.e., biologically interpretable) TF knockout targets by assessing their functional enrichment, expression coherence, and the prevalence of protein-protein interactions. Our refined TF knockout targets outperform the original TF knockout targets across all measures.ConclusionsBy jointly analyzing the TFKM and ChIP-chip data, our method can extract the biologically interpretable TF knockout targets by identifying paths (in the TF binding network) from the knocked-out TF to these targets. The identified paths form experimentally testable hypotheses regarding the molecular mechanisms of how a TF may regulate its knockout targets. About seven hundred hypotheses generated by our methods have been experimentally validated in the literature. Our work demonstrates that integrating different data sources is a powerful approach to study complex biological systems.

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Knockout of the transcription factor NRF2 disrupts spermatogenesis in an age-dependent manner.

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Knockout of the transcription factor NRF2 disrupts spermatogenesis in an age-dependent manner.

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