Progressive Rotavirus Infection Downregulates Redox-Sensitive Transcription Factor Nrf2 and Nrf2-Driven Transcription Units

Abstract

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.

Induction of Reactive Oxygen Species Is Necessary for Efficient Onset of Cyprinid Herpesvirus 2 Replication: Implications for Novel Antiviral Strategy With Antioxidants

“…The Nrf2-dependent antioxidative pathway is regarded as an adaptive cellular response to oxidative and electrophilic stress and a responsive host defense system if caused by a viral infection. In a study to apply Nrf2 agonists as anti-rotaviral drugs, initial induction of Nrf2 concurred with a virus-induced early burst of oxidative stress, and rotavirus infection was determined to be sensitive to antioxidant treatments (Patra et al, 2020). NrF2 belongs to the CNC family and is mainly involved in the elimination of cell endogenous ROS.…”

NRF2 in Viral Infection

“…By contrast, the expression of KEAP1 was increased at both mRNA and protein level, suggesting that EV71 targets NRF2 through induction of its inhibitor [ 38 ]. Another recent example of the mechanisms of NRF2 downregulation is given by Patra et al [ 39 ] who showed in African green monkey fetal kidney cell line infected with simian rotavirus RV-SA11 that rotavirus infection also downregulated NRF2. Interestingly, NRF2 downregulation occurs after an initial upregulation of NRF2 triggered by the oxidative stress generated by the viral replication.…”

“…Moreover, after 3 h post infection, the authors observed by western blotting that NRF2 protein level and target genes such as HO-1, NQO1, and SOD1 were downregulated. Moreover, using the proteasome inhibitor MG132, Patra et al demonstrated the importance of the proteasome in NRF2 downregulation during RV infection, suggesting that RV infection downregulates NRF2 through the proteasomal degradation [ 39 ]. Another virus suppressing NRF2 activity is HCV, as demonstrated in human hepatocytic cell lines by Monica Carvajal-Yepes and her colleagues [ 40 ].…”

Treading a HOSTile path: Mapping the dynamic landscape of host cell–rotavirus interactions to explore novel host-directed curative dimensions

“…Initial induction of Nrf2 concurred with RV-induced early burst of oxidative stress and therefore was sensitive to treatments with anti-oxidants. Reduction of Nrf2 levels beyond initial hours, however, was found to be independent of cellular redox status and canonical Nrf2 turn-over pathway but dependent on ubiquitin-proteasome system through a non-canonical E3 ubiquitin ligase ( Figure 3d ) [ 171 ].…”