Abstract Interstitial lung diseases such as idiopathic pulmonary fibrosis (IPF) are caused by persistent micro-injuries to alveolar epithelial tissues accompanied by aberrant repair processes. IPF is currently treated with pirfenidone and nintedanib, compounds which slow the rate of disease progression but fail to target underlying pathophysiological mechanisms. The DNA repair protein 8-oxoguanine DNA glycosylase-1 (OGG1) has significant roles in the modulation of inflammation and metabolic syndromes. Currently, no pharmaceutical solutions targeting OGG1 have been utilized in the treatment of IPF. In this study we show Ogg1 -targeting siRNA mitigates bleomycin-induced pulmonary fibrosis in male mice, highlighting OGG1 as a tractable target in lung fibrosis. The small molecule OGG1 inhibitor, TH5487, decreases myofibroblast transition and associated pro-fibrotic gene expressions in fibroblast cells. In addition, TH5487 decreases levels of pro-inflammatory mediators, inflammatory cell infiltration, and lung remodeling in a murine model of bleomycin-induced pulmonary fibrosis conducted in male C57BL6/J mice. OGG1 and SMAD7 interact to induce fibroblast proliferation and differentiation and display roles in fibrotic murine and IPF patient lung tissue. Taken together, these data suggest that TH5487 is a potentially clinically relevant treatment for IPF but further study in human trials is required.
Oxidative modification(s) to nucleic acid bases are an unavoidable consequence of reactions by reactive oxygen species. Arguably, the most abundant ROS-generated lesion in nuclear and mitochondrial DNA is 7, 8-dihydro-8-oxoguanine (8-oxoGua), which is repaired primarily by 8-oxoguanine DNA glycosylase 1, in the OGG1-initiated base excision repair pathway. Deficiency in OGG1 repair is believed to have role(s) in development and progression of various disease processes, including neurodegenerative, cardiovascular, metabolic diseases, and aging-associated pathologies. The common link among these diseases is acute/chronic inflammatory processes. Emerging data support the idea that OGG1-induced adjustments in DNA structure at genomic 8-oxoGua with or without excision, serve as a nucleation site for transcription factor binding allowing prompt expression of genes, essential for reestablishment of a homeostatic state via innate and adaptive immune responses after exposure to biological and/or cytotoxic agents. As part of the immune defenses, OGG1 in complex with a free 8-oxoGua base also exerts transcriptional control via small GTPase signaling pathways. These data are consistent with the limited immune responses of Ogg1 knockout mice. Thus, evolution integrated genome maintenance by OGG1-BER and control host homeostatic state via inflammation, which, if not controlled, can be one of the mechanistic explanations for OGG1's previously proposed link to diseases and aging processes.
Abstract Respiratory syncytial virus (RSV) infection induces an oxidizing environment linked to increased viral load, expression of pro-inflammatory genes, and excessive lung inflammation. The mechanisms of how reactive oxygen species (ROS) promotes viral gene expression have remained largely elusive. Here we show that nascent (n)RNAs of RSV acquire 8-oxo-7,8-dihydroguanine (8-oxo(r)Gua) -a covalently modified guanine base in their 5’-UTR peritranscriptionally, while paired with the 3’-terminus of viral gene(s). 8-oxo(r)Gua is bound by 8-oxoguanine DNA glycosylase1 (OGG1), a complex that physically interacts with and recruits the anti-terminator protein M2-1 to increase viral gene transcription. Knockdown of OGG1 (but not other DNA glycosylases) or inhibition of its binding, significantly decreased RSV mRNA, protein levels and yield of progeny in cultured cells and airways. Collectively, these data suggest that Gua oxidation in vRNA, serves as an epitranscriptomic mark that repurposes OGG1 to increase lytic viral replication. Pharmacological inhibition of OGG1 binding to the epitranscriptomic mark could have clinical utility to decrease manifestations of RSV infection.
The bronchial vascular endothelial network plays important roles in pulmonary pathology during respiratory viral infections, including respiratory syncytial virus (RSV), influenza A(H1N1) and importantly SARS-Cov-2. All of these infections can be severe and even lethal in patients with underlying risk factors.A major obstacle in disease prevention is the lack of appropriate efficacious vaccine(s) due to continuous changes in the encoding capacity of the viral genome, exuberant responsiveness of the host immune system and lack of effective antiviral drugs. Current management of these severe respiratory viral infections is limited to supportive clinical care. The primary cause of morbidity and mortality is respiratory failure, partially due to endothelial pulmonary complications, including edema. The latter is induced by the loss of alveolar epithelium integrity and by pathological changes in the endothelial vascular network that regulates blood flow, blood fluidity, exchange of fluids, electrolytes, various macromolecules and responses to signals triggered by oxygenation, and controls trafficking of leukocyte immune cells. This overview outlines the latest understanding of the implications of pulmonary vascular endothelium involvement in respiratory distress syndrome secondary to viral infections. In addition, the roles of infection-induced cytokines, growth factors, and epigenetic reprogramming in endothelial permeability, as well as emerging treatment options to decrease disease burden, are discussed.
Abstract Compromised DNA repair capacity of individuals could play a critical role in the severity of SARS-CoV-2 infection-induced COVID-19. We therefore analyzed the expression of DNA repair genes in publicly available transcriptomic datasets of COVID-19 patients and found that the level of NEIL2, an oxidized base specific mammalian DNA glycosylase, is particularly low in the lungs of COVID-19 patients displaying severe symptoms. Downregulation of pulmonary NEIL2 in CoV-2-permissive animals and postmortem COVID-19 patients validated these results. To investigate the potential roles of NEIL2 in CoV-2 pathogenesis, we infected Neil2 -null ( Neil2 −/− ) mice with a mouse-adapted CoV-2 strain and found that Neil2 −/− mice suffered more severe viral infection concomitant with increased expression of proinflammatory genes, which resulted in an enhanced mortality rate of 80%, up from 20% for the age matched Neil2 +/+ cohorts. We also found that infected animals accumulated a significant amount of damage in their lung DNA. Surprisingly, recombinant NEIL2 delivered into permissive A549-ACE2 cells significantly decreased viral replication. Toward better understanding the mechanistic basis of how NEIL2 plays such a protective role against CoV-2 infection, we determined that NEIL2 specifically binds to the 5’-UTR of SARS-CoV-2 genomic RNA and blocks protein synthesis. Together, our data suggest that NEIL2 plays a previously unidentified role in regulating CoV-2-induced pathogenesis, via inhibiting viral replication and preventing exacerbated proinflammatory responses, and also via its well-established role of repairing host genome damage.
8‐Oxoguanine DNA glycosylase‐1 (OGG1)‐initiated base excision repair pathway is primarily responsible for 7, 8‐dihydro‐8‐oxoguanine (8‐oxoG) removal from DNA. Recent studies, however, have shown that 8‐oxoG in gene regulatory elements may serve as an epigenetic mark, and OGG1 has distinct functions in modulating gene expression. Genome‐wide mapping of oxidative stress‐induced OGG1 enrichment within introns was documented, but its significance has not yet been fully characterized. Here, we explored whether OGG1 recruited to intron 1 of tissue inhibitor of metalloproteinase‐1 (TIMP1) gene and modulated its expression. Using chromatin and DNA:RNA hybrid immunoprecipitation assays, we report recruitment of OGG1 to the DNA:RNA hybrid in intron 1, where it increases nascent RNA but lowers mRNA levels in O 3 ‐exposed human airway epithelial cells and mouse lungs. Decrease in TIMP1 expression is alleviated by antioxidant administration, small interfering RNA depletion, or inhibition of OGG1 binding to its genomic substrate. In vitro studies revealed direct interaction between OGG1 and 8‐oxoG containing DNA:RNA hybrid, without excision of its substrate. Inhibition of OGG1 binding to DNA:RNA hybrid translated into an increase in TIMP1 expression and a decrease in oxidant‐induced lung inflammatory responses as well as airway remodeling. Data documented here reveal a novel molecular link between OGG1 at damaged sites and transcription dynamics that may contribute to oxidative stress‐induced cellular and tissue responses.—Pan, L., Wang, H., Luo, J., Zeng J., Pi, J., Liu, H., Liu, C., Ba, X., Qu, X., Xiang Y., Boldogh, I., Qin, X. Epigenetic regulation of TIMP1 expression by 8‐oxoguanine DNA glycosylase‐1 binding to DNA:RNA hybrid. FASEB J. 33, 14159‐14170 (2019). www.fasebj.org
Bombesin receptor-activated protein (BRAP) and its homologous protein in mice, which is encoded by bc004004 gene, were expressed abundantly in brain tissues with unknown functions. We treated bc004004-/- mice with chronic unpredictable mild stress (CUMS) to test whether those mice were more vulnerable to stress-related disorders. The results of forced swimming test, sucrose preference test, and open field test showed that after being treated with CUMS for 28 days or 35 days both bc004004-/- and bc004004+/+ mice exhibited behavioural changes and there was no significant difference between bc004004+/+ and bc004004-/-. However, behavioural changes were observed only in bc004004-/- mice after being exposed to CUMS for 21 days, but not in bc004004+/+ after 21-day CUMS exposure, indicating that lack of BRAP homologous protein may cause vulnerability to stress-related disorders in mice. In addition, bc004004-/- mice showed a reduction in recognition memory as revealed by novel object recognition test. Since memory changes and stress related behavioural changes are all closely related to the hippocampus function we further analyzed the changes of dendrites and synapses of hippocampal neurons as well as expression levels of some proteins closely related to synaptic function. bc004004-/- mice exhibited decreased dendritic lengths and increased amount of immature spines, as well as altered expression pattern of synaptic related proteins including GluN2A, synaptophysin and BDNF in the hippocampus. Those findings suggest that BRAP homologous protein may have a protective effect on the behavioural response to stress via regulating dendritic spine formation and synaptic plasticity in the hippocampus.
Abstract DNA repair protein counteracting oxidative promoter lesions may modulate gene expression. Oxidative DNA bases modified by reactive oxygen species (ROS), primarily as 7, 8-dihydro-8-oxo-2′-deoxyguanosine (8-oxoG), which is repaired by 8-oxoguanine DNA glycosylase1 (OGG1) during base excision repair (BER) pathway. Because cellular response to oxidative challenge is accompanied by DNA damage repair, we tested whether the repair by OGG1 is compatible with transcription factor binding and gene expression. We performed electrophoretic mobility shift assay (EMSA) using wild-type sequence deriving from Cxcl2 gene promoter and the same sequence bearing a single synthetic 8-oxoG at defined 5′ or 3′ guanine in runs of guanines to mimic oxidative effects. We showed that DNA occupancy of NF-κB present in nuclear extracts from tumour necrosis factor alpha (TNFα) exposed cells is OGG1 and 8-oxoG position dependent, importantly, OGG1 counteracting 8-oxoG outside consensus motif had a profound influence on purified NF-κB binding to DNA. Furthermore, OGG1 is essential for NF-κB dependent gene expression, prior to 8-oxoG excised from DNA. These observations imply that pre-excision step(s) during OGG1 initiated BER evoked by ROS facilitates NF-κB DNA occupancy and gene expression.
Bombesin receptor-activated protein (BRAP) and its homologous protein in mice, which is encoded by bc004004 gene, were expressed abundantly in brain tissues with unknown functions. We treated bc004004-/- mice with chronic unpredictable mild stress (CUMS) to test whether those mice were more vulnerable to stress-related disorders. The results of forced swimming test, sucrose preference test, and open field test showed that after being treated with CUMS for 28 days or 35 days both bc004004-/- and bc004004+/+ mice exhibited behavioural changes and there was no significant difference between bc004004+/+ and bc004004-/-. However, behavioural changes were observed only in bc004004-/- mice after being exposed to CUMS for 21 days, but not in bc004004+/+ after 21-day CUMS exposure, indicating that lack of BRAP homologous protein may cause vulnerability to stress-related disorders in mice. In addition, bc004004-/- mice showed a reduction in recognition memory as revealed by novel object recognition test. Since memory changes and stress related behavioural changes are all closely related to the hippocampus function we further analyzed the changes of dendrites and synapses of hippocampal neurons as well as expression levels of some proteins closely related to synaptic function. bc004004-/- mice exhibited decreased dendritic lengths and increased amount of immature spines, as well as altered expression pattern of synaptic related proteins including GluN2A, synaptophysin and BDNF in the hippocampus. Those findings suggest that BRAP homologous protein may have a protective effect on the behavioural response to stress via regulating dendritic spine formation and synaptic plasticity in the hippocampus.
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