Activation Of Cytoprotective Genes Research Articles

Polyunsaturated fatty acids and p38-MAPK link metabolic reprogramming to cytoprotective gene expression during dietary restriction

The metabolic state of an organism instructs gene expression modalities, leading to changes in complex life history traits, such as longevity. Dietary restriction (DR), which positively affects health and life span across species, leads to metabolic reprogramming that enhances utilisation of fatty acids for energy generation. One direct consequence of this metabolic shift is the upregulation of cytoprotective (CyTP) genes categorized in the Gene Ontology (GO) term of “Xenobiotic Detoxification Program” (XDP). How an organism senses metabolic changes during nutritional stress to alter gene expression programs is less known. Here, using a genetic model of DR, we show that the levels of polyunsaturated fatty acids (PUFAs), especially linoleic acid (LA) and eicosapentaenoic acid (EPA), are increased following DR and these PUFAs are able to activate the CyTP genes. This activation of CyTP genes is mediated by the conserved p38 mitogen-activated protein kinase (p38-MAPK) pathway. Consequently, genes of the PUFA biosynthesis and p38-MAPK pathway are required for multiple paradigms of DR-mediated longevity, suggesting conservation of mechanism. Thus, our study shows that PUFAs and p38-MAPK pathway function downstream of DR to help communicate the metabolic state of an organism to regulate expression of CyTP genes, ensuring extended life span.

Carbon monoxide releasing molecule-A1 improves nonalcoholic steatohepatitis via Nrf2 activation mediated improvement in oxidative stress and mitochondrial function

Nuclear factor-erythroid 2 related factor 2 (Nrf2)-mediated signaling plays a central role in maintaining cellular redox homeostasis of hepatic cells. Carbon monoxide releasing molecule-A1 (CORM-A1) has been reported to stimulate up-regulation and nuclear translocation of Nrf2 in hepatocytes. However, the role of CORM-A1 in improving lipid metabolism, antioxidant signaling and mitochondrial functions in nonalcoholic steatohepatitis (NASH) is unknown. In this study, we report that CORM-A1 prevents hepatic steatosis in high fat high fructose (HFHF) diet fed C57BL/6J mice, used as model of NASH. The beneficial effects of CORM-A1 in HFHF fed mice was associated with improved lipid homeostasis, Nrf2 activation, upregulation of antioxidant responsive (ARE) genes and increased ATP production. As, mitochondria are intracellular source of reactive oxygen species (ROS) and important sites of lipid metabolism, we further investigated the mechanisms of action of CORM-A1-mediated improvement in mitochondrial function in palmitic acid (PA) treated HepG2 cells. Cellular oxidative stress and cell viability were found to be improved in PA + CORM-A1 treated cells via Nrf2 translocation and activation of cytoprotective genes. Furthermore, in PA treated cells, CORM-A1 improved mitochondrial oxidative stress, membrane potential and rescued mitochondrial biogenesis thru upregulation of Drp1, TFAM, PGC-1α and NRF-1 genes. CORM-A1 treatment improved cellular status by lowering glycolytic respiration and maximizing OCR. Improvement in mitochondrial respiration and increment in ATP production in PA + CORM-A1 treated cells further corroborate our findings. In summary, our data demonstrate for the first time that CORM-A1 ameliorates tissue damage in steatotic liver via Nrf2 activation and improved mitochondrial function, thus, suggesting the anti-NASH potential of CORM-A1.

The extracellular matrix signals through protein kinase MEKK‐3 and transcription factor ATF‐7 to activate cytoprotective genes

Animal cells secrete proteins and carbohydrates to create an extracellular matrix (ECM) that provides mechanical support for tissues. Rather than being an inert scaffold, the ECM is a dynamic, physiologically active component in living tissues. Barrier ECMs stand at the surface of animals and are the first of line defense against many environmental stressors such as osmotic pressure changes, toxins, and biological pathogens. Activation of cytoprotective genes is the second line of defense against environmental stress. Cytoprotective genes are conserved and influence adaptation to climate change, disease progression and pathogenesis, and aging. Therefore, a molecular understanding of fundamental signaling mechanisms that control cytoprotective genes has broad relevance. The molecular signaling pathways that sense and regulate cytoprotective responses within cells have been studied in detail, but far less is known about how barrier ECMs interact with environmental stress to influence cytoprotective gene regulation. The nematode model organism Caenorhabditis elegans is covered by a complex barrier ECM termed the cuticle. Given that the cuticle directly interacts with the environment, we hypothesize that it may include a sensor for stress. We recently used RNAi screening, collagen mutations, and RNAseq in C. elegans to demonstrate that disruption of specific bands of collagen, called annular furrows, significantly induce organic osmolyte, detoxification, and immunity cytoprotective genes (p<0.05) (Dodd et al., 2018 Genetics 208:1467). To identify regulators of cytoprotective gene transcription downstream of annular furrows, we conduced an RNAi screen of all C. elegans' protein kinases and transcription factors in annular furrow mutants expressing fluorescent cytoprotective gene reporters. This screen and subsequent RT‐qPCR analysis identified protein kinase MEKK‐3 and transcription factor ATF‐7 as significantly required for expression of cytoprotective genes* in annular furrow mutants (p>0.001; *atf‐7 knockdown did not significantly repress immunity gene induction). Previous C. elegans' literature indicates that MEKK‐3 regulates longevity with dietary restriction and that ATF‐7 regulates innate immunity. Importantly, both of these proteins are conserved in humans where they regulate diverse stress responses and are implicated in tumorigenesis. We are now leveraging the experimental tractability of C. elegans to determine how these two conserved signaling genes function to confer protection to environmental stress in this novel ECM‐initiated context.Support or Funding InformationNSF, UF Graduate School Fellowship, McKnight Doctoral Fellowship, William Townsend Porter Predoctoral Fellowship from the American Physiological SocietyThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Characterization of Nrf1b, a Novel Isoform of the Nuclear Factor-Erythroid-2 Related Transcription Factor-1 That Activates Antioxidant Response Element-Regulated Genes

Nuclear factor E2-related factor 1 (Nrf1) is a basic leucine zipper transcription factor that plays an important role in the activation of cytoprotective genes through the antioxidant response elements. The previously characterized long isoform of Nrf1 (Nrf1a) is targeted to the endoplasmic reticulum and accumulates in the nucleus in response to activating signals. Here we characterized a novel Nrf1 protein isoform (Nrf1b) generated through an alternative promoter and first exon that lacks the ER targeting domain of Nrf1a. The 5′-flanking region of Nrf1b directed high levels of luciferase reporter expression in cells. RT-PCR and Western blotting showed Nrf1b is widely expressed in various cell lines and mouse tissues. Immunoblot analysis of subcellular fractions and imaging of green fluorescence protein (GFP)-tagged Nrf1b demonstrate Nrf1b is constitutively localized to the nucleus. Nrf1b can activate GAL4-dependent transcription when fused to the heterologous GAL4 DNA-binding domain. Gel-shift and coimmunoprecipitation experiments demonstrate that Nrf1b forms a complex with MafG, and expression of Nrf1b activates the expression of antioxidant response element containing reporters and genes in cells. These results suggest Nrf1b is targeted to the nucleus where it activates ARE-driven genes and may play a role in modulating antioxidant response elements.

Resistance to Cancer Treatment: The Role of Somatic Genetic Events and the Challenges for Targeted Therapies

Therapeutic resistance remains a major cause of cancer-related deaths. Resistance can occur from the outset of treatment or as an acquired phenomenon after an initial clinical response. Therapeutic resistance is an almost universal phenomenon in the treatment of metastatic cancers. The advent of molecularly targeted treatments brought greater efficacy in patients whose tumors express a particular target or molecular signature. However, resistance remains a predictable challenge. This article provides an overview of somatic genomic events that confer resistance to cancer therapies. Some examples, including BCR–Abl, EML4–ALK, and the androgen receptor, contain mutations in the target itself, which hamper binding and inhibitory functions of therapeutic agents. There are also examples of somatic genetic changes in other genes or pathways that result in resistance by circumventing the inhibitor, as in resistance to trastuzumab and BRAF inhibitors. Yet other examples results in activation of cytoprotective genes. The fact that all of these mechanisms of resistance are due to somatic changes in the tumor’s genome makes targeting them selectively a feasible goal. To identify and validate these changes, it is important to obtain biopsies of clinically resistant tumors. A rational consequence of this evolving knowledge is the growing appreciation that combinations of inhibitors will be needed to anticipate and overcome therapeutic resistance.

Nrf2 establishes a glutathione-mediated gradient of UVB cytoprotection in the epidermis

Ultraviolet (UV) B irradiation can severely damage the skin and even induce tumorigenesis. It exerts its effects by direct DNA modification and by formation of reactive oxygen species (ROS). We developed a strategy to genetically activate target gene expression of the transcription factor NF-E2-related factor 2 (Nrf2) in keratinocytes in vivo based on expression of a constitutively active Nrf2 mutant. Activation of Nrf2 target genes strongly reduced UVB cytotoxicity through enhancement of ROS detoxification. Remarkably, the protective effect was extended to neighboring cells. Using different combinations of genetically modified mice, we demonstrate that Nrf2 activates the production, recycling, and release of glutathione and cysteine by suprabasal keratinocytes, resulting in protection of basal cells in a paracrine, glutathione/cysteine-dependent manner. Most importantly, we found that endogenous Nrf2 controls selective protection of suprabasal keratinocytes from UVB-induced apoptosis through activation of cytoprotective genes. This finding explains the preferential UVB-induced apoptosis of basal cells, which is important for elimination of mutated stem cells as well as for preservation of skin integrity. Taken together, our results identify Nrf2 as a key regulator in the UV response of the skin.

Cyclopentenone Prostaglandins as Anti-Inflammatory Agents: A Novel Therapeutic Strategy?

Cyclopentenone prostaglandins (cyPG) are naturally occurring derivatives of prostaglandin E1, E2, and D2 containing an α,β-unsaturated carbonyl group in the cyclopentane ring structure (cyclopentenone). These molecules exhibit a wide array of biological activities, including anti-inflammatory effects, by interacting with intracellular target proteins. A large body of evidence shows that cyPG mainly interact with signal proteins and transcription factors, such as “Nuclear Factor-kB” (NF-κB), “Heat Shock Factor-1” (HSF1), and Peroxisome Proliferator Activated Receptor-γ (PPAR- γ), which play crucial and opposite roles in inflammatory diseases. NF-κB is an early mediator of immune and inflammatory responses whereas HSF1, and PPAR-γ activation have been related to mechanisms leading to the resolution of inflammation. The identification of cyclopentenone as the active moiety of cyPG responsible for HSF1 activation as well as for the inhibition of inflammatory genes in human cells, opens new perspectives for the design and development of a new class of cytoprotective molecules devoid of the pleiotropic effects of natural eicosanoids. In this review we summarize the recent information on the anti-inflammatory effect of cyclopentenones and discuss the possible development of novel therapeutic strategies relying upon the simultaneous activation of cytoprotective genes and down-regulation of inflammatory genes.