TXNRD1 drives the innate immune response in senescent cells with implications for age-associated inflammation

Sterile inflammation, also known as 'inflammaging', is a hallmark of tissue aging. Cellular senescence contributes to tissue aging, in part, through the secretion of proinflammatory factors collectively known as the senescence-associated secretory phenotype (SASP). The genetic variability of thioredoxin reductase 1 (TXNRD1) is associated with aging and age-associated phenotypes such as late-life survival, activity of daily living and physical performance in old age. TXNRD1's role in regulating tissue aging has been attributed to its enzymatic role in cellular redox regulation. Here, we show that TXNRD1 drives the SASP and inflammaging through the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) innate immune response pathway independently of its enzymatic activity. TXNRD1 localizes to cytoplasmic chromatin fragments and interacts with cGAS in a senescence-status-dependent manner, which is necessary for the SASP. TXNRD1 enhances the enzymatic activity of cGAS. TXNRD1 is required for both the tumor-promoting and immune surveillance functions of senescent cells, which are mediated by the SASP in vivo in mouse models. Treatment of aged mice with a TXNRD1 inhibitor that disrupts its interaction with cGAS, but not with an inhibitor of its enzymatic activity alone, downregulated markers of inflammaging in several tissues. In summary, our results show that TXNRD1 promotes the SASP through the innate immune response, with implications for inflammaging. This suggests that the TXNRD1-cGAS interaction is a relevant target for selectively suppressing inflammaging.

Imaging-based chromatin and epigenetic age, ImAge, quantitates aging and rejuvenation

Biomarkers of biological age that predict the risk of disease and expected lifespan better than chronological age are key to efficient and cost-effective healthcare1-3. To advance a personalized approach to healthcare, such biomarkers must reliably and accurately capture individual biology, predict biological age, and provide scalable and cost-effective measurements. We developed a novel approach - image-based chromatin and epigenetic age (ImAge) that captures intrinsic progressions of biological age, which readily emerge as principal changes in the spatial organization of chromatin and epigenetic marks in single nuclei without regression on chronological age. ImAge captured the expected acceleration or deceleration of biological age in mice treated with chemotherapy or following a caloric restriction regimen, respectively. ImAge from chronologically identical mice inversely correlated with their locomotor activity (greater activity for younger ImAge), consistent with the widely accepted role of locomotion as an aging biomarker across species. Finally, we demonstrated that ImAge is reduced following transient expression of OSKM cassette in the liver and skeletal muscles and reveals heterogeneity of in vivo reprogramming. We propose that ImAge represents the first-in-class imaging-based biomarker of aging with single-cell resolution.

Dynamic enhancer interactome promotes senescence and aging

Gene expression programs are regulated by enhancers which act in a context-specific manner, and can reside at great distances from their target genes. Extensive three-dimensional (3D) genome reorganization occurs in senescence, but how enhancer interactomes are reconfigured during this process is just beginning to be understood. Here we generated high-resolution contact maps of active enhancers and their target genes, assessed chromatin accessibility, and established one-dimensional maps of various histone modifications and transcription factors to comprehensively understand the regulation of enhancer configuration during senescence. Hyper-connected enhancer communities/cliques formed around genes that are highly expressed and within essential gene pathways in each cell state. In addition, motif analysis indicates the involvement of specific transcription factors in hyper-connected regulatory elements in each condition; importantly, MafK, a bZIP family transcription factor, was upregulated in senescence, and reduced expression of MafK ameliorated the senescence phenotypes. Because the accumulation of senescent cells is a key feature of aging, we further investigated enhancer connectomes in the liver of young and aged mice. Hyper-connected enhancer communities were identified during aging, which regulate essential genes that maintain cell differentiation and homeostasis. These findings reveal that hyper-connected enhancer communities correlate with high gene expression in senescence and aging and provide potential hotspots for therapeutic intervention in aging and age-associated diseases.

Abstract PR011: TXNRD1 drives innate immune response in senescent cells to promote tumor immune surveillance and age-associated inflammation

Cellular senescence regulates cancer and tissue aging in part through the secretion of proinflammatory factors known as the senescence-associated secretory phenotype (SASP). For example, sterile inflammation or ‘inflammaging’ is a hallmark of tissue aging. Thioredoxin reductase 1 (TXNRD1) genetic variability is associated with aging and is often upregulated in human cancers. TXNRD1’s role in regulating tissue aging and cancer has been attributed to its enzymatic role in regulating cellular redox. Here we show that TXNRD1 drives the SASP and inflammation through the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) innate immune response pathway independently of its enzymatic activity. TXNRD1 localizes to cytoplasmic chromatin fragments (CCF) and interacts with cGAS in a senescence status dependent manner, which is required for the SASP. Biochemically, TXNRD1 enhances the enzymatic activity of cGAS. TXNRD1 is required for both the tumor-promoting and immune-surveillance functions of senescent cells, which are mediated by the SASP in vivo in mouse tumor models. Treatment of aged mice with a TXNRD1 inhibitor that disrupts its interaction with cGAS, but not an inhibitor of its enzymatic activity alone, downregulated inflammaging in several tissues. In summary, our results report TXNRD1 promotes inflammation via activating the innate immune response in a manner depending on its interaction with cGAS but not its enzymatic activity. Our findings have important implications for both tissue aging and cancer.

Citation Format: Xue Hao, Bo Zhao, Martina Towers, Liping Liao, Hsin Yao Tang, Aaron Havas, Andrew V. Kossenkov, Shelley Berger, Peter D. Adams, David W. Speicher, Rugang Zhang. TXNRD1 drives innate immune response in senescent cells to promote tumor immune surveillance and age-associated inflammation [abstract]. In: Proceedings of the AACR Special Conference: Aging and Cancer; 2022 Nov 17-20; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_1):Abstract nr PR011.

The role of aging in cancer

Many cancers show an increase in incidence with age, and age is the biggest single risk factor for many cancers. However, the molecular basis of this relationship is poorly understood. Through a collection of review articles, our thematic issue discusses the link between aging and cancer in aspects including somatic mutations, proteostasis, mitochondria, metabolism, senescence, epigenetic regulation, immune regulation, DNA damage, and telomere function.

ADAR1 downregulation by autophagy drives senescence independently of RNA editing by enhancing p16INK4a levels

Cellular senescence plays a causal role in ageing and, in mice, depletion of p16INK4a-expressing senescent cells delays ageing-associated disorders1,2. Adenosine deaminases acting on RNA (ADARs) are RNA-editing enzymes that are also implicated as important regulators of human ageing, and ADAR inactivation causes age-associated pathologies such as neurodegeneration in model organisms3,4. However, the role, if any, of ADARs in cellular senescence is unknown. Here we show that ADAR1 is post-transcriptionally downregulated by autophagic degradation to promote senescence through p16INK4a upregulation. The ADAR1 downregulation is sufficient to drive senescence in both in vitro and in vivo models. Senescence induced by ADAR1 downregulation is p16INK4a-dependent and independent of its RNA-editing function. Mechanistically, ADAR1 promotes SIRT1 expression by affecting its RNA stability through HuR, an RNA-binding protein that increases the half-life and steady-state levels of its target mRNAs. SIRT1 in turn antagonizes translation of mRNA encoding p16INK4a. Hence, downregulation of ADAR1 and SIRT1 mediates p16INK4a upregulation by enhancing its mRNA translation. Finally, Adar1 is downregulated during ageing of mouse tissues such as brain, ovary and intestine, and Adar1 expression correlates with Sirt1 expression in these tissues in mice. Together, our study reveals an RNA-editing-independent role for ADAR1 in the regulation of senescence by post-transcriptionally controlling p16INK4a expression.

Abstract 2531: a

Hepatocellular carcinoma (HCC) is an emerging health crisis due to rapidly increasing incidence rates and an overall 5-year survival rate of 18%. Consequently, there is an urgent need for new therapies and better preventive strategies. Aging and obesity are two of the biggest risk factors for HCC, and with ever-increasing aging and obese populations, uncovering how aging and obesity drive the increased risk for HCC has become imperative. Aging and obesity are well known to be characterized by immune dysregulation leading to persistent inflammation, and a dysregulated immune microenvironment is also a common theme shared by multiple hallmarks of HCC. In this study, we aim to assess the immune microenvironment of aged and obese mouse livers by performing spatial phenotyping of distinct immune signatures which can potentially predispose hepatocytes to HCC. To address this, we used Akoya’s ultra-high multiplexed CODEX (CO-Detection by indEXing) imaging system to interrogate 31 different biomarkers in liver samples at the single cell level. Specifically, we compared the liver immune microenvironment of mice within 2 different treatment groups (old mice on a high fat diet (HFD) and young mice on a normal diet (ND)) to the immune landscape of liver tumor tissue. Our goal is to identify distinct immune phenotypes present in both, liver tumor tissues and livers of HFD mice, compared to ND livers - to better understand how immune dysregulation can predispose an aged and obese liver to HCC.

Citation Format: Adarsh Rajesh, Aaron Havas, Siva Karthik Varanasi, Katrina Evans, Bassem B. Cheikh, Clemens Duerrschmid, Najiba Mammadova, Peter Adams, Susan Kaech. a [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2531.

Efficacy of erythromycin acistrate (2'-acetyl erythromycin stearate) and erythromycin stearate in experimental infections in mice

The efficacy of erythromycin stearate (ES) and its 2'-acetyl ester (erythromycin acistrate, EA) was compared in eight experimental infections in mice of both sexes. In two studies the mice were made leukopenic by whole-body irradiation. Four absorption studies were also performed in parallel. In Streptococcus pneumoniae peritonitis, the protective dose 50% (PD50) value of EA and ES, given s.c., did not differ from each other. The bioavailability of EA was slightly inferior to that of ES. In three other peritonitis studies (2 Staphylococci and 1 Streptococcus), where the treatments were given s.c., EA seemed to lag behind ES in efficacy. The parallel absorption experiment showed, however, that, as compared to ES, only about one-half of EA was released from the s.c. injection site to the blood. The adjusted PD50 values of both erythromycins were about the same, with one exception. When the treatments were given i.p. both erythromycins were equally effective, and the difference in bioavailability was minor. On the contrary, the efficacy of 2'-ethylsuccinyl erythromycin was only about one-tenth that of the other erythromycins as was also the bioavailability. Oral treatment gave similar therapeutic results with EA and ES, with similar bioavailabilities, too. In the muscle abscess model, single s.c. injections of EA and ES were equally effective in reducing the growth of Staphylococcus aureus. These results suggest that there is no great difference in the in vivo antibacterial performance of ES and its 2'-acetyl ester, although the absorption problems complicate the interpretation. Hence EA performs better than expected if only the hydrolyzed drug were useful.

Studies on the nonspecific central nervous system effects of the novel antitussive compound vadocaine hydrochloride

Vadocaine hydrochloride (2',4'-dimethyl-6'-methoxy-3-(2-methylpiperidyl) propionanilide hydrochloride, OR K-242-HCl; INN: vadocaine) is a novel antitussive compound which is effective in several animal models at doses of 2.5-6 mg/kg. It has both central and peripheral local anaesthetizing properties. The present studies were aimed at exploring the specificity of the central antitussive activity of vadocaine. Vadocaine administered in doses of 25 and 50 mg/kg was not found to be effective in any of a series of experiments, although some antinociceptive activity was shown in the hotplate test and in the writhing test at a dose of 75 mg/kg. Some deteriorative activity was noted at a dose of 75 mg/kg in tests measuring motor coordination (rotarod) and spontaneous motility. This high dose of vadocaine did not affect pentobarbital sodium-induced sleeping time nor protect the animal from pentetrazole-induced convulsions. As expected, codeine phosphate was found to be a more potent antinociceptive drug than vadocaine, also enhancing spontaneous motility. Both the control anaesthetics benzonatate and lidocaine proved rather ineffective. Benzonatate (50 mg/kg) did not alter any of the results, whereas lidocaine (50 mg/kg) caused a decrease in the number of writhings. In conclusion, vadocaine can be said to initiate minor deterioration of the central nervous system only at doses about 10 times higher than those which show antitussive activity. Acute lethal doses are still 2 to 5 times higher. The central antitussive action of vadocaine can therefore be considered fairly specific.

Skin irritation by dithranol (anthralin) and its 10-acyl analogues in 3 animal models

The skin irritant properties of a single application of dithranol (anthralin), a typical "delayed irritant", and its 10-acyl analogues in acetone or white petrolatum were compared in 3 animals models. Maximal irritation was reached at about 24 h in mouse ear, 48 h in guinea pig back and 1 week in miniature swine back, the last-mentioned serving as a good model of human skin. In all animal species, butantrone was significantly less irritant than dithranol, 10-acetyl dithranol or 10-propionyl dithranol. 10-acetyl dithranol was the most irritant compound. Clinical trials with butantrone on psoriasis are justified.