Damage to Nuclear and Mitochondrial DNA in Different Organs in Streptozotocin-Induced Diabetes Models in BALB/c Mice

DNA-PKcs-Driven YAP1 Phosphorylation and Nuclear Translocation: a Key Regulator of Ferroptosis in Hyperglycemia-Induced Cardiac Dysfunction in Type 1 Diabetes

The DNA-Dependent Protein Kinase catalytic subunit (DNA-PKcs) acts as a principal executor in the DNA damage response (DDR), mediating the phosphorylation of a broad spectrum of substrates integral to DNA repair and apoptosis. This investigation seeks to discern the possible association and mechanisms linking hyperglycemia-induced ferroptosis and DNA-PKcs in DCM. This data exhibits a substantial activation of DNAPKcs- dependent DDR in mice with streptozotocin-induced DCM. However, deletion of DNA-PKcs in cardiomyocytes notably mitigates DNA damage, enhances heart function and dampens the inflammatory response. Co-IP/MS analysis and subsequent validation experiments demonstrate that DNA-PKcs directly interacts with and phosphorylates YAP1 at Thr226. This phosphorylation event facilitates the nuclear retention of YAP1, where it intensifies the transcription of ferroptosis-associated genes. Knockin mice expressing a nonphosphorylatable T226A YAP1 mutant display decreased ferroptosis, reduced myocardial fibrosis and improved heart function. Taken together, this study unravels that DDR acts as an intracellular stress damage sensor, perceiving hyperglycemic conditions and subsequently transmitting the damage signal to incite ferroptosis through the interplay between DNA-PKcs and YAP1. This novel insight suggests that the DNA-PKcs-mediated YAP1 phosphorylation and the ferroptosis activation could be the promising therapeutic targets for the management of DCM.

Long-range PCR as a tool for evaluating mitochondrial DNA damage: Principles, benefits, and limitations of the technique

Mitochondrial DNA (mtDNA) is often more susceptible to damage compared to nuclear DNA. This is due to its localization in the mitochondrial matrix, where a large portion of reactive oxygen species are produced. Mitochondria do not have histones and mtDNA is only slightly protected by histone-like proteins and is believed to have less efficient repair mechanisms. In this review, we discuss the long-range PCR method, which allows for the effective detection of mtDNA damage. The method is based on the assumption that various types of DNA lesions can interfere the progress of DNA polymerase, resulting in reduced amplification efficiency. It can be used to estimate the number of additional (above background) lesions in mtDNA. The review outlines the evolution of the methodology, its variations, applications in a wide range of model organisms, the advantages of the method and its limitations, as well as ways to overcome these limitations. Over the past two decades, the use of long-range PCR has allowed the study of mtDNA repair mechanisms, the characteristics of mitochondrial genome damage in various neurodegenerative diseases, aging, ischemic and oncological processes, as well as in anticancer therapy. The assessment of mtDNA damage has also been proposed for use in environmental biomonitoring. This review provides a critical evaluation of the various variations of this method, summarizes the accumulated data, and discusses the role of mtDNA damage in different organs at the organismal level.

Mitofusin 1 silencing decreases the senescent associated secretory phenotype, promotes immune cell recruitment and delays melanoma tumor growth after chemotherapy

Cellular senescence is a therapy endpoint in melanoma, and the senescence-associated secretory phenotype (SASP) can affect tumor growth and microenvironment, influencing treatment outcomes. Metabolic interventions can modulate the SASP, and mitochondrial energy metabolism supports resistance to therapy in melanoma. In a previous report we showed that senescence, induced by the DNA methylating agent temozolomide, increased the level of fusion proteins mitofusin 1 and 2 in melanoma, and silencing Mfn1 or Mfn2 expression reduced interleukin-6 secretion by senescent cells. Here we expanded these observations evaluating the secretome of senescent melanoma cells using shotgun proteomics, and explored the impact of silencing Mfn1 on the SASP. A significant increase in proteins reported to reduce the immune response towards the tumor was found in the media of senescent cells. The secretion of several of these immunomodulatory proteins was affected by Mfn1 silencing, among them was galectin-9. In agreement, tumors lacking mitofusin 1 responded better to treatment with the methylating agent dacarbazine, tumor size was reduced and a higher immune cell infiltration was detected in the tumor. Our results highlight mitochondrial dynamic proteins as potential pharmacological targets to modulate the SASP in the context of melanoma treatment.