New age-related mechanisms of atherosclerosis and immune cell dysfunction: role of LMNA and PPM1D

• Autores: Marta Amorós Pérez
• Directores de la Tesis: Vicente Andrés García (dir. tes.), José Javier Fuster Ortuño (dir. tes.)
• Lectura: En la Universidad Autónoma de Madrid ( España ) en 2024
• Idioma: español
• Número de páginas: 228
• Títulos paralelos:
  • Nuevos mecanismos de aterosclerosis y disfunción de células inmunes ligados al envejecimiento: el papel de LMNA y PPM1D
• Enlaces
  • Tesis en acceso abierto en: Biblos-e Archivo
• Resumen

  • Aging is the major risk factor for cardiovascular and cerebrovascular disease (CVD), in part due to the cumulative exposure to traditional cardiovascular risk factors such as hypercholesterolemia. However, clinical and epidemiological evidence suggest the existence of yet unidentified risk factors that contribute to age-dependent CVD. Previous research from our laboratory demonstrates that the levels of Lamin A/C, one of the main components of the nuclear envelope, decrease in circulating leukocytes during aging in both humans and mice, and that Lamin A/C deficiency in immune cells leads to accelerated atherosclerosis in mice. Our laboratory has also provided extensive experimental data supporting that clonal hematopoiesis (CH) driven by somatic mutations is a new risk factor for CVD. PPM1D encodes for a protein phosphatase that negatively regulates the DNA damage repair pathway and is among the most commonly mutated genes in CH. Truncating PPM1D gain-of-function mutations are relatively frequent in elderly individuals, and are particularly enriched in cancer survivors, a phenomenon termed therapy-related CH (t-CH). Our previous sequencing studies in humans demonstrate an association between PPM1D mutations and an increased risk of coronary and peripheral artery disease, but the mechanism underlying this association remains unexplored. Based on these previous findings, we hypothesized that age-related downregulation of Lamin A/C in immune cells, and CH driven by somatic PPM1D mutations constitute two emerging age-dependent CVD risk factors. To test this hypothesis, we used in this doctoral thesis different mouse models and bone marrow transplant strategies to specifically modify the hematopoietic cell compartment. To study the role of Lamin A in atherosclerosis, we have generated a new transgenic mouse model with inducible Lamin A overexpression and demonstrated that hematopoietic cell-specific Lamin A overexpression is associated with decreased atherosclerosis development in Ldlr-/- mice, mainly due to decreased leukocyte infiltration within the artery wall. These results were further validated by sc-RNAseq analysis of atherosclerotic aortas from mice with hematopoietic Lamin A deficiency and overexpression, highlighting an important role of Lamin A/C in atherosclerosis development, mediated at least in part through regulation of leukocyte extravasation. To address the role of CH-driven by PPM1D mutations in atherosclerosis, we have generated a novel mouse model of radiation therapy-related CH driven by Ppm1d mutations by using a non-invasive adoptive transfer strategy to generate chimeric Ldlr-/- mice carrying hematopoietic cells with the truncating Ppm1d(R451X) mutation. Notably, Ppm1d mutant cells expanded in blood and bone marrow (BM) to outcompete normal cells after exposure to radiation therapy, reaching approximately 20% chimerism in blood, comparable to the human scenario. Nevertheless, no effect on hypercholesterolemia-induced atherosclerosis development was observed regardless of BM genotype or treatment. These results were corroborated by using conventional bone marrow transplant strategies to generate chimeric Ldlr-/- mice carrying heterozygous and homozygous Ppm1d(R451X) mutations. In contrast, in a mouse model of atherosclerosis regression based on adenovirus-mediated LDLR recue we found that carrying heterozygous Ppm1d(R451X) mutations impairs the beneficial atherosclerotic plaque remodeling induced by cholesterol lowering. Collectively, our results support the notion that the age-dependent downregulation of Lamin A/C in immune cells and CH-driven by PPM1D mutations are new age-related mechanisms that contribute to atherosclerosis and immune cell dysfunction