👤 Jorge Gracia-Sancho

Aging and alcohol misuse independently alter monocyte (MO) and macrophage (MØ) function, leading to impaired antimicrobial responses. However, how alcohol misuse contributes to impaired MO/MØ function during aging remains unclear. We compared the transcriptomes of MOs and MØs from alcohol-modulated niches (liver, brain, and bone marrow [BM]) in young (3-month-old) and old (20-24-month-old) female C57BL/6N mice (n = 4-6 per group). Statistical significance was determined using two-way ANOVA. MO/MØ transcriptomes showed unique organ-specific responses to aging and alcohol. Aging elicited a common deregulation of pathogen-responsive pathways, while alcohol misuse commonly inhibited IFN signaling in the aged populations. Our studies on intercellular communication using ligand-receptor interactions revealed that BM MOs were the least communicative and liver MØs were the most communicative. Alcohol misuse specifically increased MO/MØ communication in aging. We also identified and validated specific pathways driving inter-organ MO/MØ crosstalk in alcohol misuse during aging, including APOE-TREM2 signaling from the liver to microglia and the NRXN2 and SPP1 pathways. Our results provide a unique insight into the heterogeneity of the MO/MØ transcriptome and define the inter-organ crosstalk between BM, liver, and brain during aging and alcohol misuse. Aging and alcohol misuse are linked to immune dysfunction, systemic inflammation, and altered innate immune responses. Here, we examined monocyte/macrophage responses in the liver, brain, and bone marrow of young and aged mice under alcohol exposure at the transcriptomic level. We observed that aging and alcohol predominantly elicited organ-specific changes in gene expression, with minimal overlap between the monocyte/macrophage populations across different tissues. However, aging commonly upregulated pathogen response pathways while alcohol misuse inhibited interferon signaling. We also assessed cell-cell communication by analyzing ligand-receptor expression in the different monocyte/macrophage populations and identified candidate molecules (APOE, TREM2, NRXN2, SPP1) from the top pathways guiding inter-organ signaling specifically in aging and alcohol misuse. Our findings have generated a unique repository and provide novel insights on how aging and alcohol impact tissue-specific monocytes/macrophages and their crosstalk. Show less

In non-alcoholic steatohepatitis (NASH), the function of urea cycle enzymes (UCEs) may be affected, resulting in hyperammonemia and the risk of disease progression. We aimed to determine whether the expression and function of UCEs are altered in an animal model of NASH and in patients with non-alcoholic fatty liver disease (NAFLD), and whether this process is reversible. Rats were first fed a high-fat, high-cholesterol diet for 10 months to induce NASH, before being switched onto a normal chow diet to recover. In humans, we obtained liver biopsies from 20 patients with steatosis and 15 with NASH. Primary rat hepatocytes were isolated and cultured with free fatty acids. We measured the gene and protein expression of ornithine transcarbamylase (OTC) and carbamoylphosphate synthetase (CPS1), as well as OTC activity, and ammonia concentrations. Moreover, we assessed the promoter methylation status of OTC and CPS1 in rats, humans and steatotic hepatocytes. In NASH animals, gene and protein expression of OTC and CPS1, and the activity of OTC, were reversibly reduced. Hypermethylation of Otc promoter genes was also observed. Additionally, in patients with NAFLD, OTC enzyme concentration and activity were reduced and ammonia concentrations were increased, which was further exacerbated in those with NASH. Furthermore, OTC and CPS1 promoter regions were hypermethylated. In primary hepatocytes, induction of steatosis was associated with Otc promoter hypermethylation, a reduction in the gene expression of Otc and Cps1, and an increase in ammonia concentration in the supernatant. NASH is associated with a reduction in the gene and protein expression, and activity, of UCEs. This results in hyperammonemia, possibly through hypermethylation of UCE genes and impairment of urea synthesis. Our investigations are the first to describe a link between NASH, the function of UCEs, and hyperammonemia, providing a novel therapeutic target. In patients with fatty liver disease, the enzymes that convert nitrogen waste into urea may be affected, leading to the accumulation of ammonia, which is toxic. This accumulation of ammonia can lead to scar tissue development, increasing the risk of disease progression. In this study, we show that fat accumulation in the liver produces a reversible reduction in the function of the enzymes that are involved in detoxification of ammonia. These data provide potential new targets for the treatment of fatty liver disease. Show less

The Kruppel-like factor 2 (KLF2) and Kruppel-like factor 4 (KLF4) transcription factors have recently been shown to act as critical regulators of endothelial homeostasis. While several insights have been made into the signaling mechanisms orchestrating endothelial KLF2 expression, those governing the expression of KLF4 in the vascular endothelium remain largely unknown. Here, we show that diverse vasoprotective stimuli including an atheroprotective shear stress waveform, simvastatin, and resveratrol induce the expression of KLF4 in cultured human endothelial cells. We further demonstrate that the induction of KLF4 by resveratrol and atheroprotective shear stress occurs via a MEK5/MEF2-dependent signaling pathway. Since MEK5 activation is also critical for the expression of KLF2, we assessed the individual contribution of KLF4 and KLF2 to the global transcriptional activity triggered by MEK5 activation. Genome-wide transcriptional profiling of endothelial cells overexpressing KLF4, KLF2, or constitutively active MEK5 revealed that 59.2% of the genes regulated by the activation of MEK5 were similarly controlled by either KLF2 or KLF4. Collectively, our data identify a significant degree of mechanistic and functional conservation between KLF2 and KLF4, and importantly, provide further insights into the complex regulatory networks governing endothelial vasoprotection. Show less

Resveratrol activates Sirtuin 1 (SIRT1), a nicotinamide adenine dinucleotide-dependent deacetylase which modulates metabolic homeostasis and improves several pathophysiological features present in diseases of ageing. In particular, it has been shown that SIRT1 activation improves endothelial dysfunction and suppresses vascular inflammation, two central pathophysiological processes involved in the initiation and progression of cardiovascular disease. The downstream targets of SIRT1 activation in this context, however, remain poorly defined. Therefore, in this study, we aimed to characterize mechanistically how SIRT1 activation regulates the endothelial vasoprotective phenotype. We demonstrate that SIRT1 activation by resveratrol increases the expression of the transcription factor Krüppel-like factor 2 (KLF2) in human vascular endothelial cells, resulting in the orchestrated regulation of transcriptional programs critical for conferring an endothelial vasoprotective phenotype. Moreover, we show that KLF2 upregulation by resveratrol occurs via a mitogen-activated protein kinase 5/myocyte enhancing factor 2-dependent signalling pathway. Collectively, these observations provide a new mechanistic framework to understand the vascular protective effects mediated by SIRT1 activators and define KLF2 as a critical mediator of these effects. Show less