Tissue-specific Sources Research Articles

Abstract 10765: Plasma Cell-Free DNA Predicts Survival and Maps Tissue-Specific Sources of Injury in Pulmonary Arterial Hypertension

Background: Cell-free DNA (cfDNA) is a non-invasive marker of tissue injury. Although being incrementally used as a clinical biomarker, its significance in pulmonary arterial hypertension (PAH) is unknown. Methods: Plasma cfDNA was isolated in two independent PAH cohorts (A, n=48; B, n=161) and healthy controls (n=48). Clinical variables and survival status were collected for Registry to Evaluate Early And Long-term PAH Disease Management (REVEAL 2.0) scores and outcome determinations. Total cfDNA levels were compared amongst controls and PAH patients and also used to predict transplant-free survival. A subset of samples from cohort B (n=96) and controls (n=16) were subjected to bisulfite sequencing and methylation analysis to quantify tissue-specific sources of cfDNA. Results: Median (IQR) cfDNA concentrations were higher in cohort A PAH patients (exploratory cohort) compared to controls and increased according to REVEAL 2.0 risk group: controls 13.7 (10.8-18.8) vs low risk 14.4 (10.0-19.9) vs medium risk 14.6 (11.3-28.2) vs high risk 31.5 (17.2-45.6) ng/ml (P<0.01). cfDNA analysis in cohort B (validation cohort) demonstrated a similar cfDNA pattern: controls 13.7 (10.8-18.8) vs low risk 24.3 (16.0-57.9) vs medium risk 50.4 (29.4-70.9) vs high risk 51.5 (34.0-110.5) ng/ml (P<0.0001). cfDNA tertiles (Log-Rank; P=0.0001) and REVEAL 2.0 risk group (Log-Rank; P<0.0001) similarly predicted transplant-free survival, and the addition of cfDNA to REVEAL 2.0 improved model performance (AUC 0.64 to 0.70; P<0.05). Tissue-specific methylation analysis revealed increased cfDNA originating from vascular endothelium, cardiac myocytes, monocytes, erythrocyte progenitors, neutrophils, natural killer cells, and adipocytes (all P<0.005), but not colon, head/neck, liver, bladder, or kidney. With the exception of natural killer cells, cfDNA from enriched tissues also differentiated PAH patients of varying REVEAL 2.0 risk. Conclusions: cfDNA is elevated in PAH patients, correlates with disease severity and predicts worse survival. Methylation analysis of cfDNA in PAH patients is consistent with prevailing paradigms of disease pathogenesis. Thus, cfDNA may add prognostic power to PAH risk assessment and provide insight into disease progression.

PMN-derived netrin-1 attenuates cardiac ischemia-reperfusion injury via myeloid ADORA2B signaling.

Previous studies implicated the neuronal guidance molecule netrin-1 in attenuating myocardial ischemia-reperfusion injury. However, the tissue-specific sources and receptor signaling events remain elusive. Neutrophils are among the first cells responding to an ischemic insult and can be associated with tissue injury or rescue. We found netrin-1 levels were elevated in the blood of patients with myocardial infarction, as well as in mice exposed to myocardial ischemia-reperfusion. Selectively increased infarct sizes and troponin levels were found in Ntn1loxP/loxP Lyz2 Cre+ mice, but not in mice with conditional netrin-1 deletion in other tissue compartments. In vivo studies using neutrophil depletion identified neutrophils as the main source for elevated blood netrin-1 during myocardial injury. Finally, pharmacologic studies using treatment with recombinant netrin-1 revealed a functional role for purinergic signaling events through the myeloid adenosine A2b receptor in mediating netrin-1-elicited cardioprotection. These findings suggest an autocrine signaling loop with a functional role for neutrophil-derived netrin-1 in attenuating myocardial ischemia-reperfusion injury through myeloid adenosine A2b signaling.

Decreased body weight and hepatic steatosis with altered fatty acid ethanolamide metabolism in aged L-Fabp−/− mice

The tissue-specific sources and regulated production of physiological signals that modulate food intake are incompletely understood. Previous work showed that L-Fabp(-/-) mice are protected against obesity and hepatic steatosis induced by a high-fat diet, findings at odds with an apparent obesity phenotype in a distinct line of aged L-Fabp(-/-) mice. Here we show that the lean phenotype in L-Fabp(-/-) mice is recapitulated in aged, chow-fed mice and correlates with alterations in hepatic, but not intestinal, fatty acid amide metabolism. L-Fabp(-/-) mice exhibited short-term changes in feeding behavior with decreased food intake, which was associated with reduced abundance of key signaling fatty acid ethanolamides, including oleoylethanolamide (OEA, an agonist of PPARα) and anandamide (AEA, an agonist of cannabinoid receptors), in the liver. These reductions were associated with increased expression and activity of hepatic fatty acid amide hydrolase-1, the enzyme that degrades both OEA and AEA. Moreover, L-Fabp(-/-) mice demonstrated attenuated responses to OEA administration, which was completely reversed with an enhanced response after administration of a nonhydrolyzable OEA analog. These findings demonstrate a role for L-Fabp in attenuating obesity and hepatic steatosis, and they suggest that hepatic fatty acid amide metabolism is altered in L-Fabp(-/-) mice.