Determination of a microRNA signature of protective kidney ischemic preconditioning originating from proximal tubules

Ischemic preconditioning (IPC) is effective in limiting subsequent ischemic acute kidney injury in experimental models. MicroRNAs are an important class of post-transcriptional regulator and show promise as biomarkers of kidney injury. We evaluated the time- and dose-dependence of benefit from IPC in a rat model of functional (bilateral) ischemia–reperfusion injury (IRI). We found optimal protection from subsequent injury following short, repetitive sequences of preconditioning insult. We subsequently used hybridization array and microRNA sequencing to characterize microRNA signatures of protective IPC and of IRI. These approaches identified a profile of microRNA changes consequent on IRI, that were limited by prior IPC. To localize these signals within the kidney, we used laser capture microdissection and RT-qPCR to measure microRNA abundance in nephron segments, pinpointing microRNA changes principally to glomeruli and proximal tubules. Our data describe a unique microRNA signature for IRI in the rat kidney. Pulsatile IPC reduces kidney damage following IRI and diminishes this microRNA signal. We have also identified candidate microRNAs that may act as biomarkers of injury and therapeutic targets in this context

Association Between Clonal Hematopoiesis Driver Mutations, Immune Cell Function, and the Vasculometabolic Complications of Obesity

Background Obesity is accompanied by dysregulated inflammation, which can contribute to vasculometabolic complications including metabolic syndrome and atherosclerosis. Recently, clonal hematopoiesis of indeterminate potential (CHIP) has emerged as a risk factor for cardiovascular diseases. We aimed to determine how CHIP is related to immune cell function, systemic inflammation, and vasculometabolic complications in obese individuals. Methods and Results Two hundred ninety‐seven individuals with overweight and obesity, between the ages of 54 and 81 years, were recruited in a cross‐sectional study. Clonal hematopoiesis driver mutations (CHDMs) were identified with an ultrasensitive targeted assay. Assessment of carotid artery atherosclerosis was performed with ultrasound. Detailed immunological parameters, including cytokine production capacity of peripheral blood mononuclear cells, and targeted plasma proteomics analysis, were studied. Adipose tissue inflammation was determined in subcutaneous fat biopsies. Individuals with CHIP had higher concentrations of circulating IL (interleukin)‐6. Total number of leukocytes and neutrophils were higher in individuals with CHIP. In contrast, ex vivo cytokine production capacity of peripheral blood mononuclear cells was significantly lower in individuals with CHIP. Sex‐stratified analysis showed that men with CHDMs had significantly higher leukocyte and neutrophil counts, and ex vivo cytokine production capacity was lower in women with CHDMs. Surprisingly, the presence of atherosclerotic plaques was significantly lower in individuals with CHDMs. There was no relation between CHIP and metabolic syndrome. Conclusions In individuals with overweight or obesity, CHDMs are not associated with vasculometabolic complications, but rather with a lower presence of carotid plaques. CHDMs associate with increased circulating inflammatory markers and leukocyte numbers, but a lower peripheral blood mononuclear cell cytokine production capacity

Clonal Hematopoiesis has Prognostic Value in Dilated Cardiomyopathy independent of Age and Clone Size

BACKGROUND: Clonal hematopoiesis (CH) gives rise to mutated leukocyte clones that induce cardiovascular inflammation, and thereby impact the disease course in atherosclerosis and ischemic heart failure. Clonal hematopoiesis of indeterminate potential (CHIP) refers to a variant allele frequency (VAF; a marker for clone size) in blood of =2%. The impact of CH clones -including small clone sizes (VAF<0.5%)- in non-ischemic dilated cardiomyopathy (DCM) remains largely undetermined. OBJECTIVES: To establish the prognostic impact of CH in DCM including small clones. METHODS: CH is determined using an ultrasensitive single-molecule Molecular Inversion Probe technique that allows detection of clones down to a VAF of 0.01%. Cardiac death and all-cause mortality were analyzed using receiver operating characteristic curve-optimized VAF cut-off values. RESULTS: Five hundred twenty DCM patients have been included. One hundred and nine patients (21%) had CH driver mutations, of which 45 had a VAF of =2% and 31 <0.5%. The median follow-up duration is 6.5 years [interquartile range 4.7-9.7]. DCM patients with CH have a higher risk of cardiac death (HR 2.33 using a VAF cut-off of 0.36%, 95% confidence interval 1.24-4.40) and all-cause mortality (HR 1.72 using a VAF cut-off of 0.06%, 95% confidence interval 1.10-2.69), independent of age, sex, left ventricle ejection fraction and New York Heart Association classification. CONCLUSION: CH predicts cardiac death and all-cause mortality in DCM patients with an optimal threshold for clone size of 0.36% and 0.06%, respectively. Therefore, CH is prognostically relevant independent of clone size in patients with DCM

Peripheral blood mononuclear cell hyperresponsiveness in patients with premature myocardial infarction without traditional risk factors

Summary: An increasing number of patients develop an atherothrombotic myocardial infarction (MI) in the absence of standard modifiable risk factors (SMuRFs). Monocytes and macrophages regulate the development of atherosclerosis, and monocytes can adopt a long-term hyperinflammatory phenotype by epigenetic reprogramming, which can contribute to atherogenesis (called “trained immunity”). We assessed circulating monocyte phenotype and function and specific histone marks associated with trained immunity in SMuRFless patients with MI and matched healthy controls. Even in the absence of systemic inflammation, monocytes from SMuRFless patients with MI had an increased overall cytokine production capacity, with the strongest difference for LPS-induced interleukin-10 production, which was associated with an enrichment of the permissive histone marker H3K4me3 at the promoter region. Considering the lack of intervenable risk factors in these patients, trained immunity could be a promising target for future therapy

Activation of naïve CD4+ T cells re-tunes STAT1 signaling to deliver unique cytokine responses in memory CD4+ T cells

The cytokine IL-6 controls the survival, proliferation and effector characteristics of lymphocytes through activation of the transcription factors STAT1 and STAT3. While STAT3 activity is an ever-present feature of IL-6 signaling in CD4+ T cells, prior activation via the T cell antigen receptor limits IL-6’s control of STAT1 in effector and memory populations. Here we found that phosphorylation of STAT1 in response to IL-6 was regulated by the tyrosine phosphatases PTPN2 and PTPN22 expressed in response to the activation of naïve CD4+ T cells. Transcriptomics and chromatin immunoprecipitation–sequencing (ChIP-seq) of IL-6 responses in naïve and effector memory CD4+ T cells showed how the suppression of STAT1 activation shaped the functional identity and effector characteristics of memory CD4+ T cells. Thus, tyrosine phosphatases induced by the activation of naïve T cells determine the way activated or memory CD4+ T cells sense and interpret cytokine signals