Reduced brain UCP2 expression mediated by microRNA-503 contributes to increased stroke susceptibility in the high-salt fed stroke-prone spontaneously hypertensive rat

Abstract

UCP2 maps nearby the lod score peak of STR1-stroke QTL in the SHRSP rat strain. We explored the potential contribution of UCP2 to the high-salt diet (JD)-dependent increased stroke susceptibility of SHRSP. Male SHRSP, SHRSR, two reciprocal SHRSR/SHRSP-STR1/QTL stroke congenic lines received JD for 4 weeks to detect brain UCP2 gene/protein modulation as compared with regular diet (RD). Brains were also analyzed for NF-κB protein expression, oxidative stress level and UCP2-targeted microRNAs expression level. Next, based on knowledge that fenofibrate and Brassica Oleracea (BO) stimulate UCP2 expression through PPARα activation, we monitored stroke occurrence in SHRSP receiving JD plus fenofibrate versus vehicle, JD plus BO juice versus BO juice plus PPARα inhibitor. Brain UCP2 expression was markedly reduced by JD in SHRSP and in the (SHRsr.SHRsp-(D1Rat134-Mt1pa)) congenic line, whereas NF-κB expression and oxidative stress level increased. The opposite phenomenon was observed in the SHRSR and in the (SHRsp.SHRsr-(D1Rat134-Mt1pa)) reciprocal congenic line. Interestingly, the UCP2-targeted rno-microRNA-503 was significantly upregulated in SHRSP and decreased in SHRSR upon JD, with consistent changes in the two reciprocal congenic lines. Both fenofibrate and BO significantly decreased brain microRNA-503 level, upregulated UCP2 expression and protected SHRSP from stroke occurrence. In vitro overexpression of microRNA-503 in endothelial cells suppressed UCP2 expression and led to a significant increase of cell mortality with decreased cell viability. Brain UCP2 downregulation is a determinant of increased stroke predisposition in high-salt-fed SHRSP. In this context, UCP2 can be modulated by both pharmacological and nutraceutical agents. The microRNA-503 significantly contributes to mediate brain UCP2 downregulation in JD-fed SHRSP.

Uncoupling Protein 2: A Key Player and a Potential Therapeutic Target in Vascular Diseases

“…Similar findings were more recently obtained in the brain of the SHRSP, compared to the SHRSR, with evidence of a significant contributory role of reduced UCP2 gene and protein expression in the higher stroke predisposition of the strain [ 74 ].…”

“…Thus, HS diet, high BP levels, and ageing are able to turn off tissue UCP2 gene expression only in the SHRSP animal model through still unexplained mechanisms, therefore contributing to the higher susceptibility to vascular disease of the strain. Interestingly, an epigenetic regulation may be involved in the selective UCP2 gene downregulation upon HS diet in SHRSP, as suggested by the evidence obtained in our studies in relation to both kidney injury [ 71 ] and brain damage [ 74 ]. Based on the above-reported evidence, an increase in UCP2 expression may play a compensatory role to offset, at least in part, the salt-induced endothelial dysfunction and vascular damage in hypertension with a consequent net reduction of adverse outcomes.…”

“…Moreover, a striking downregulation of UCP2 gene and protein expression was found in relation to both hypertension and ageing in the brain, heart, and kidneys of the SHRSP, but not of the SHRSR [ 74 ]. In fact, the age- and hypertension-related UCP2 suppression in SHRSP associated with a higher oxidative stress accumulation and inflammation in all tissues examined, along with an increased rate of interstitial, perivascular, peritubular, and glomerular fibrosis in the kidneys; with increased percentage of perivascular and myocardial interstitial collagen accumulation in the heart; and with higher occurrence of ischemic and hemorrhagic lesions in the brain [ 75 ].…”

Pathogenesis of Ischemic Stroke: Role of Epigenetic Mechanisms

“…UCP2 is a mitochondrial anion carrier protein that exerts an antioxidant effect in several tissues [83]. High-salt diet fed SHRSP showed a significant upregulation of brain miR-503 level compared to the control strain, the stroke resistant spontaneously hypertensive rat (SHRSR), with a consequent decrease of brain UCP2 expression and increased stroke occurrence [17].…”

“…Several case-control association studies revealed the contributory role of single nucleotide polymorphisms (SNPs) belonging to key hormonal and molecular systems including: the renin-angiotensin-aldosterone system (RAAS) [8], the natriuretic peptides family [9], the hemostasis and coagulation cascade [10,11], the lipoprotein metabolism [12], inflammation [13,14], homocysteine metabolism [15]. Our group has demonstrated that genes encoding proteins of the mitochondrial electron transport chain are key elements to guarantee correct mitochondrial function, cell viability and protection from stroke occurrence [16][17][18][19][20]. Genome-wide association studies confirmed the existence of several variants belonging to different genes associated with IS and their specific subtypes, such as paired-like homeodomain transcription factor 2 (PITX2) and Zinc Finger Homeobox 3 (ZFHX3) in Although several studies have investigated the molecular and genetic mechanisms underlying the pathogenesis of stroke, additional mechanisms still remain to be elucidated.…”