OBJECTIVE:20-Hydroxyeicosatetraenoic acid (20-HETE) is a vasoactive eicosanoid exhibiting effects on vascular smooth muscle cell (VSMC) via G-protein coupled receptor 75 (GPR75) and include stimulation of contractility, migration, and growth. We examined whether VSMC-targeted overexpression of CYP4A12, the primary 20-HETE-producing enzyme in mice, is sufficient to promote hypertension.METHODS:Mice with VSM-specific Cyp4a12 overexpression (Myh11-4a12) and their littermate controls (WT) were generated by crossbreeding Cyp4a12-floxed with Myh11-Cre mice. The 20-HETE receptor blocker, N-disodium succinate-20-hydroxyeicosa-6(Z),15(Z)-diencarboxamide (AAA), was administered in the drinking water. Experiments were carried out for 12 days. SBP was measured by tail cuff. Renal interlobar and mesenteric arteries were harvested for assessment of gene expression, 20-HETE levels, vascular contractility, vasodilation, and remodeling.RESULTS:Vascular and circulatory levels of 20-HETE were several folds higher in Myh11-4a12 mice compared with WT. The Myh11-4a12 mice compared with WT were hypertensive (145 ± 2 vs. 127 ± 2 mmHg; P < 0.05) and their vasculature displayed a contractile phenotype exemplified by increased contractility, reduced vasodilatory capacity, and increased media to lumen ratio. All these features were reversed by the administration of AAA. The mechanism of increased contractility includes, at least in part, Rho-kinase activation followed by increased myosin light chain phosphorylation and activation of the contractile apparatus.CONCLUSION:VSM-specific Cyp4a12 overexpression is sufficient to alter VSM cell phenotype through changes in contractile markers and enhancement in contractility that promote hypertension and vascular dysfunction in a 20-HETE-dependent manner. The 20-HETE receptor GPR75 may represent a novel target for the treatment of hypertension and associated vascular conditions.

The authors regret to have made a mistake in the labelling of the y-axis in Fig. 1B and Figure VIB, Supplement. The y-axis should be in ng/mg protein. Also, the text of the corresponding figure legends as well as the text of Table 1, Supplement should read ng/mg protein instead of pg/mg protein. The authors would like to apologise for any inconvenience caused. Elevated 20-HETE in metabolic syndrome regulates arterial stiffness and systolic hypertension via MMP12 activationJournal of Molecular and Cellular CardiologyVol. 117PreviewArterial stiffness plays a causal role in development of systolic hypertension. 20-hydroxyeicosatetraeonic acid (20-HETE), a cytochrome P450 (CYP450)-derived arachidonic acid metabolite, is known to be elevated in resistance arteries in hypertensive animal models and loosely associated with obesity in humans. However, the role of 20-HETE in the regulation of large artery remodeling in metabolic syndrome has not been investigated. We hypothesized that elevated 20-HETE in metabolic syndrome increases matrix metalloproteinase 12 (MMP12) activation leading to increased degradation of elastin, increased large artery stiffness and increased systolic blood pressure. Full-Text PDF

Arterial stiffness plays a causal role in development of systolic hypertension. 20-hydroxyeicosatetraeonic acid (20-HETE), a cytochrome P450 (CYP450)-derived arachidonic acid metabolite, is known to be elevated in resistance arteries in hypertensive animal models and loosely associated with obesity in humans. However, the role of 20-HETE in the regulation of large artery remodeling in metabolic syndrome has not been investigated. We hypothesized that elevated 20-HETE in metabolic syndrome increases matrix metalloproteinase 12 (MMP12) activation leading to increased degradation of elastin, increased large artery stiffness and increased systolic blood pressure. 20-HETE production was increased ~7 fold in large, conduit arteries of metabolic syndrome (JCR:LA-cp, JCR) vs. normal Sprague-Dawley (SD) rats. This correlated with increased elastin degradation (~7 fold) and decreased arterial compliance (~75% JCR vs. SD). 20-HETE antagonists blocked elastin degradation in JCR rats concomitant with blocking MMP12 activation. 20-HETE antagonists normalized, and MMP12 inhibition (pharmacological and MMP12-shRNA-Lnv) significantly improved (~50% vs. untreated JCR) large artery compliance in JCR rats. 20-HETE antagonists also decreased systolic (182 ± 3 mmHg JCR, 145 ± 3 mmHg JCR + 20-HETE antagonists) but not diastolic blood pressure in JCR rats. Whereas diastolic pressure was fully angiotensin II (Ang II)-dependent, systolic pressure was only partially Ang II-dependent, and large artery stiffness was Ang II-independent. Thus, 20-HETE-dependent regulation of systolic blood pressure may be a unique feature of metabolic syndrome related to high 20-HETE production in large, conduit arteries, which results in increased large artery stiffness and systolic blood pressure. These findings may have implications for management of systolic hypertension in patients with metabolic syndrome.

Large artery stiffness is a causal factor in development of systolic hypertension. 20-hydroxyeicosatetraeonic acid (20-HETE), a cytochrome CYP450-derived arachidonic acid metabolite, is known to be elevated in resistance arteries in hypertensive animal models and in obesity in humans, but the role of 20-HETE in regulation of large artery remodeling in metabolic syndrome has not been investigated. Unlike normal (Sprague-Dawley (SD)) rats, large arteries (aorta, carotid and >100μM mesenteric arteries) of metabolic syndrome rats (JCR:LA-cp, JCR) express CYP4A and 4F, CYP450s which make 20-HETE in rats (2-fold increase vs. SD). Consequently, 20-HETE production is elevated in large arteries of JCR rats. We hypothesized that this elevated 20-HETE increases matrix metalloproteinase 12 (MMP12, an elastase) activation leading to increased degradation of elastin, increased large artery stiffness and increased systolic blood pressure. A 3-4 fold increase in 20-HETE production in large arteries of JCR vs. SD rats correlated with increased elastin degradation (3-6 fold) and increased arterial stiffness (~75%). 20-HETE antagonists blocked elastin degradation in JCR rats concomitant with blocking MMP12 activation. Importantly, 20-HETE antagonists and MMP12 inhibition (pharmacological and MMP12-shRNA-Lnv) significantly decreased (~60% vs. untreated JCR) large artery stiffness in JCR rats. 20-HETE antagonists also decreased systolic (182±3 mmHg JCR, 145±3 mmHg JCR+20-HETE antagonists) but not diastolic (125±4 mmHg JCR, 124±4 mmHg JCR+20-HETE antagonists) blood pressure in JCR rats. Whereas diastolic pressure was fully angiotensin II (Ang II)-dependent, systolic pressure was only partially Ang II-dependent, and large artery stiffness in JCR rats was Ang II-independent. These results suggest that 20-HETE-dependent regulation of systolic blood pressure may be a unique feature of metabolic syndrome related to high CYP4A/4F expression and resultant high 20-HETE production in large conduit arterial stiffness, which is a primary determinant of systolic blood pressure. These findings may have implications for management of systolic hypertension in patients with metabolic syndrome.

Coronary collateral growth (CCG) is impaired in metabolic syndrome (MetS). microRNA-145 (miR-145-Adv) delivery to our rat model of MetS (JCR) completely restored and neutrophil depletion significantly improved CCG. We determined whether low endogenous levels of miR-145 in MetS allowed for elevated production of 20-hydroxyeicosatetraenoic acid (20-HETE), which, in turn, resulted in excessive neutrophil accumulation and endothelial dysfunction leading to impaired CCG. Rats underwent 0-9 days of repetitive ischemia (RI). RI-induced cardiac CYP4F (neutrophil-specific 20-HETE synthase) expression and 20-HETE levels were increased (4-fold) in JCR vs. normal rats. miR-145-Adv and 20-HETE antagonists abolished and neutrophil depletion (blocking antibodies) reduced (~60%) RI-induced increases in CYP4F expression and 20-HETE production in JCR rats. Impaired CCG in JCR rats (collateral-dependent blood flow using microspheres) was completely restored by 20-HETE antagonists [collateral-dependent zone (CZ)/normal zone (NZ) flow ratio was 0.76 ± 0.07 in JCR + 20-SOLA, 0.84 ± 0.05 in JCR + 20-HEDGE vs. 0.11 ± 0.02 in JCR vs. 0.84 ± 0.03 in normal rats]. In JCR rats, elevated 20-HETE was associated with excessive expression of endothelial adhesion molecules and neutrophil infiltration, which were reversed by miR-145-Adv. Endothelium-dependent vasodilation of coronary arteries, endothelial nitric oxide synthase (eNOS) Ser1179 phosphorylation, eNOS-dependent NO·- production and endothelial cell survival were compromised in JCR rats. These parameters of endothelial dysfunction were completely reversed by 20-HETE antagonism or miR-145-Adv delivery, whereas neutrophil depletion resulted in partial reversal (~70%). We conclude that low miR-145 in MetS allows for increased 20-HETE, mainly from neutrophils, which compromises endothelial cell survival and function leading to impaired CCG. 20-HETE antagonists could provide viable therapy for restoration of CCG in MetS.NEW & NOTEWORTHY Elevated 20-hydroxyeicosatetraenoic acid (20-HETE) impairs coronary collateral growth (CCG) in metabolic syndrome by eliciting endothelial dysfunction and apoptosis via excessive neutrophil infiltration. 20-HETE antagonists completely restore coronary collateral growth in metabolic syndrome. microRNA-145 (miR-145) is an upstream regulator of 20-HETE production in metabolic syndrome; low expression of miR-145 in metabolic syndrome promotes elevated production of 20-HETE.

Transient, repetitive myocardial ischemia (RI)-induced coronary collateral growth (CCG) is impaired in metabolic syndrome patients and animal models. Endothelial cell (EC) dysfunction and chronic inflammation are hallmarks of metabolic syndrome. We showed that while in normal animals (SD), RI induces transient infiltration of monocytes, associated with successful CCG, in metabolic syndrome rats (JCR), RI induces sustained accumulation of neutrophils, which contributes to compromised CCG. 20-hydroxyeicosatetraeonic acid (20-HETE) is a pro-inflammatory metabolite of arachidonic acid. Its role in the regulation of CCG is unknown. We hypothesized that enhanced 20-HETE-mediated neutrophil adhesion to ECs and consequent EC dysfunction and apoptosis result in impaired CCG in metabolic syndrome. P-selectin and ICAM-1 expression was increased ~40% in JCR vs. SD rats. This increase was prevented by 20-HETE antagonists, 20-SOLA or 20-HEDGE. 20-HETE antagonists also prevented neutrophil accumulation observed in JCR rats. Coronary arteries from JCR rats exhibited reduced endothelium (Ach)-dependent vasodilation (20% JCR vs. 50% of max. SD). RI-induced eNOS activation and NO production were likewise decreased (~60% and~70%, respectively) in JCR vs. SD rats. EC apoptosis (TUNEL) was severely increased in response to RI in JCR rats (~75% vs. SD). Neutrophil adhesion-blocking antibodies partially attenuated EC apoptosis (~70%) and EC dysfunction (~75% eNOS activation and NO production, 75% Ach-dependent vasodilation). 20-HETE antagonists fully reversed impaired endothelium-dependent vasodilation, eNOS activation, NO production and prevented EC apoptosis. Finally, impaired CCG in JCR rats (collateral-dependent blood flow, microspheres) was completely restored by 20-HETE antagonists (CZ/NZ flow was 0.76±0.07 in JCR+20-SOLA, 0.84±0.05 in JCR+20-HEDGE vs. 0.11±0.02 in JCR vs. 0.84±0.03 ml/min/g in SD rats) and partially restored by neutrophil-blocking antibodies (0.49±0.05 ml/min/g). Taken together, these results indicate that 20-HETE-dependent neutrophil adhesion and accumulation compromises EC survival and function leading to impaired CCG. 20-HETE antagonists could provide therapy for restoration of CCG in metabolic syndrome.

20-Hydroxyeicosatetraenoic acid (20-HETE) is a potent vasoactive eicosanoid of the microcirculation exhibiting effects on vascular smooth muscle (VSM) function that include stimulation of contractility, migration and growth. We have previously demonstrated in mice which globally overexpress 20-HETE that hypertension as well as vascular remodeling is not fully prevented by pharmacological normalization of blood pressure. However, both hypertension and vascular remodeling are prevented by antagonism of 20-HETE, suggesting that 20-HETE exerts vascular effects independent of hypertension. To examine the contribution of VSM-derived 20-HETE to hypertension and vascular remodeling, we have developed a transgenic mouse model that overexpresses the primary mouse 20-HETE synthase, Cyp4a12, specifically in VSM by crossbreeding floxed Cyp4a12 with Myh11-Cre mice. All mice carry the floxed Cyp4a12 gene and express a GFP protein under control of a modified CMV promoter. Cre-recombination excises the GFP cDNA and inserts the Cyp4a12 cDNA. Three to four month old male Cyp4a12-floxed mice carrying the Myh11-Cre gene (Cyp4a12 fl/fl Myh11 Cre+/- ) exhibited higher systolic blood pressure than control mice Cyp4a12 fl/fl Myh11 Cr-/- (WT) mice (135 vs. 115 mmHg, n=4, *p<0.05). 20-HETE production in Cyp4a12 fl/fl Myh11 Cre+/- mice were higher than in WT in mesenteric (3333±891 vs. 545± 196 ng/mg/h) and renal interlobar arteries (RIA; 1859±376 vs. 242±62 ng/mg/h). Plasma levels of 20-HETE were also elevated (324±61 vs. 185±34 pg/mL) while urinary levels were not significantly different (146±26 vs. 117±29 pg/mL). We also observed increased medial thickness and decreased lumen area of blood vessels by Myh11 immunofluorescence in heart and kidney sections. RIA from male Myh11-Cyp4a12 mice displayed higher constrictor sensitivity to phenylephrine and impaired relaxation to acetylcholine compared to WT. Taken together, these data suggest that this model displays hypertension and pathological hypertrophic vascular remodeling. We therefore conclude that the Cyp4a12 fl/fl Myh11 Cre/- is a promising and unique transgenic mouse model to examine the contribution of smooth muscle-derived 20-HETE to hypertension and hypertrophic vascular remodeling.

Obesity and its metabolic complications have emerged as the epidemic of the new millennia. The use of obese rodent models continues to be a productive component of efforts to understand the concomitant metabolic complications of this disease. In 1978, the JCR:LA-cp rat model was developed with an autosomal recessive corpulent (cp) trait resulting from a premature stop codon in the extracellular domain of the leptin receptor. Rats that are heterozygous for the cp trait are lean-prone, while those that are homozygous (cp/cp) spontaneously display the pathophysiology of obesity as well as a metabolic syndrome (MetS)-like phenotype. Over the years, there have been formidable scientific contributions that have originated from this rat model, much of which has been reviewed extensively up to 2008. The premise of these earlier studies focused on characterizing the pathophysiology of MetS-like phenotype that was spontaneously apparent in this model. The purpose of this review is to highlight areas of recent advancement made possible by this model including; emerging appreciation of the "thrifty gene" hypothesis in the context of obesity, the concept of how chronic inflammation may drive obesogenesis, the impact of acute forms of inflammation to the brain and periphery during chronic obesity, the role of dysfunctional insulin metabolism on lipid metabolism and vascular damage, and the mechanistic basis for altered vascular function as well as novel parallels between the human condition and the female JCR:LA-cp rat as a model for polycystic ovary disease (PCOS).

20-Hydroxyeicosatetraenoic acid (20-HETE) is a cytochrome P450 (CYP)-derived arachidonic acid metabolite linked to regulation of blood pressure via actions on the renal microvasculature and tubules. In renal microvessels, 20-HETE promotes vasoconstriction, vascular remodeling, and vascular injury; all of which contribute to hypertension, whereas in tubular structures 20-HETE has been linked to inhibition of sodium transport and lowering of blood pressure. Induction or global overexpression of Cyp4a12-20-HETE synthase, the primary 20-HETE producing enzyme in mice, results in hypertension. Since these mice display global overproduction of 20-HETE, it is difficult to dissect the exact contribution of vascular versus tubular 20-HETE to the hypertension. To begin addressing this issue, the current study was undertaken to define the blood pressure phenotype of novel transgenic mice with proximal tubule-specific overexpression of the Cyp4a12-20-HETE synthase (PEPCK-cyp4a12 mice). These mice generated by crossing the Cyp4a12 fl/fl with PEPCK (phosphoenolpyruvate carboxykinase promoter)-Cre mice, showed increased Cyp4a12 mRNA expression (2.6±0.9 fold increase; p<0.05) and 20-HETE production in the renal cortex (138±32 pg/mg vs. 80±6 pg/mg). Most importantly, the systolic blood pressure was markedly elevated in the PEPCK-Cyp4a12 mice as compared to WT littermates (142±2 vs. 111±3 mmHg; p<0.05). Interestingly, the PEPCK-Cyp4a12 mice exhibited significantly higher levels of urinary 20-HETE as compared to WT littermates (205±50 vs 83±5 pg/ml; p<0.05) whereas plasma 20-HETE levels remained unchanged (231±32 vs 190±25 pg/ml). Moreover, in PEPCK-Cyp4a12 (n=4) urinary volume was lower (2.15±0.05 vs 3.17±0.20 ml/day, p=0.003) and UNaV appeared lower (181±7 vs 194±25 μmol/day, p=0.35) as compared to WT littermates. These results are in line with the possibility that 20-HETE overproduction at the level of the proximal tubule promotes rather than opposes hypertension. The exact mechanisms need to be further examined.

Transient, repetitive myocardial ischemia (RI)-induced coronary collateral growth (CCG) is impaired in metabolic syndrome patients and animal models. Endothelial cell (EC) dysfunction and chronic inflammation are hallmarks of metabolic syndrome. We showed that while in normal animals (SD), RI induces transient infiltration of monocytes, associated with successful CCG, in metabolic syndrome rats (JCR), RI induces sustained accumulation of neutrophils, which contributes to compromised CCG. 20-hydroxyeicosatetraeonic acid (20-HETE) is a pro-inflammatory metabolite of arachidonic acid. Its role in the regulation of CCG is unknown. We hypothesized that enhanced 20-HETE-mediated neutrophil adhesion to ECs and consequent EC dysfunction and apoptosis result in impaired CCG in metabolic syndrome. P-selectin and ICAM-1 expression was increased ~40% in JCR vs. SD rats. This increase was prevented by 20-HETE antagonists, 20-SOLA or 20-HEDGE. 20-HETE antagonists also prevented neutrophil accumulation observed in JCR rats. Coronary arteries from JCR rats exhibited reduced endothelium (Ach)-dependent vasodilation (20% JCR vs. 50% of max. SD). RI-induced eNOS activation and NO production were likewise decreased (~60% and~70%, respectively) in JCR vs. SD rats. EC apoptosis (TUNEL) was severely increased in response to RI in JCR rats (~75% vs. SD). Neutrophil adhesion-blocking antibodies partially attenuated EC apoptosis (~70%) and EC dysfunction (~75% eNOS activation and NO production, 75% Ach-dependent vasodilation). 20-HETE antagonists fully reversed impaired endothelium-dependent vasodilation, eNOS activation, NO production and prevented EC apoptosis. Finally, impaired CCG in JCR rats (collateral-dependent blood flow, microspheres) was completely restored by 20-HETE antagonists (CZ/NZ flow was 0.76±0.07 in JCR+20-SOLA, 0.84±0.05 in JCR+20-HEDGE vs. 0.11±0.02 in JCR vs. 0.84±0.03 ml/min/g in SD rats) and partially restored by neutrophil-blocking antibodies (0.49±0.05 ml/min/g). Taken together, these results indicate that 20-HETE-dependent neutrophil adhesion and accumulation compromises EC survival and function leading to impaired CCG. 20-HETE antagonists could provide therapy for restoration of CCG in metabolic syndrome.

Coronary collateral growth (CCG) is impaired in metabolic syndrome. microRNA-21 (miR-21) is a proproliferative and antiapoptotic miR, which we showed to be elevated in metabolic syndrome. Here we investigate whether impaired CCG in metabolic syndrome involved miR-21-mediated aberrant apoptosis. Normal Sprague-Dawley (SD) and metabolic syndrome [J. C. Russel (JCR)] rats underwent transient, repetitive coronary artery occlusion [repetitive ischemia (RI)]. Antiapoptotic Bcl-2, phospho-Bad, and Bcl-2/Bax dimers were increased on days 6 and 9 RI, and proapoptotic Bax and Bax/Bax dimers and cytochrome-c release concurrently decreased in JCR versus SD rats. Active caspases were decreased in JCR versus SD rats (~50%). Neutrophils increased transiently on day 3 RI in the collateral-dependent zone of SD rats but remained elevated in JCR rats, paralleling miR-21 expression. miR-21 downregulation by anti-miR-21 induced neutrophil apoptosis and decreased Bcl-2 and Bcl-2/Bax dimers (~75%) while increasing Bax/Bax dimers, cytochrome-c release, and caspase activation (~70, 400, and 400%). Anti-miR-21 also improved CCG in JCR rats (~60%). Preventing neutrophil infiltration with blocking antibodies resulted in equivalent CCG recovery, confirming a major role for deregulated neutrophil apoptosis in CCG impairment. Neutrophil and miR-21-dependent CCG inhibition was in significant part mediated by increased oxidative stress. We conclude that neutrophil apoptosis is integral to normal CCG and that inappropriate prolonged miR-21-mediated survival of neutrophils plays a major role in impaired CCG, in part via oxidative stress generation.

Inadequate cell proliferation is considered a major causative factor for impaired coronary collateral growth (CCG). Proangiogenic growth factors (GFs) stimulate cell proliferation, but their administration does not promote CCG in patients. These GFs are increased in patients with metabolic syndrome and in animal models, where CCG is impaired. Here, we investigated whether excessive cell proliferation underlies impaired CCG in metabolic syndrome. Normal [Sprague‐Dawley (SD)] and metabolic syndrome [James C. Russell (JCR)] rats underwent repetitive ischemia (RI; transient, repetitive coronary artery occlusion and myocardial ischemia). We have shown that CCG was maximal at d 9 of RI in SD rats but did not occur in JCR rats. The increase in cell proliferation (PCNA, Ki‐67, cyclin A, phospho‐ cdc2, p21Waf, p27Kip) was transient (~4‐fold, d 3 RI) in SD rats but greater and sustained in JCR rats (~8‐ to 6‐fold, d 3‐9 RI). In JCR rats, this was associated with increased and sustained miR‐21 expression and accumulation of proliferating synthetic vascular smooth muscle cells in the lumen of small arterioles, which failed to undergo outward expansion. Administration of anti‐miR‐21 blocked RI‐induced cell proliferation and significantly improved CCG in JCR rats (~60%). miR‐21‐dependent excessive cell proliferation in the later stages of collateral remodeling correlates with impaired CCG in metabolic syndrome.—Hutcheson, R., Chaplin, J., Hutcheson, B., Borthwick, F., Proctor, S., Gebb, S., Jadhav, R., Smith, E., Russell, J. C., Rocic, P. miR‐21 normalizes vascular smooth muscle proliferation and improves coronary collateral growth in metabolic syndrome. FASEB J. 28, 4088‐4099 (2014). www.fasebj.org

RationaleCoronary collateral growth (CCG) is impaired in the metabolic syndrome. It is thought that inadequate cell proliferation is a causative factor. Pro‐angiogenic growth factors (GFs) stimulate cell proliferation. Metabolic syndrome patients and animal models exhibit elevated GF levels, but administration of GFs does not promote CCG in the metabolic syndrome.ObjectiveTo determine whether temporally inappropriate excessive cell proliferation underlies impaired CCG in the metabolic syndrome.Methods and ResultsNormal (SD) and metabolic syndrome (JCR) rats underwent transient, repetitive coronary artery occlusion (RI). We have previously shown that CCG was maximal at day 9 of RI in SD rats but did not occur in JCR rats. Cell proliferation was evaluated by immunohistochemistry (PCNA, Ki‐67) and Western blotting (PCNA). The increase in cell proliferation was transient in SD but greater and sustained in JCR rats. Assessment of cell cycle progression confirmed early and transient cell proliferation in SD vs. sustained proliferation in JCR rats. This was associated with accumulation of proliferating cells in the lumen of small arterioles in JCR rats, which failed to undergo outward expansion.ConclusionsExcessive cell proliferation in the later stages of collateral remodeling underlies impaired CCG in the metabolic syndrome. R01 HL093052

Objective— Transient, repetitive occlusion stimulates coronary collateral growth (CCG) in normal animals. Vascular smooth muscle cells (VSMCs) switch to synthetic phenotype early in CCG, then return to contractile phenotype. CCG is impaired in the metabolic syndrome. We determined whether impaired CCG was attributable to aberrant VSMC phenotypic modulation by miR-145–mediated mechanisms, and whether restoration of physiological miR-145 levels in metabolic syndrome (JCR rat) improved CCG. Approach and Results— CCG was stimulated by transient, repetitive left anterior descending artery occlusion and evaluated after 9 days by coronary blood flow measurements (microspheres). miR-145 was delivered to JCR VSMCs via adenoviral vector (miR-145-Adv). In JCR rats, miR-145 was decreased late in CCG (≈2-fold day 6; ≈4-fold day 9 versus SD), which correlated with decreased expression of smooth muscle-specific contractile proteins (≈5-fold day 6; ≈10-fold day 9 versus SD), indicative of VSMCs’ failure to return to the contractile phenotype late in CCG. miR-145 expression in JCR rats (miR-145-Adv) on days 6 to 9 of CCG completely restored VSMCs contractile phenotype and CCG (collateral/normal zone flow ratio was 0.93±0.09 JCR+miR-145-Adv versus 0.12±0.02 JCR versus 0.87±0.02 SD). Conclusions— Restoration of VSMC contractile phenotype through miR-145 delivery is a highly promising intervention for restoration of CCG in the metabolic syndrome.

Objective—We have previously shown that transient coronary artery occlusion stimulated coronary collateral growth (CCG) in healthy (Sprague Dawley) but not in metabolic syndrome (JCR:LA-cp [JCR] ) rats. Here, we sought to determine whether matrix metalloproteinases (MMPs) negatively regulate CCG in the metabolic syndrome via release of endostatin and angiostatin. Approach and Results—Rats underwent transient, repetitive left anterior descending occlusion and resultant myocardial ischemia (RI) for 0 to 10 days. CCG was measured in the collateral-dependent and normal zones using microspheres, MMP activation by Western blot, and endostatin and angiostatin by ELISA on days 0, 3, 6, 9, or 10 of RI. Endostatin and angiostatin were increased in JCR but not in Sprague Dawley rats on days 6 and 9 of RI. Increased endostatin and angiostatin correlated with increased MMP12 (≈4-fold) activation in JCR but not in Sprague Dawley rats on days 6 and 9 of RI. Inhibition of MMP12 in JCR rats nearly completely blocked endostatin (≈85%) and angiostatin (≈90%) generation and significantly improved CCG (collateral-dependent zone flow was ≈66% of normal zone flow versus ≈12% for JCR RI). Conclusions—Compromised CCG in the metabolic syndrome is, in large part, because of increased MMP12 activation and consequent increased generation of endostatin and angiostatin, which inhibits late-stage collateral remodeling.

The metabolic syndrome affects 30% of the US population with increasing prevalence. In this paper, we explore the relationship between the metabolic syndrome and the incidence and severity of cardiovascular disease in general and coronary artery disease (CAD) in particular. Furthermore, we look at the impact of metabolic syndrome on outcomes of coronary revascularization therapies including CABG, PTCA, and coronary collateral development. We also examine the association between the metabolic syndrome and its individual component pathologies and oxidative stress. Related, we explore the interaction between the main external sources of oxidative stress, cigarette smoke and air pollution, and metabolic syndrome and the effect of this interaction on CAD. We discuss the apparent lack of positive effect of antioxidants on cardiovascular outcomes in large clinical trials with emphasis on some of the limitations of these trials. Finally, we present evidence for successful use of antioxidant properties of pharmacological agents, including metformin, statins, angiotensin II type I receptor blockers (ARBs), and angiotensin II converting enzyme (ACE) inhibitors, for prevention and treatment of the cardiovascular complications of the metabolic syndrome.

In response to transient, repetitive coronary artery occlusion, small arterioles enlarge into conduit arteries by coronary collateral growth (CCG). In the early stages of CCG, vascular smooth muscl...