MMP-2: is too low as bad as too high in the cardiovascular system?

Matrix metalloproteinase (MMP)-2 cleaves a broad spectrum of substrates, including extracellular matrix components (responsible for normal tissue remodeling) and cytokines (modulators of the inflammatory response to physiological insults such as tissue damage). MMP-2 expression is elevated in many cardiovascular pathologies (e.g., myocardial infarction, hypertensive heart disease) where tissue remodeling and inflammatory responses are perturbed. Thus, it has generally been assumed that blockade of MMP-2 activity will yield therapeutic effects. Here, we provide a counterargument to this dogma based on 1) preclinical studies on Mmp2-null ( Mmp2-/-) mice and 2) clinical studies on patients with inactivating MMP2 gene mutations. Furthermore, we put forward the hypothesis that, when MMP-2 activity falls below baseline, the bioavailability of proinflammatory cytokines normally cleaved and inactivated by MMP-2 increases, leading to the production of cytokines and cardiac secretion of phospholipase A2 activity into the circulation, which stimulate systemic inflammation that perturbs lipid metabolism in target organs. Finally, we suggest that insufficient understanding of the consequences of MMP-2 deficiency remains a major factor in the failure of MMP-2 inhibitor-based therapeutic approaches. This paucity of knowledge precludes our ability to effectively intervene in cardiovascular and noncardiovascular pathologies at the level of MMP-2.

Endothelial nitric oxide synthase: From biochemistry and gene structure to clinical implications of NOS3 polymorphisms.

Nitric oxide (NO) is an important vasodilator with a well-established role in cardiovascular homeostasis. While mediator is synthesized from L-arginine by neuronal, endothelial, and inducible nitric oxide synthases (NOS1,NOS3 and NOS2 respectively), NOS3 is the most important isoform for NO formation in the cardiovascular system. NOS3 is a dimeric enzyme whose expression and activity are regulated at transcriptional, posttranscriptional,and posttranslational levels. The NOS3 gene, which encodes NOS3, exhibits a number of polymorphic sites including single nucleotide polymorphisms (SNPs), variable number of tandem repeats (VNTRs), microsatellites, and insertions/deletions. Some NOS3 polymorphisms show functional effects on NOS3 expression or activity, thereby affecting NO formation. Interestingly, many studies have evaluated the effects of functional NOS3 polymorphisms on disease susceptibility and drug responses. Moreover, some studies have investigated how NOS3 haplotypes may impact endogenous NO formation and disease susceptibility. In this article,we carried out a comprehensive review to provide a basic understanding of biochemical mechanisms involved in NOS3 regulation and how genetic variations in NOS3 may translate into relevant clinical and pharmacogenetic implications.

Aldosterone's mechanism of action: roles of lysine-specific demethylase 1, caveolin and striatin.

PURPOSE OF REVIEW: Aldosterone's functions and mechanisms of action are different depending on the tissue and the environmental condition. The mineralocorticoid receptor is present in tissues beyond epithelial cells, including the heart and vessels. Furthermore, aldosterone has direct adverse effects by both genomic and rapid/nongenomic actions not only through a nuclear receptor but also through caveolae-mediated intracellular events. Also, multiple environmental-genetic interactions play an important role in salt-sensitive hypertension (SSH) and aldosterone modulation. These findings have reshaped our vision of aldosterone's role in cardiovascular pathophysiology. This review describes new mediators of aldosterone's mechanisms of action: lysine-specific demethylase 1 (LSD1), caveolin 1 (cav-1) and striatin. RECENT FINDINGS: LSD1, an epigenetic regulator, is involved in the pathogenesis of SSH in both humans and rodents. In addition, cav-1, the main component of caveolae, plays a substantial role in mediating aldosterone pathways of SSH. The mineralocorticoid receptor interacts with cav-1 and is modulated by sodium intake. Finally, striatin, a scaffolding protein, mediates a novel interaction between signalling molecules and mineralocorticoid receptor's rapid effects in the cardiovascular system. SUMMARY: Substantial progress in aldosterone's functions and mechanisms of action should facilitate the study of cardiovascular diseases and the role of sodium intake in aldosterone-induced damage.

Angiotensina-(1-9) disminuye el remodelamiento cardiovascular hipertensivo independiente de los niveles de ECA y de angiotensina II / Angiotensin-(1-) reduces hypertensive cardiovascular remodeling independent of ACE and Ang II levels

Resumen: La enzima convertidora de angiotensina I (ECA2) a través de Angiotensina (Ang)-(1-9) más que Ang-(1-7) contrarresta los efectos deletéreos de ECA y Ang II. Se desconoce si Ang-(1-9) es efectiva en el tratamiento del remodelamiento cardiovascular (RMCV) hipertensivo, en ratas con polimorfismo del gen de la ECA. Objetivo: Determinar el efecto de Ang-(1-9) en el tratamiento del RMCV hipertensivo en ratas con niveles genéticamente determinados de ECA y Ang II. Métodos: Ratas normotensas homocigotas, Lewis (LL) y Brown Norway (BN), se les indujo HTA a través del modelo Goldblatt (GB, 2 riñones-1 pinzado). Después de 4 semanas, las ratas hipertensas se rando-mizaron para recibir Ang-(1-9) (602 ng/Kg min) o una coadministración de Ang-(1-9)+A779 (100 ng/Kg min, antagonista del receptor MAS de Ang-(1-7)) durante 14 días mediante una minibomba. Como controles se usaron ratas sometidas a operación ficticia (Sham). Se determinó masa corporal (MC), presión arterial sistólica (PAS), masa ventricular (MV), área de cardiomiocitos (AC), área y grosor de la túnica media (ATM, GTM), fracción volumétrica de colágeno total (FVCT) en el ventrículo izquierdo (VI), niveles proteicos de colágeno tipo I (Col I) en la aorta (Ao) y la infiltración de macrófagos en Ao y VI, por medio de su molécula especifica ED1 (ED1-Ao, ED1-VI). Resultados: La administración de Ang-(1-9) disminuyó significativamente PAS, MV, AC, FVCT, Col I, ATM, GTM, ED1-Ao (-) y ED1-VI, en las ratas hipertensas LL y BN respecto a las ratas GB sin tratamiento, respectivamente. Este efecto no fue inhibido por el antagonista A779. El polimorfismo de la ECA no modificó la respuesta al tratamiento. Conclusión: Ang-(1-9) redujo eficazmente la HTA y el RMCV secundario, independiente al polimorfismo en el gen de la ECA. Este efecto posiblemente es directo ya que no fue mediado por Ang-(1-7). Fondecyt 1100874.

Background: The angiotensin I converting enzyme 2 (ACE2) counteracts the deleterious effects of ACE and Ang II through angiotensin (Ang) -(1-9) rather than Ang-(1-7). In addition, it is not clear whether Ang-(1-9) is effective in the reversal of hypertensive cardiovascular remodeling (CVRM) in rats with ACE gene polymorphism. Objective: To determine the effect of Ang-(1-9) in the prevention of hypertensive CVRM in rats with genetically determined levels of ACE and Ang II. Methods: In normotensive homozygous Lewis (LL) and Brown Norway (BN) rats hypertension was induced by the Goldblatt 2 kidney-1 pinch model. After 4 weeks, rats were randomized to receive Ang- (1-9) (602 ng / Kg min) or the co administration of Ang- (19) + A779 (100 ng / kg min, a MAS receptor antagonist of Ang- (1-7)) for 14 days. Sham operated rats were used as controls. We determined body mass (BM), systolic blood pressure (SBP), ventricular mass (VM), cardiomyocyte area (CA), area and thickness of the aortic media (ATM, TTM), LV total collagen volume fraction (FVCT), type I collagen protein levels (Col I) in the aorta (Ao) and macrophage infiltration in LV and Ao, through its specific molecule ED1 (ED1-Ao, ED1-VI). Results: Continuous administration of Ang- (1-9) significantly decreased SBP, VM, CA, TCVF, Col I, TTM, and ED1 in the aorta and left ventricle of hypertensive rats. This effect was not inhibited by the antagonist A779. ACE polymorphism did not modify the response to treatment. Conclusion: Ang- (1-9) effectively reduced hypertension induced CVRM independent of ACE gene polymorphism. This effect was not mediated by Ang- (1-7).

Doxycycline dose-dependently inhibits MMP-2-mediated vascular changes in 2K1C hypertension.

Hypertension induces vascular alterations that are associated with up-regulation of matrix metalloproteinases (MMPs). While these alterations may be blunted by doxycycline, a non-selective MMPs inhibitor, no previous study has examined the effects of different doses of doxycycline on these alterations. This is important because doxycycline has been used at sub-antimicrobial doses, and the use of lower doses may prevent the emergence of antibiotic-resistant microorganisms. We studied the effects of doxycycline at 3, 10 and 30 mg/kg per day on the vascular alterations found in the rat two kidney-one clip (2K1C) hypertension (n = 20 rats/group). Systolic blood pressure (SBP) was monitored during 4 weeks of treatment. We assessed endothelium-dependent and independent relaxations. Quantitative morphometry of structural changes in the aortic wall was studied, and aortic MMP-2 levels/proteolytic activity were determined by gelatin and in situ zymography, respectively. All treatments attenuated the increases in SBP in hypertensive rats (195.4 ± 3.9 versus 177.2 ± 6.2, 176.3 ± 4.5, and 173 ± 5.1 mmHg in 2K1C hypertensive rats treated with vehicle, or doxycycline at 3, 10, 30 mg/kg per day, respectively (all p < 0.01). However, only the highest dose prevented 2K1C-induced reduction in endothelium-dependent vasorelaxation (p < 0.05), vascular hypertrophy and increases in MMP-2 levels (all p < 0.05). In conclusion, our results suggest that relatively lower doses of doxycycline do not attenuate the vascular alterations found in the 2K1C hypertension model, and only the highest dose of doxycycline affects MMPs and vascular structure. Our results support the idea that the effects of doxycycline on MMP-2 and vascular structure are pressure independent.

Evidence for the involvement of matrix metalloproteinases in the cardiovascular effects produced by nicotine.

Nicotine plays a role in smoking-associated cardiovascular diseases, and may upregulate matrix metalloproteinase (MMP)-2 and MMP-9. We examined whether nicotine induces the release of MMP-2 and MMP-9 by rat smooth muscle cells (SMC), and whether doxycycline (non-selective MMP inhibitor) inhibits the vascular effects produced by nicotine. SMC were incubated with nicotine 0, 50, and 150 nM for 48 h. MMP-2 and MMP-9 levels in the cell supernatants were determined by gelatin zymography. The acute changes in mean arterial pressure caused by nicotine 2 micromol/kg (or saline) were assessed in rats pretreated with doxycycline (or saline). We also examined whether doxcycline (30 mg/Kg, i.p., daily) modifies the effects of nicotine (10mg/kg/day; 4 weeks) on the endothelium-dependent relaxations of rat aortic rings. Aortic MMP-2 levels were assessed by gelatin zymography. Aortic gelatinolytic activity was assessed using a gelatinolytic activity kit. MMP-2 and MMP-9 levels increased in the supernatant of SMC cells incubated with nicotine 150 nM (P<0.05) but not with 50 nM. Nicotine (2 micromol/kg) produced lower increases in the mean arterial pressure in rats pretreated with doxycycline than those found in rats pretreated with saline (26+/-4 vs. 37+/-4 mm Hg, respectively; P<0.05). Nicotine impaired of the endothelium-dependent responses to acetylcholine, and treatment with doxycycline increased the potency (pD2) by approximately 25% (P<0.05). While we found no significant differences in aortic MMP-2 levels, nicotine significantly increased gelatinolytic activity (P<0.05). These findings suggest that nicotine produces cardiovascular effects involving MMPs. It is possible that MMPs inhibition may counteract the effects produced by nicotine.

Angiotensin I-converting enzyme (kininase II) in cardiovascular and renal regulations and diseases.

The angiotensin I-converting enzyme (kininase II, ACE) is the major angiotensin II forming and kinin degrading enzyme in the circulation, and has other physiological peptide substrates. Recent studies have established that the interindividual variability in the levels of ACE in plasma and tissues is under the influence of a genetic polymorphism. The genetic polymorphism of ACE levels has been linked in case-control studies to the susceptibility of developing cardiovascular diseases, especially myocardial infarction and diabetic nephropathy, and to the risk of progression of renal diseases. The new concept that the level of ACE in peripheral circulations and tissue interstitium is an important factor in the determinism of the local concentration of peptides and their putative protective/deleterious effects, especially in the kidney and the heart, will be further appraised.