Xiang Wang

Tumor Necrosis Factor-α–Converting Enzyme Is a Key Regulator of Agonist-Induced Cardiac Hypertrophy and Fibrosis

Cardiac remodeling is associated with hypertrophy and fibrosis processes, which may depend on the activity of matrix metalloproteinases (MMPs) and “a disintegrin and metalloproteinases” (ADAMs). We investigated whether ADAM-17 (tumor necrosis factor-α–converting enzyme [TACE]) plays a role in agonist-induced cardiac remodeling and the relationships established among TACE, MMP-2, and ADAM-12. We targeted TACE in rodent models of spontaneous and agonist-induced hypertension using RNA interference combined with quantitative RT-PCR, activity determinations, and functional studies. Treatment of spontaneously hypertensive rats with previously validated TACE small-interfering RNA for 28 days resulted in systemic knockdown of TACE expression. TACE knockdown effectively stopped the development of cardiac hypertrophy. Mice receiving angiotensin II (1.4 mg/kg per day for 12 days) exhibited cardiac hypertrophy, as well as fibrosis, which was associated with elevated myocardial expression of molecular markers of hypertrophy (α-skeletal actin, β-myosin heavy chain, and brain natriuretic peptide) and fibrosis (collagen types I and III and fibronectin), as well as MMP-2 and ADAM-12. Treatment with TACE small-interfering RNA (but not with PBS or luciferase small-interfering RNA) inhibited TACE expression, thus preventing angiotensin II–induced cardiac hypertrophy and fibrosis. Moreover, knockdown of TACE inhibited angiotensin II–induced overexpression of markers of myocardial hypertrophy and fibrosis, as well as ADAM-12 and MMP-2. These findings provide the first in vivo evidence that agonist-induced cardiac hypertrophy and fibrosis processes are signaled through TACE, which acts through novel pathways involving transcriptional regulation of ADAM-12 and MMP-2. Targeting TACE has potential therapeutic importance for modulating agonist-induced cardiac remodeling.

MMP-2 Mediates Angiotensin II–Induced Hypertension Under the Transcriptional Control of MMP-7 and TACE

Development of cardiovascular disease induced by excessive Gq protein–coupled receptor agonist stimulation depends on signaling networks involving multiple matrix metalloproteinases (MMPs) and metalloproteinase disintegrins (ADAMs). Here, we hypothesized that MMP-2, being a major gelatinase in cardiac and vascular tissue, was likely to play a key role in cardiovascular homeostasis. We targeted MMP-2 using complementary and overlapping approaches involving pharmacological inhibition and RNA interference in mice treated with angiotensin II (1.4 mg/kg per day) for 12 days. We studied the development of hypertension (by tail cuff plethysmography), cardiac hypertrophy (by M-mode echocardiography, cardiomyocyte cross-sectional area, and quantitative real-time polymerase chain reaction (qRT-PCR) analysis of hypertrophy marker genes), and fibrosis (by picrosirius red collagen staining and qRT-PCR analysis of fibrosis marker genes) in mice receiving angiotensin II. We found that angiotensin II infusion upregulated MMP-2 concurrent with the development of hypertension, hypertrophy, and fibrosis. This upregulation of MMP-2 depended on MMP-7 and TACE (tumor necrosis factor-&agr; convertase, ADAM-17). RNA interference targeting MMP-7 and TACE attenuated the angiotensin II–induced upregulation of MMP-2 and prevented the development of hypertension, as well as development of cardiac hypertrophy and fibrosis. In contrast, pharmacological inhibition and RNA interference of MMP-2 attenuated angiotensin II–induced hypertension, without influencing development of cardiac hypertrophy or fibrosis. Downstream of MMP-7 and TACE, MMP-2 mediated angiotensin II–induced hypertension, but did not mediate cardiac hypertrophy or fibrosis. This suggests a functional specialization of MMP-2 in agonist–induced cardiovascular disease development that has potential implications for the design of metalloproteinase-based therapeutic strategies.

Matrix Metalloproteinase-7 and ADAM-12 (a Disintegrin and Metalloproteinase-12) Define a Signaling Axis in Agonist-Induced Hypertension and Cardiac Hypertrophy

Background— Excessive stimulation of Gq protein–coupled receptors by cognate vasoconstrictor agonists induces a variety of cardiovascular processes, including hypertension and hypertrophy. Here, we report that matrix metalloproteinase-7 (MMP-7) and a disintegrin and metalloproteinase-12 (ADAM-12) form a novel signaling axis in these processes. Methods and Results— In functional studies, we targeted MMP-7 in rodent models of acute, long-term, and spontaneous hypertension by 3 complementary approaches: (1) Pharmacological inhibition of activity, (2) expression knockdown (by antisense oligodeoxynucleotides and RNA interference), and (3) gene knockout. We observed that induction of acute hypertension by vasoconstrictors (ie, catecholamines, angiotensin II, and the nitric oxide synthase inhibitor NG-nitro-l-arginine methyl ester) required the posttranscriptional activation of vascular MMP-7. In spontaneously hypertensive rats, knockdown of MMP-7 (by RNA interference) resulted in attenuation of hypertension and stopped development of cardiac hypertrophy. Quantitative reverse-transcription polymerase chain reaction studies in mouse models of MMP-7 knockdown (by RNA interference) and gene knockout revealed that MMP-7 controlled the transcription of ADAM-12, the major metalloproteinase implicated in cardiac hypertrophy. In mice with angiotensin II–induced hypertension and cardiac hypertrophy, myocardial ADAM-12 and downstream hypertrophy marker genes were overexpressed. Knockdown of MMP-7 attenuated hypertension, inhibited ADAM-12 overexpression, and prevented cardiac hypertrophy. Conclusions— Agonist signaling of both hypertension and hypertrophy depends on posttranscriptional and transcriptional mechanisms that involve MMP-7, which is transcriptionally connected with ADAM-12. Approaches targeting this novel MMP-7/ADAM-12 signaling axis could have generic therapeutic potential in hypertensive disorders caused by multiple or unknown agonists.

Maintenance of adrenergic vascular tone by MMP-transactivation of the EGFR requires PI3K and mitochondrial ATP synthesis

AIMS G-protein-coupled receptors (GPCRs) modulate vascular tone, at least in part, via matrix metalloproteinase (MMP) transactivation of the epidermal growth factor receptor (EGFR). We previously have identified novel signalling pathways downstream of the EGFR suggestive of mitogen-activated protein kinase and mitochondrial redox control of vascular tone. In the present study, we examined whether MMP modulation of vascular tone involves phosphoinositide 3-kinase (PI3K) and mitochondrial ATP synthesis. METHODS AND RESULTS To determine whether PI3K is required for the maintenance of adrenergic vascular tone, we first constricted rat small mesenteric arteries with phenylephrine (PE) and then perfused with PI3K inhibitors, LY294002 and wortmannin, both of which produced a dose-dependent vasodilatation. Next, to investigate whether MMPs modulate PI3K activity, we cultured rat aortic vascular smooth muscle cells (VSMCs) and stimulated them with GPCR agonists such as PE and angiotensin II. Inhibition of MMPs (by GM6001) or EGFR (by AG1478) or suppressing the expression of MMP-2 or MMP-7 or the EGFR by small interfering RNA blunted the PI3K phosphorylation of Akt induced by PE. Further, in VSMCs, PI3K inhibitors reduced the PE-induced increase in ATP synthesis and glucose transporter-4 translocation, an effect that was also observed with MMP and the EGFR inhibitors. Further, the PE-induced increase in ATP synthesis activated MMP-7 by mechanisms involving purinergic (P2X) receptors and calcium. CONCLUSION These data suggest that the maintenance of adrenergic vascular tone by the MMP-EGFR pathway requires PI3K activation and ATP synthesis. Further, our data support the view that elevated levels of GPCR agonists exaggerate the MMP transactivation of EGFR response and contribute to enhanced vascular tone and development of cardiovascular disease such as hypertension.

Insights into the Activity, Differential Expression, Mutual Regulation, and Functions of Matrix Metalloproteinases and A Disintegrin and Metalloproteinases in Hypertension and Cardiac Disease

Hypertensive cardiac disease is a major cause of death worldwide. Causative factors of hypertension include environmental stressors, genetic predisposition, and common morbidities of lipid metabolism such as obesity and diabetes. These factors pathologically elevate the systemic production of vasoconstrictive G-protein-coupled receptor agonists. Pathological concentrations of these agonists upregulate the gene expression and proteolytic activity of matrix metalloproteinases (MMPs) and A disintegrin and metalloproteinases (ADAMs). Among the metalloproteinases that act in concert with other mediators to elevate the systemic blood pressure and to modulate the development of cardiovascular hypertrophy and fibrosis processes are MMP-2, MMP-7, ADAM-12, and ADAM-17. This review offers insights into the activity, differential expression, mutual regulation, and functions of these metalloproteinases. We further review evidence linking them to transcription factors, carrier proteins, and receptors for lipids. The emerging links between metalloproteinases and lipids are intriguing and suggest new therapeutic targets in hypertensive cardiac disease.

Matrix Metalloproteinase‐2 Negatively Regulates Cardiac Secreted Phospholipase A2 to Modulate Inflammation and Fever

Background Matrix metalloproteinase (MMP)‐2 deficiency makes humans and mice susceptible to inflammation. Here, we reveal an MMP‐2–mediated mechanism that modulates the inflammatory response via secretory phospholipase A2 (sPLA2), a phospholipid hydrolase that releases fatty acids, including precursors of eicosanoids. Methods and Results Mmp2−/− (and, to a lesser extent, Mmp7−/− and Mmp9−/−) mice had between 10‐ and 1000‐fold elevated sPLA2 activity in plasma and heart, increased eicosanoids and inflammatory markers (both in the liver and heart), and exacerbated lipopolysaccharide‐induced fever, all of which were blunted by adenovirus‐mediated MMP‐2 overexpression and varespladib (pharmacological sPLA2 inhibitor). Moreover, Mmp2 deficiency caused sPLA2‐mediated dysregulation of cardiac lipid metabolic gene expression. Compared with liver, kidney, and skeletal muscle, the heart was the single major source of the Ca2+‐dependent, ≈20‐kDa, varespladib‐inhibitable sPLA2 that circulates when MMP‐2 is deficient. PLA2G5, which is a major cardiac sPLA2 isoform, was proinflammatory when Mmp2 was deficient. Treatment of wild‐type (Mmp2+/+) mice with doxycycline (to inhibit MMP‐2) recapitulated the Mmp2−/− phenotype of increased cardiac sPLA2 activity, prostaglandin E2 levels, and inflammatory gene expression. Treatment with either indomethacin (to inhibit cyclooxygenase‐dependent eicosanoid production) or varespladib (which inhibited eicosanoid production) triggered acute hypertension in Mmp2−/− mice, revealing their reliance on eicosanoids for blood pressure homeostasis. Conclusions A heart‐centric MMP‐2/sPLA2 axis may modulate blood pressure homeostasis, inflammatory and metabolic gene expression, and the severity of fever. This discovery helps researchers to understand the cardiovascular and systemic effects of MMP‐2 inhibitors and suggests a disease mechanism for human MMP‐2 gene deficiency.

Matrix Metalloproteinase-2 Mediates a Mechanism of Metabolic Cardioprotection Consisting of Negative Regulation of the Sterol Regulatory Element–Binding Protein-2/3-Hydroxy-3-Methylglutaryl-CoA Reductase Pathway in the Heart

Previously, we reported that cardiac matrix metalloproteinase (MMP)-2 is upregulated in hypertensive mice. How MMP-2 affects the development of cardiac disease is unclear. Here, we report that MMP-2 protects from hypertensive cardiac disease. In mice infused with angiotensin II, the lack of MMP-2 (Mmp2−/−) did not affect the severity of the hypertension but caused cardiac hypertrophy to develop earlier and to a greater extent versus wild-type (Mmp2+/+) mice, as measured by heart weight:body weight ratio and upregulation of hypertrophy and fibrosis markers. We further found numerous metabolic and inflammatory gene expression abnormalities in the left ventricle of Mmp2−/− mice. Interestingly, Mmp2−/− mice expressed greater amounts of sterol regulatory element–binding protein-2 and 3-hydroxy-3-methylglutaryl-coenzyme A reductase (a target of sterol regulatory element–binding protein-2–mediated transcription and rate limiting enzyme in cholesterol and isoprenoids biosynthesis) in addition to markers of inflammation including chemokines of the C-C motif ligand family. We focused on the functionally related genes for sterol regulatory binding protein-2 and 3-hydroxy-3-methylglutaryl-coenzyme A reductase. The 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor, lovastatin, attenuated angiotensin II–induced cardiac hypertrophy and fibrosis in Mmp2−/− and wild-type (Mmp2+/+) mice, with Mmp2−/− mice showing resistance to cardioprotection by lovastatin. MMP-2 deficiency predisposes to cardiac dysfunction as well as metabolic and inflammatory gene expression dysregulation. This complex phenotype is, at least in part, because of the cardiac sterol regulatory element–binding protein-2/3-hydroxy-3-methylglutaryl-coenzyme A reductase pathway being upregulated in MMP-2 deficiency.

MMP-2 inhibits PCSK9-induced degradation of the LDL receptor in Hepa1-c1c7 cells

Low‐density lipoprotein receptor (LDLR) catalyzes the uptake of LDL‐cholesterol by liver and peripheral organs. The function of the LDLR is antagonized by pro‐protein convertase subtilisin/kexin type 9 (PCSK9), which binds to LDLR at the plasma membrane inducing LDLR degradation. Here, we report that matrix metalloproteinase‐2 (MMP‐2) interacts with and cleaves PCSK9, as evidenced by proteomic, chemical cross‐linkage, blue native‐PAGE and domain‐specific antibodies Western blot analyses. Furthermore, MMP‐2 overexpression renders Hepa1‐c1c7 cells resistant to PCSK9‐induced LDLR degradation. The data suggest that pathological MMP‐2 overexpression may protect the LDLR from PCSK‐9‐induced degradation.