Adrenoceptor blockade alters plasma gelatinase activity in patients with heart failure and MMP-9 promoter activity in a human cell line (ECV304)

Platelets and Matrix Metalloproteinases: A Bidirectional Interaction with Multiple Pathophysiologic Implications

Platelets contain and release several matrix metalloproteinases (MMPs), a highly conserved protein family with multiple functions in organism defense and repair. Platelet-released MMPs as well as MMPs generated by other cells within the cardiovascular system modulate platelet function in health and disease. In particular, a normal hemostatic platelet response to vessel wall injury may be transformed into pathological thrombus formation by platelet-released and/or by locally generated MMPs. However, it is becoming increasingly clear that platelets play a role not only in hemostasis but also in immune response, inflammation and allergy, atherosclerosis, and cancer development, and MMPs seem to contribute importantly to this role. A deeper understanding of these mechanisms may open the way to novel therapeutic approaches to the inhibition of their pathogenic effects and lead to significant advances in the treatment of cardiovascular, inflammatory, and neoplastic disorders.

Matrix Metalloproteinases in Myocardial Infarction and Heart Failure

Cardiovascular disease is the leading cause of death, accounting for 600,000 deaths each year in the United States. In addition, heart failure accounts for 37% of health care spending. Matrix metalloproteinases (MMPs) increase after myocardial infarction (MI) and correlate with left ventricular dysfunction in heart failure patients. MMPs regulate the remodeling process by facilitating extracellular matrix turnover and inflammatory signaling. Due to the critical role MMPs play during cardiac remodeling, there is a need to better understand the pathophysiological mechanism of MMPs, including the biological function of the downstream products of MMP proteolysis. Future studies developing new therapeutic targets that inhibit specific MMP actions to limit the development of heart failure post-MI are warranted. This chapter focuses on the role of MMPs post-MI, the efficiency of MMPs as biomarkers for MI or heart failure, and the future of MMPs and their cleavage products as targets for prevention of post-MI heart failure.

Carvedilol attenuates paraquat-induced lung injury by inhibition of proinflammatory cytokines, chemokine MCP-1, NF-κB activation and oxidative stress mediators

Paraquat is a highly toxic herbicide that selectively accumulates in the lungs and causes pulmonary damage through the oxidative and inflammatory processes. Carvedilol is a nonselective beta and alpha-adrenergic blocking agent that has been shown to possess powerful antioxidant and anti-inflammatory properties. In the present study, we evaluated the protective effects and the underlying mechanisms of carvedilol on paraquat-induced lung injury in a mouse model. Mice were injected with a single dose of paraquat (20mg/kg, ip), and treated with carvedilol (10 and 20mg/kg/day, orally) for eight days. At the end of the experiment, lung tissue and blood samples were collected for histological and biochemical analysis. The results showed that carvedilol treatment improved the histopathological changes in the lung tissue of mice exposed to paraquat. Carvedilol significantly decreased the levels of malondialdehyde (MDA), carbonyl protein, myeloperoxidase (MPO), and nitric oxide (NO), while increased the levels of glutathione (GSH), superoxide dismutase (SOD), catalase and glutathione reductase compared with paraquat group. Carvedilol treatment also significantly reduced the levels of proinflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, transforming growth factor (TGF)-β1 and monocyte chemoattractant protein (MCP)-1 in the lung tissue. Treatment of mice with carvedilol decreased paraquat-induced expression of nuclear factor kappa B (NF-κB). In addition the plasma levels of matrix metalloproteinase (MMP)-9 and the lung hydroxyproline content significantly reduced by carvedilol treatment. Taken together, these results indicate that carvedilol is able to decrease the severity of paraquat-induced lung injury through inhibition of inflammation and oxidative stress.

Dysregulation of Mfn2 and Drp-1 proteins in heart failure

Therapeutic approaches for cardiac regenerative mechanisms have been explored over the past decade to target various cardiovascular diseases (CVD). Structural and functional aberrations of mitochondria have been observed in CVD. The significance of mitochondrial maturation and function in cardiomyocytes is distinguished by their attribution to embryonic stem cell differentiation into adult cardiomyocytes. An abnormal fission process has been implicated in heart failure, and treatment with mitochondrial division inhibitor 1 (Mdivi-1), a specific inhibitor of dynamin related protein-1 (Drp-1), has been shown to improve cardiac function. We recently observed that the ratio of mitofusin 2 (Mfn2; a fusion protein) and Drp-1 (a fission protein) was decreased during heart failure, suggesting increased mitophagy. Treatment with Mdivi-1 improved cardiac function by normalizing this ratio. Aberrant mitophagy and enhanced oxidative stress in the mitochondria contribute to abnormal activation of MMP-9, leading to degradation of the important gap junction protein connexin-43 (Cx-43) in the ventricular myocardium. Reduced Cx-43 levels were associated with increased fibrosis and ventricular dysfunction in heart failure. Treatment with Mdivi-1 restored MMP-9 and Cx-43 expression towards normal. In this review, we discuss mitochondrial dynamics, its relation to MMP-9 and Cx-43, and the therapeutic role of fission inhibition in heart failure.

The relationship between the MMP system, adrenoceptors and phosphoprotein phosphatases

The MMPs and their inhibitors [tissue inhibitor of MMPs (TIMPs)] form the mainstay of extracellular matrix homeostasis. They are expressed in response to numerous stimuli including cytokines and GPCR activation. This review highlights the importance of adrenoceptors and phosphoprotein phosphatases (PPP) in regulating MMPs in the cardiovascular system, which may help explain some of the beneficial effects of targeting the adrenoceptor system in tissue remodelling and will establish emerging crosstalk between these three systems. Although α- and β-adrenoceptor activation increases MMP but decreases TIMP expression, MMPs are implicated in the growth stimulatory effects of adrenoceptor activation through transactivation of epidermal growth factor receptor. Furthermore, they have recently been found to catalyse the proteolysis of β-adrenoceptors and modulate vascular tone. While the mechanisms underpinning these effects are not well defined, reversible protein phosphorylation by kinases and phosphatases may be key. In particular, PPP (Ser/Thr phosphatases) are not only critical in resensitization and internalization of adrenoceptors but also modulate MMP expression. The interrelationship is complex as isoprenaline (ISO) inhibits okadaic acid [phosphoprotein phosphatase type 1/phosphoprotein phosphatase type 2A (PP2A) inhibitor]-mediated MMP expression. While this may be simply due to its ability to transiently increase PP2A activity, there is evidence for MMP-9 that ISO prevents okadaic acid-mediated expression of MMP-9 through a β-arrestin, NF-κB-dependent pathway, which is abolished by knock-down of PP2A. It is essential that crosstalk between MMPs, adrenoceptors and PPP are investigated further as it will provide important insight into how adrenoceptors modulate cardiovascular remodelling, and may identify new targets for pharmacological manipulation of the MMP system.

Okadaic acid induces matrix metalloproteinase-9 expression in fibroblasts: crosstalk between protein phosphatase inhibition and β-adrenoceptor signalling

BACKGROUND AND PURPOSE

Interactions between protein phosphatase inhibition and matrix metalloproteinase (MMP)-9 expression have implications for tissue remodelling after injury. Stimulation of β-adrenoceptors could affect such interactions as isoprenaline increases protein phosphatase 2A (PP2A) activity and MMP-9 abundance. We investigated the effect of okadaic acid (OA) on MMP-9 expression to assess interactions between phosphatase inhibition and β-adrenoceptor signalling in fibroblasts.

EXPERIMENTAL APPROACH

Fibroblasts were exposed to OA alone and in combination with isoprenaline. Effects on MMP-9 expression and intracellular signalling were studied using promoter assays, Western blot analysis and siRNA methodologies.

KEY RESULTS

Okadaic acid increased MMP-9 abundance in human cardiac ventricular fibroblasts, NIH3T3 fibroblasts and hepatic stellate cells. This effect was unaffected by PP2A knockdown in NIH3T3 cells. OA increased phosphorylation of NF-κB, but not NF-κB promoter activity, IκBα degradation, or nuclear translocation of p65-NF-κB. Exposure to SB202190 (p38 MAPK), U0126 (ERK1/2) and NF-κB III inhibitor revealed that OA induced MMP-9 activity through p38 MAPK. Isoprenaline inhibited OA-mediated MMP-9 expression in NIH3T3, in a β-arrestin 2- and PP2A-dependent manner. Mutation of the activator protein-1 (AP-1) and NF-κB binding sites demonstrated that OA-induced MMP-9 activity was mediated through the AP-1 but not NF-κB sites. The latter mediated the inhibitory effect of isoprenaline on OA-induced MMP-9 promoter activity.

CONCLUSION AND IMPLICATIONS

Okadaic acid induced MMP-9 activity through p38 MAPK and was inhibited by isoprenaline via a pathway involving β-arrestin 2, PP2A and an NF-κB binding motif. These findings elucidate how phosphoprotein phosphatases and adrenoceptors may modulate tissue remodelling by affecting fibroblast function.

Left ventricular remodeling in the post-infarction heart: a review of cellular, molecular mechanisms, and therapeutic modalities

As more patients survive myocardial infarctions, the incidence of heart failure increases. After an infarction, the human heart undergoes a series of structural changes, which are governed by cellular and molecular mechanisms in a pathological metamorphosis termed "remodeling." This review will discuss the current developments in our understanding of these molecular and cellular events in remodeling and the various pharmacological, cellular and device therapies used to treat, and potentially retard, this condition. Specifically, this paper will examine the neurohormonal activity of the renin-angiotensin-aldosterone axis and its molecular effects on the heart. The emerging understanding of the extra-cellular matrix and the various active molecules within it, such as the matrix metalloproteinases, elicits new appreciation for their role in cardiac remodeling and as possible future therapeutic targets. Cell therapy with stem cells is another recent therapy with great potential in improving post-infarcted hearts. Lastly, the cellular and molecular effects of left ventricular assist devices on remodeling will be reviewed. Our increasing knowledge of the cellular and molecular mechanisms underlying cardiac remodeling enables us not only to better understand how our more successful therapies, like angiotensin-converting enzyme inhibitors, work, but also to explore new therapies of the future.

Early use of beta-blockers attenuates systemic inflammatory response and lung oxygenation impairment after distal type acute aortic dissection

We have reported that serum C-reactive protein (CRP) elevation is an independent predictor of lung oxygenation impairment (LOI) after distal type acute aortic dissection (AAD). Systemic activation of the inflammatory system after aortic injury may play a role in the development of LOI. The aim of this study is to clarify the effect of beta-blockers on systemic inflammation and the development of LOI after distal type AAD. A total of 49 patients, who were admitted with distal type AAD and treated conservatively, were examined. White blood cell (WBC) count, serum CRP level, and arterial blood gases were measured serially. Forty patients received beta-blocker treatment within 24 h of the onset, while 9 patients received no beta-blocker treatment. Maximum WBC count, maximum CRP level, lowest PaO₂/FiO₂ (P/F) ratio, and patient background were compared between the two groups. There was no difference between the groups according to age, sex, coronary risk factors, blood pressure, serum level of CRP, WBC count, and oxygenation index on admission. Beta-blocker treatment was associated with lower maximum WBC count (P = 0.0028) and lower maximum serum CRP level (P = 0.0004). The minimum P/F ratio was higher in patients with beta-blocker treatment than in those without (P = 0.0076). Multivariate analysis revealed that administration of a beta-blocker was an independent negative determinant of LOI (P/F ratio ≤200 mmHg). In conclusion, early use of beta-blockers prevented excessive inflammation and LOI after distal type AAD, suggesting a pleiotropic effect of beta-blockers on the inflammatory response after AAD.

Long-term doxycycline is more effective than atenolol to prevent thoracic aortic aneurysm in marfan syndrome through the inhibition of matrix metalloproteinase-2 and -9

Beta-blockers, eg, atenolol, are the cornerstone therapy for thoracic aortic aneurysm (TAA) in patients with Marfan syndrome; however, continued aortic dilatation has been reported. We have demonstrated that matrix metalloproteinase (MMP)-2 and -9 were upregulated during progression of TAA in Marfan syndrome, accompanied with degenerated elastic fibers and vasomotor dysfunction. We hypothesized that doxycycline, a nonspecific inhibitor of MMPs, would ameliorate TAA by attenuating elastic fiber degeneration and improving vasomotor function. A well-characterized mouse model of Marfan syndrome (Fbn1(C1039G/+)) was used. Mice were untreated (n=40), given doxycycline (0.24 g/L, n=30), or given atenolol (0.5 g/L, n=30) in drinking water at 6 weeks of age. The Fbn1(+/+) mice served as control (n=40). At 3, 6, and 9 months, aortic segments from the ascending, arch, and descending portions were used to obtain the "average" value of the whole thoracic aorta. TAA was prevented in the doxycycline group, whereas mild aneurysm was evident in the atenolol group. Doxycycline improved elastic fiber integrity, normalized aortic stiffness, and prevented vessel weakening. The impairment of vasocontraction and endothelium-dependent relaxation in the untreated and atenolol groups were improved by doxycycline. The upregulation of transforming growth factor-beta in the Marfan aorta was suppressed by doxycycline. Doxycycline augmented expression ratios of tissue inhibitors of MMP to MMPs. Intraperitoneally injected neutralizing antibodies against MMP-2 and -9 yielded similar effects to doxycycline. We concluded that long-term treatment with doxycycline, through the inhibition of MMP-2 and -9, is more effective than atenolol in preventing TAA in Marfan syndrome by preserving elastic fiber integrity, normalizing vasomotor function, and reducing transforming growth factor-beta activation.