Therapeutic applications of chymase inhibitors in cardiovascular diseases and fibrosis

Plasma Chymase Activity Reflects the Change in Hemodynamics Observed after the Surgical Treatment of Patent Ductus Arteriosus in Dogs

Chymase is a protease stored in mast cell granules that produces angiotensin II (ANG II) from angiotensin I (ANG I) and is associated with tissue injury, inflammation, and remodeling, especially involving the cardiovascular system. As cardiovascular events occur, chymase is activated by degranulation to the extracellular matrix. Although chymase has been suggested to be associated with cardiovascular disease progression, there are not enough reports in veterinary medicine. Patent ductus arteriosus (PDA) is a common congenital cardiac disease in veterinary medicine. Almost all cases of PDA can be treated surgically to prevent the development of congestive heart disease and/or pulmonary hypertension. The aims of the present study were to measure chymase activity before and after PDA occlusions, and to investigate the relationships between the congestive and hemodynamic states of PDA and chymase activity. In the present study, 17 puppies diagnosed with PDA were included and all puppies completely recovered to the level of healthy dogs. Chymase activity significantly decreased at 2 months after the operation, along with the echocardiography parameters of congestion. Therefore, plasma chymase activity may be useful as a novel predictor for understanding the hemodynamics of PDA in veterinary medicine.

Histamine receptors in heart failure

The biogenic amine, histamine, is found predominantly in mast cells, as well as specific histaminergic neurons. Histamine exerts its many and varied actions via four G-protein-coupled receptors numbered one through four. Histamine has multiple effects on cardiac physiology, mainly via the histamine 1 and 2 receptors, which on a simplified level have opposing effects on heart rate, force of contraction, and coronary vasculature function. In heart failure, the actions of the histamine receptors are complex, the histamine 1 receptor appears to have detrimental actions predominantly in the coronary vasculature, while the histamine 2 receptor mediates adverse effects on cardiac remodeling via actions on cardiomyocytes, fibroblasts, and even endothelial cells. Conversely, there is growing evidence that the histamine 3 receptor exerts protective actions when activated. Little is known about the histamine 4 receptor in heart failure. Targeting histamine receptors as a therapeutic approach for heart failure is an important area of investigation given the over-the-counter access to many compounds targeting these receptors, and thus the relatively straight forward possibility of drug repurposing. In this review, we briefly describe histamine receptor signaling and the actions of each histamine receptor in normal cardiac physiology, before describing in more detail the known role of each histamine receptor in adverse cardiac remodeling and heart failure. This includes information from both clinical studies and experimental animal models. It is the goal of this review article to bring more focus to the possibility of targeting histamine receptors as therapy for heart failure.

Renin angiotensin aldosterone inhibition in the treatment of cardiovascular disease

A collective century of discoveries establishes the importance of the renin angiotensin aldosterone system in maintaining blood pressure, fluid volume and electrolyte homeostasis via autocrine, paracrine and endocrine signaling. While research continues to yield new functions of angiotensin II and angiotensin-(1-7), the gap between basic research and clinical application of these new findings is widening. As data accumulates on the efficacy of angiotensin converting enzyme inhibitors and angiotensin II receptor blockers as drugs of fundamental importance in the treatment of cardiovascular and renal disorders, it is becoming apparent that the achieved clinical benefits is suboptimal and surprisingly no different than what can be achieved with other therapeutic interventions. We discuss this issue and summarize new pathways and mechanisms effecting the synthesis and actions of angiotensin II. The presence of renin-independent non-canonical pathways for angiotensin II production are largely unaffected by agents inhibiting renin angiotensin system activity. Hence, new efforts should be directed to develop drugs that can effectively block the synthesis and/or action of intracellular angiotensin II. Improved drug penetration into cardiac or renal sites of disease, inhibiting chymase the primary angiotensin II forming enzyme in the human heart, and/or inhibiting angiotensinogen synthesis would all be more effective strategies to inhibit the system. Additionally, given the role of angiotensin II in the maintenance of renal homeostatic mechanisms, any new inhibitor should possess greater selectivity of targeting pathogenic angiotensin II signaling processes and thereby limit inappropriate inhibition.

Intracrine angiotensin II functions originate from noncanonical pathways in the human heart

Although it is well-known that excess renin angiotensin system (RAS) activity contributes to the pathophysiology of cardiac and vascular disease, tissue-based expression of RAS genes has given rise to the possibility that intracellularly produced angiotensin II (Ang II) may be a critical contributor to disease processes. An extended form of angiotensin I (Ang I), the dodecapeptide angiotensin-(1-12) [Ang-(1-12)], that generates Ang II directly from chymase, particularly in the human heart, reinforces the possibility that an alternative noncanonical renin independent pathway for Ang II formation may be important in explaining the mechanisms by which the hormone contributes to adverse cardiac and vascular remodeling. This review summarizes the work that has been done in evaluating the functional significance of Ang-(1-12) and how this substrate generated from angiotensinogen by a yet to be identified enzyme enhances knowledge about Ang II pathological actions.

Chymase: a multifunctional player in pulmonary hypertension associated with lung fibrosis

Limited literature sources implicate mast-cell mediator chymase in the pathologies of pulmonary hypertension and pulmonary fibrosis. However, there is no evidence on the contribution of chymase to the development of pulmonary hypertension associated with lung fibrosis, which is an important medical condition linked with increased mortality of patients who already suffer from a life-threatening interstitial lung disease.The aim of this study was to investigate the role of chymase in this particular pulmonary hypertension form, by using a bleomycin-induced pulmonary hypertension model.Chymase inhibition resulted in attenuation of pulmonary hypertension and pulmonary fibrosis, as evident from improved haemodynamics, decreased right ventricular remodelling/hypertrophy, pulmonary vascular remodelling and lung fibrosis. These beneficial effects were associated with a strong tendency of reduction in mast cell number and activity, and significantly diminished chymase expression levels. Mechanistically, chymase inhibition led to attenuation of transforming growth factor β1 and matrix-metalloproteinase-2 contents in the lungs. Furthermore, chymase inhibition prevented big endothelin-1-induced vasoconstriction of the pulmonary arteries.Therefore, chymase plays a role in the pathogenesis of pulmonary hypertension associated with pulmonary fibrosis and may represent a promising therapeutic target. In addition, this study may provide valuable insights on the contribution of chymase in the pulmonary hypertension context, in general, regardless of the pulmonary hypertension form.

Carrier interactions with the biological barriers of the lung: advanced in vitro models and challenges for pulmonary drug delivery

In recent years significant progress has been made to improve particle deposition in the lung. However, the development of strategies to overcome the air-blood lung barrier is still needed. The combination of complex in vitro models and sophisticated particulate carriers is promising as a strategy by which that goal could be achieved. In this review we discuss currently available in vitro lung models, including some recent tissue-engineering approaches, as well as the challenges associated to implement such complex in vitro systems. Furthermore, we discuss available carrier technologies, often based on nanotechnology, to target specific regions of the lungs and to overcome the respective biological barriers, ideally resulting in safe and effective delivery to the desired pulmonary destination.

Histological characterization of mast cell chymase in patients with pulmonary hypertension and chronic obstructive pulmonary disease

Our previous findings demonstrated an increase in pulmonary mast cells (MCs) in idiopathic pulmonary arterial hypertension (IPAH). Also, literature suggests a potential role for MCs in chronic obstructive pulmonary disease (COPD). However, a comprehensive investigation of lungs from patients is still needed. We systematically investigated the presence/expression of MCs/MC chymase in the lungs of IPAH and COPD patients by (immuno)histochemistry and subsequent quantification. We found that total and perivascular chymase-positive MCs were significantly higher in IPAH patients than in donors. In addition, chymase-positive MCs were located in proximity to regions with prominent expression of big-endothelin-1 in the pulmonary vessels of IPAH patients. Total and perivascular MCs around resistant vessels were augmented and a significant majority of them were degranulated (activated) in COPD patients. While the total chymase-positive MC count tended to increase in COPD patients, the perivascular number was significantly enhanced in all vessel sizes analyzed. Surprisingly, MC and chymase-positive MC numbers positively correlated with better lung function in COPD. Our findings suggest that activated MCs, possibly by releasing chymase, may contribute to pulmonary vascular remodeling in IPAH. Pulmonary MCs/chymase may have compartment-specific (vascular vs. airway) functions in COPD. Future studies should elucidate the mechanisms of MC accumulation and the role of MC chymase in pathologies of these severe lung diseases.

Synthesis and preliminary in vitro activity of mono- and bis-1H-1,2,3-triazole-tethered β-lactam-isatin conjugates against the human protozoal pathogen Trichomonas vaginalis

In this study, we describe the synthesis of mono- and bis-1H-1,2,3-triazole-tethered β-lactam-isatin conjugates using copper-catalysed azide-alkyne cycloaddition reaction between mono- and di-propargylated azetidin-2-ones and N-alkylazido isatins. The synthesized conjugates were evaluated for their preliminary in vitro analysis against Trichomonas vaginalis at 50 μM. The efficacy of synthesized hybrids was observed to depend on the substituent at N-1 position of β-lactam ring, as well as the presence of single/double 1H-1,2,3-triazole linker. Among the synthesized conjugates, the presence of a p-tolyl substituent at N-1 of β-lactam ring was preferred for good activity profiles while the increase in spacer length did not influence the efficacy of the compounds. Compounds with high levels of potency were further analysed to determine their IC50 values, as well as cytotoxicity profiles against mammalian cells. The most active compound in the synthesized conjugates displayed an IC50 value of 10.49 μM against cultured G3 strain of T. vaginalis and was non-toxic to cultured mammalian HeLa cells at the same concentration.

The possible potential therapeutic targets for drug induced gingival overgrowth

Gingival overgrowth is a side effect of certain medications. The most fibrotic drug-induced lesions develop in response to therapy with phenytoin, the least fibrotic lesions are caused by cyclosporin A, and the intermediate fibrosis occurs in nifedipine-induced gingival overgrowth. Fibrosis is one of the largest groups of diseases for which there is no therapy but is believed to occur because of a persistent tissue repair program. During connective tissue repair, activated gingival fibroblasts synthesize and remodel newly created extracellular matrix. Proteins such as transforming growth factor (TGF), endothelin-1 (ET-1), angiotensin II (Ang II), connective tissue growth factor (CCN2/CTGF), insulin-like growth factor (IGF), and platelet-derived growth factor (PDGF) appear to act in a network that contributes to the development of gingival fibrosis. Since inflammation is the prerequisite for gingival overgrowth, mast cells and its protease enzymes also play a vital role in the pathogenesis of gingival fibrosis. Drugs targeting these proteins are currently under consideration as antifibrotic treatments. This review summarizes recent observations concerning the contribution of TGF-β, CTGF, IGF, PDGF, ET-1, Ang II, and mast cell chymase and tryptase enzymes to fibroblast activation in gingival fibrosis and the potential utility of agents blocking these proteins in affecting the outcome of drug-induced gingival overgrowth.

Renin released from mast cells activated by circulating MCP-1 initiates the microvascular phase of the systemic inflammation of alveolar hypoxia

Reduced alveolar Po(2) in rats produces a rapid systemic inflammation characterized by reactive O(2) species generation, mast cell (MC) degranulation, leukocyte-endothelial interactions, and increased vascular permeability. The inflammation is not initiated by the low systemic Po(2) but rather by the release of monocyte chemoattractant protein-1 (MCP-1) from alveolar macrophages (AMO) activated by alveolar hypoxia. Circulating AMO-borne MCP-1 induces MC degranulation, which activates the local renin-angiotensin system (RAS) and mediates the microvascular inflammation. This study was directed to determine the mechanism of RAS activation by MCP-1-induced MC degranulation. Experiments in isolated rat peritoneal MCs showed the following: 1) Western blots and immunocytochemistry demonstrated the presence of renin and angiotensin-converting enzyme (ACE) in MCs and their release upon degranulation; 2) MCP-1-induced degranulation of MCs incubated in plasma produced an increase in angiotensin II (ANG II) concentration; and 3) this increase was inhibited completely by the following agents: the MCP-1 receptor antagonist RS-102895, the specific rat renin inhibitor WFML, or the ACE inhibitor captopril administered separately. Captopril also inhibited ANG II generation by MCs incubated in culture medium plus ANG I. The results show that peritoneal MCs contain active renin, which activates the RAS upon degranulation, and that peritoneal MCs are a source of ACE and suggest that conversion of ANG I to ANG II is mediated predominantly by ACE. This study provides novel evidence of the presence of active renin in rat peritoneal MCs and helps explain the mechanism of activation of the RAS during alveolar hypoxia.

Mast cell proteases as protective and inflammatory mediators

Proteases are the most abundant class of proteins produced by mast cells. Many of these are stored in membrane-enclosed intracellular granules until liberated by degranulating stimuli, which include cross-linking of high affinity IgE receptor F(c)εRI by IgE bound to multivalent allergen. Understanding and separating the functions of the proteases is important because expression differs among mast cells in different tissue locations. Differences between laboratory animals and humans in protease expression also influence the degree of confidence with which results obtained in animal models of mast cell function can be extrapolated to humans. The inflammatory potential of mast cell proteases was the first aspect of their biology to be explored and has received the most attention, in part because some of them, notably tryptases and chymases, are biomarkers of local and systemic mast cell degranulation and anaphylaxis. Although some of the proteases indeed augment allergic inflammation and are potential targets for inhibition to treat asthma and related allergic disorders, they are protective and even anti-inflammatory in some settings. For example, mast cell tryptases may protect from serious bacterial lung infections and may limit the "rubor" component of inflammation caused by vasodilating neuropeptides in the skin. Chymases help to maintain intestinal barrier function and to expel parasitic worms and may support blood pressure during anaphylaxis by generating angiotensin II. In other life-or-death examples, carboxypeptidase A3 and other mast cell peptidases limit systemic toxicity of endogenous peptideslike endothelin and neurotensin during septic peritonitis and inactivate venom-associated peptides. On the other hand, mast cell peptidase-mediated destruction of protective cytokines, like IL-6, can enhance mortality from sepsis. Peptidases released from mast cells also influence nonmast cell proteases, such as by activating matrix metalloproteinase cascades, which are important in responses to infection and resolution of tissue injury. Overall, mast cell proteases have a variety of roles, inflammatory and anti-inflammatory, protective and deleterious, in keeping with the increasingly well-appreciated contributions of mast cells in allergy, tissue homeostasis and innate immunity.

Role of chymase in cigarette smoke-induced pulmonary artery remodeling and pulmonary hypertension in hamsters

Background

Cigarette smoking is an important risk factor for pulmonary arterial hypertension (PAH) in chronic obstructive pulmonary disease (COPD). Chymase has been shown to function in the enzymatic production of angiotensin II (AngII) and the activation of transforming growth factor (TGF)-β1 in the cardiovascular system. The aim of this study was to determine the potential role of chymase in cigarette smoke-induced pulmonary artery remodeling and PAH.

Methods

Hamsters were exposed to cigarette smoke; after 4 months, lung morphology and tissue biochemical changes were examined using immunohistochemistry, Western blotting, radioimmunoassay and reverse-transcription polymerase chain reaction.

Results

Our results show that chronic cigarette smoke exposure significantly induced elevation of right ventricular systolic pressures (RVSP) and medial hypertrophy of pulmonary arterioles in hamsters, concurrent with an increase of chymase activity and synthesis in the lung. Elevated Ang II levels and enhanced TGF-β1/Smad signaling activation were also observed in smoke-exposed lungs. Chymase inhibition with chymostatin reduced the cigarette smoke-induced increase in chymase activity and Ang II concentration in the lung, and attenuated the RVSP elevation and the remodeling of pulmonary arterioles. Chymostatin did not affect angiotensin converting enzyme (ACE) activity in hamster lungs.

Conclusions

These results suggest that chronic cigarette smoke exposure can increase chymase activity and expression in hamster lungs. The capability of activated chymase to induce Ang II formation and TGF-β1 signaling may be part of the mechanism for smoking-induced pulmonary vascular remodeling. Thus, our study implies that blockade of chymase might provide benefits to PAH smokers.

Mast cell proteases: multifaceted regulators of inflammatory disease

Mast cells (MCs) are currently receiving increased attention among the scientific community, largely because of the recent identification of crucial functions for MCs in a variety of disorders. However, it is in many cases not clear exactly how MCs contribute in the respective settings. MCs express extraordinarily high levels of a number of proteases of chymase, tryptase, and carboxypeptidase A type, and these are stored in high amounts as active enzymes in the MC secretory granules. Hence, MC degranulation leads to the massive release of fully active MC proteases, which probably have a major impact on any condition in which MC degranulation occurs. Indeed, the recent generation and evaluation of mouse strains lacking individual MC proteases have indicated crucial contributions of these to a number of different disorders. MC proteases may thus account for many of the effects ascribed to MCs and are currently emerging as promising candidates for treatment of MC-driven disease. In this review, we discuss these findings.

Chymase plays an important role in left ventricular remodeling induced by intermittent hypoxia in mice

Intermittent hypoxia caused by sleep apnea is associated with cardiovascular disease. Chymase has been reported to play an important role in the development of cardiovascular disease, but it is unclear whether chymase is involved in the pathogenesis of left ventricular remodeling induced by intermittent hypoxia. The aim of this study was to evaluate the effect of a novel chymase inhibitor (NK3201) on hypoxia-induced left ventricular remodeling in mice. Male C57BL/6J mice (9 weeks old) were exposed to intermittent hypoxia or normoxia and were treated with NK3201 (10 mg/kg per day) or the vehicle for 10 days. Left ventricular systolic pressure showed no significant differences among all of the experimental groups. Exposure to intermittent hypoxia increased left ventricular chymase activity and angiotensin II expression, which were both suppressed by treatment with NK3201. Intermittent hypoxia also increased the mean cardiomyocyte diameter, perivascular fibrosis, expression of inflammatory cytokines, oxidative stress, and NADPH-dependent superoxide production in the left ventricular myocardium. These changes were all suppressed by NK3201 treatment. Therefore, chymase might play an important role in intermittent hypoxia-induced left ventricular remodeling, which is independent of the systemic blood pressure.

Identification of 6-substituted 4-arylsulfonyl-1,4-diazepane-2,5-diones as a novel scaffold for human chymase inhibitors

A novel series of 6-substituted 4-sulfonyl-1,4-diazepane-2,5-diones were designed, synthesized and evaluated as human chymase inhibitors. Structure-activity relationship studies led to the identification of a potent inhibitor, (6S)-6-(5-chloro-2-methoxybenzyl)-4-[(4-chlorophenyl)sulfonyl]-1,4-diazepane-2,5-dione, with an IC(50) of 0.027 microM.

Mast Cell Proteases

Mast cells (MCs) are traditionally thought of as a nuisance for its host, for example, by causing many of the symptoms associated with allergic reactions. In addition, recent research has put focus on MCs for displaying harmful effects during various autoimmune disorders. On the other hand, MCs can also be beneficial for its host, for example, by contributing to the defense against insults such as bacteria, parasites, and snake venom toxins. When the MC is challenged by an external stimulus, it may respond by degranulation. In this process, a number of powerful preformed inflammatory "mediators" are released, including cytokines, histamine, serglycin proteoglycans, and several MC-specific proteases: chymases, tryptases, and carboxypeptidase A. Although the exact effector mechanism(s) by which MCs carry out their either beneficial or harmful effects in vivo are in large parts unknown, it is reasonable to assume that these mediators may contribute in profound ways. Among the various MC mediators, the exact biological function of the MC proteases has for a long time been relatively obscure. However, recent progress involving successful genetic targeting of several MC protease genes has generated powerful tools, which will enable us to unravel the role of the MC proteases both in normal physiology as well as in pathological settings. This chapter summarizes the current knowledge of the biology of the MC proteases.

Therapeutic potential of sulfamides as enzyme inhibitors

Sulfamide, a quite simple molecule incorporating the sulfonamide functionality, widely used by medicinal chemists for the design of a host of biologically active derivatives with pharmacological applications, may give rise to at least five types of derivatives, by substituting one to four hydrogen atoms present in it, which show specific biological activities. Recently, some of these compounds started to be exploited for the design of many types of therapeutic agents. Among the enzymes for which sulfamide-based inhibitors were designed, are the carbonic anhydrases (CAs), a large number of proteases belonging to the aspartic protease (HIV-1 protease, gamma-secretase), serine protease (elastase, chymase, tryptase, and thrombin among others), and metalloprotease (carboxypeptidase A (CPA) and matrix metalloproteinases (MMP)) families. Some steroid sulfatase (STS) and protein tyrosine phosphatase inhibitors belonging to the sulfamide class of derivatives have also been reported. In all these compounds, many of which show low nanomolar affinity for the target enzymes for which they have been designed, the free or substituted sulfamide moiety plays important roles for the binding of the inhibitor to the active site cavity, either by directly coordinating to a metal ion found in some metalloenzymes (CAs, CPA, STS), usually by means of one of the nitrogen atoms present in the sulfamide motif, or as in the case of the cyclic sulfamides acting as HIV protease inhibitors, interacting with the catalytically critical aspartic acid residues of the active site by means of an oxygen atom belonging to the HN-SO2-NH motif, which substitutes a catalytically essential water molecule. In other cases, the sulfamide moiety is important for inducing desired physico-chemical properties to the drug-like compounds incorporating it, such as enhanced water solubility, better bioavailability, etc., because of the intrinsic properties of this highly polarized moiety when attached to an organic scaffold. This interesting motif is thus of great value for the design of pharmacological agents with a lot of applications.

Chymase: a new pharmacologic target in cardiovascular disease

Chymase is a chymotrypsin-like serine protease stored as an inactive enzyme within the secretory granules of mast cells. An important action of chymase is the angiotensin-converting enzyme (ACE)-independent synthesis of angiotensin II, which occurs immediately after its release into the interstitial tissues after vascular injury. Under physiological conditions, the role of chymase is uncertain, but under pathologic situations, chymase may have an important role. Pharmacologic strategies that serve to inhibit chymase function may prove to be useful in the setting of vascular injury.

Physiology of Local Renin-Angiotensin Systems

Since the first identification of renin by Tigerstedt and Bergmann in 1898, the renin-angiotensin system (RAS) has been extensively studied. The current view of the system is characterized by an increased complexity, as evidenced by the discovery of new functional components and pathways of the RAS. In recent years, the pathophysiological implications of the system have been the main focus of attention, and inhibitors of the RAS such as angiotensin-converting enzyme (ACE) inhibitors and angiotensin (ANG) II receptor blockers have become important clinical tools in the treatment of cardiovascular and renal diseases such as hypertension, heart failure, and diabetic nephropathy. Nevertheless, the tissue RAS also plays an important role in mediating diverse physiological functions. These focus not only on the classical actions of ANG on the cardiovascular system, namely, the maintenance of cardiovascular homeostasis, but also on other functions. Recently, the research efforts studying these noncardiovascular effects of the RAS have intensified, and a large body of data are now available to support the existence of numerous organ-based RAS exerting diverse physiological effects. ANG II has direct effects at the cellular level and can influence, for example, cell growth and differentiation, but also may play a role as a mediator of apoptosis. These universal paracrine and autocrine actions may be important in many organ systems and can mediate important physiological stimuli. Transgenic overexpression and knock-out strategies of RAS genes in animals have also shown a central functional role of the RAS in prenatal development. Taken together, these findings may become increasingly important in the study of organ physiology but also for a fresh look at the implications of these findings for organ pathophysiology.

Cromolyn administration (to block mast cell degranulation) reduces necrosis of dystrophic muscle in mdx mice

Duchenne muscular dystrophy is a lethal muscle wasting disorder, resulting from mutations in the gene encoding for the skeletal muscle protein dystrophin. The absence of functional dystrophin leaves the muscle membrane vulnerable to damage during contraction. Damage initially occurs as 'tears' in the membrane, this damage can be exacerbated by the inflammatory response leading to myofibre necrosis rather than repair. Mast cells resident within skeletal muscle represent an immediate source of pro-inflammatory cytokines. We hypothesise that blockade of mast cell degranulation would reduce the extent of myofibre necrosis in the mdx mouse. Daily cromolyn injections were performed on young and exercised adult mdx mice and histological analysis confirmed that mast cell degranulation contributes to myofibre necrosis. This research identified high biological variation between individual mdx mice in the severity of the dystrophic pathology, and supported a relationship between extent of muscle damage in adult mdx mice and their individual enthusiasm for voluntary wheel running.

Chymase inhibition prevents cardiac fibrosis and dysfunction after myocardial infarction in rats

Human chymase activates not only angiotensin II but also transforming growth factor-beta, a major stimulator of myocardial fibrosis, while rat chymase activates transforming growth factor-beta, but not angiotensin II. To clarify the role of chymase-dependent transforming growth factor-beta activation, we evaluated whether chymase inhibition prevents cardiac fibrosis and cardiac dysfunction after myocardial infarction in rats. Myocardial infarction was induced by ligation of the left anterior descending coronary artery. One day after the ligation, rats were randomized into 2 groups: 1) a chymase-treated group that received 10 mg/kg per day of the chymase inhibitor NK3201 orally for 4 weeks; and 2) a vehicle group of non-treated rats with myocardial infarction. We also included a control group who underwent sham-operation and no treatment. Four weeks after ligation, echocardiography revealed that chymase inhibitor treatment reduced the akinetic area and increased fractional area change but did not significantly change left ventricular end-diastolic area. Chymase inhibition significantly reduced left ventricular end-diastolic pressure, increased the maximal end-systolic pressure-volume relationship and decreased the time constant of left ventricular relaxation. Chymase activity in the non-infarcted myocardium was significantly increased in the vehicle group, but it was significantly reduced by chymase inhibitor treatment. The fibrotic area in the cardiac tissues and the mRNA levels of collagen I and collagen III were also significantly lower in the chymase inhibitor-treated group than in the vehicle group. Therefore, the pathway forming chymase-dependent transforming growth factor-beta may play an important role in myocardial fibrosis and cardiac dysfunction rather than left ventricular dilatation after myocardial infarction.

Advanced glycation end products activate a chymase-dependent angiotensin II-generating pathway in diabetic complications

BACKGROUND

Angiotensin II is a key mediator of diabetes-related vascular disease. It is now recognized that in addition to angiotensin-converting enzyme, chymase is an important alternative angiotensin II-generating enzyme in hypertension and diabetes. However, the mechanism of induction of chymase in diabetes remains unknown.

METHODS AND RESULTS

Here, we report that chymase is upregulated in coronary and renal arteries in patients with diabetes by immunohistochemistry. Upregulation of vascular chymase is associated with deposition of advanced glycation end products (AGEs), an increase in expression of the receptor for AGEs (RAGE), and activation of ERK1/2 MAP kinase. In vitro, AGEs can induce chymase expression and chymase-dependent angiotensin II generation in human vascular smooth muscle cells via the RAGE-ERK1/2 MAP kinase-dependent mechanism. This is confirmed by blockade of AGE-induced vascular chymase expression with a neutralizing RAGE antibody and an inhibitor to ERK1/2 and by overexpression of the dominant negative ERK1/2. Compared with angiotensin-converting enzyme, chymase contributes to the majority of angiotensin II production (>70%, P<0.01) in response to AGEs. Furthermore, AGE-induced angiotensin II production is blocked by the anti-RAGE antibody and by inhibition of ERK1/2 MAP kinase activities.

CONCLUSIONS

AGEs, a hallmark of diabetes, induce chymase via the RAGE-ERK1/2 MAP kinase pathway. Chymase initiates an important alternative angiotensin II-generating pathway in diabetes and may play a critical role in diabetic vascular disease.

Therapeutic strategies against TGF-beta signaling pathway in hepatic fibrosis

Hepatic fibrosis is the common wound-healing response to chronic liver injury. In this process, activation of hepatic stellate cells is characteristic of cell proliferation and migration, production of collagen and other extracellular matrix (ECM) molecules, and contraction after transforming into myofibroblasts. It has been shown that the fibrogenic process is prominently regulated by transforming growth factor-beta1 (TGF-beta1) and that the specific blockade of TGF-beta1/Smad3 signaling may therapeutically intervene the fibrosis of various tissues. In this review, we attempt to integrate recent advances in the understanding of the mechanisms underlying TGF-beta1/Smad3 pathway modulation of ECM gene expression in the context of liver fibrosis, discuss intervention strategies targeting the blockade of related signal pathways, and look into novel ways to the safe and efficacious prevention and treatment of hepatic fibrosis.