Elastase and cell matrix interactions in the pathobiology of vascular disease

iNOS Deletion in Alveolar Epithelium Cannot Reverse the Elastase-Induced Emphysema in Mice

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide. In addition to chronic bronchitis and emphysema, patients often develop at least mild pulmonary hypertension (PH). We previously demonstrated that inhibition of inducible nitric oxide synthase (iNOS) prevents and reverses emphysema and PH in mice. Interestingly, strong iNOS upregulation was found in alveolar epithelial type II cells (AECII) in emphysematous murine lungs, and peroxynitrite, which can be formed from iNOS-derived NO, was shown to induce AECII apoptosis in vitro. However, the specific cell type(s) that drive(s) iNOS-dependent lung regeneration in emphysema/PH has (have) not been identified yet.

AIM

we tested whether iNOS knockout in AECII affects established elastase-induced emphysema in mice.

METHODS

four weeks after a single intratracheal instillation of porcine pancreatic elastase for the induction of emphysema and PH, we induced iNOS knockout in AECII in mice, and gave an additional twelve weeks for the potential recovery.

RESULTS

iNOS knockout in AECII did not reduce elastase-induced functional and structural lung changes such as increased lung compliance, decreased mean linear intercept and increased airspace, decreased right ventricular function, increased right ventricular systolic pressure and increased pulmonary vascular muscularization. In vitro, iNOS inhibition did not reduce apoptosis of AECII following exposure to a noxious stimulus.

CONCLUSION

taken together, our data demonstrate that iNOS deletion in AECII is not sufficient for the regeneration of emphysematous murine lungs, and suggest that iNOS expression in pulmonary vascular or stromal cells might be critically important in this regard.

The progression of pulmonary arterial hypertension induced by monocrotaline is characterized by lung nitrosative and oxidative stress, and impaired pulmonary artery reactivity

The time-course of pulmonary arterial hypertension in the monocrotaline (MCT) model was investigated. Male rats were divided into two groups: MCT (received a 60 mg/kg i.p. injection) and control (received saline). The MCT and control groups were further divided into three cohorts, based on the follow-up interval: 1, 2, and 3 weeks. Right ventricle (RV) catheterization was performed and RV hypertrophy (RVH) was estimated. The lungs were used for biochemical, histological, molecular, and immunohistochemical analysis, while pulmonary artery rings were used for vascular reactivity. MCT promoted lung perivascular edema, inflammatory cells exudation, greater neutrophils and lymphocytes profile, and arteriolar wall thickness, compared to CTR group. Increases in pulmonary artery pressure and in RVH were observed in the MCT 2- and 3-week groups. The first week was marked by the presence of nitrosative stress (50% moderate and 33% accentuated staining by nitrotyrosine). These alterations lead to an adaptation of NO production by NO synthase activity after 2 weeks. Oxidative stress was evident in the third week, probably by an imbalance between endothelin-1 receptors, resulting in extracellular matrix remodeling, endothelial dysfunction, and RVH. Also, it was found a reduced pulmonary arterial vasodilatory response to acetylcholine after 2 (55%) and 3 (45%) weeks in MCT groups. The relevance of this study is precisely to show that nitrosative and oxidative stress predominate in distinct time windows of the disease progression.

Molecular pathogenesis and current pathology of pulmonary hypertension

Following its initial description over a century ago, pulmonary arterial hypertension (PAH) continues to challenge researchers committed to understanding its pathobiology and finding a cure. The last two decades have seen major developments in our understanding of the genetics and molecular basis of PAH that drive cells within the pulmonary vascular wall to produce obstructive vascular lesions; presently, the field of PAH research has taken numerous approaches to dissect the complex amalgam of genetic, molecular and inflammatory pathways that interact to initiate and drive disease progression. In this review, we discuss the current understanding of PAH pathology and the role that genetic factors and environmental influences share in the development of vascular lesions and abnormal cell function. We also discuss how animal models can assist in elucidating gene function and the study of novel therapeutics, while at the same time addressing the limitations of the most commonly used rodent models. Novel experimental approaches based on application of next generation sequencing, bioinformatics and epigenetics research are also discussed as these are now being actively used to facilitate the discovery of novel gene mutations and mechanisms that regulate gene expression in PAH. Finally, we touch on recent discoveries concerning the role of inflammation and immunity in PAH pathobiology and how they are being targeted with immunomodulatory agents. We conclude that the field of PAH research is actively expanding and the major challenge in the coming years is to develop a unified theory that incorporates genetic and mechanistic data to address viable areas for disease modifying drugs that can target key processes that regulate the evolution of vascular pathology of PAH.

Abnormal mechanical properties of larger arteries in postmenopausal women with systemic lupus erythematosus

There is limited knowledge of potential defects in arterial wall properties in female systemic lupus erythematosus (SLE) patients without manifest cardiovascular disease (CVD) and significant atherosclerotic lesions. The aim of the present study was to investigate the mechanical properties of larger vessels in these patients and to compare them with healthy controls. B-mode ultrasound was used to assess vessel wall structure and to exclude presence of plaque. The ankle/brachial pressure index was measured to exclude occlusive arterial disease. An ultrasound echo-tracking system was used to determine stiffness of the abdominal aorta, common carotid artery (CCA) and popliteal artery (PA) in 39 female patientswith SLE and 55 female, healthy controls. SLE had an independent effect on stiffening of the CCA ( P = 0.01) and PA ( P = 0.005). In addition, larger vessel diameters were observed in the CCA (P = 0.002) after adjustments for the effects of mean arterial pressure and age. Thus, this investigation demonstrated an increased arterial stiffness and signs of premature vascular ageing in the SLE patients without manifest cardiovascular disease and without significant atherosclerotic lesions. The results of this study indicate that other mechanisms besides atherosclerosis might be involved in the pathogenesis of arterial stiffening in SLE patients.

Differences in acute lung response to elastase instillation in two rodent species may determine differences in severity of emphysema development

Elastase intratracheal instillation induces early emphysema in rodents. However, Syrian Golden hamsters develop more severe emphysema than Sprague-Dawley rats. We have reported species differences in oxidant/antioxidant balance modulating antiprotease function early after instillation. We now hypothesize that other components of the initial lung response to elastase might also be species-dependent. Sprague-Dawley rats and Syrian Golden hamsters received a single dose of pancreatic elastase (0.55 U/100 g body wt) to study acute lung injury biomarkers. Using serum, lung, and bronchoalveolar lavage fluid (BALF) samples, we evaluated changes in alveolar-capillary permeability, alpha 1-antitrypsin (α(1)-AT) concentration and activity, glutathione content, and proinflammatory cytokines. Rats showed a large increase in alveolar-capillary permeability and few hemorrhagic changes, whereas hamsters exhibited large hemorrhagic changes (P < 0.01) and mild transendothelial passage of proteins. Western blots showed a 30-fold increase in BALF α(1)-AT concentration in rats and only a 7-fold increase in hamsters (P < 0.001), with [α(1)-AT-elastase] complexes only in rats, suggesting differences in antiprotease function. This was confirmed by the α(1)-AT bioassay showing 20-fold increase in α(1)-AT activity in rats and only twofold increase in hamsters (P < 0.001). In rats, results were preceded by a 3-, 60-, and 20-fold increase in IL-6, IL-1β, and TNF-α respectively (P < 0.001). In hamsters, only IL-1β and TNF-α showed mild increases. All parameters studied were back to baseline by 4 days. In conclusion, several components of the initial lung response showed species differences. Cytokine release pattern and functional inhibition of α(1)-AT were the most significant components differing among species and could account for differences in susceptibility to elastase.

Induced elastin regeneration by chronically activated smooth muscle cells for targeted aneurysm repair

Elastin breakdown in vascular aneurysms is mediated by cytokines such as tumor necrosis factor alpha (TNF-alpha, which induces vascular smooth muscle cell (SMC) activation and regulates their deposition of matrix. We previously demonstrated that exogenous supplementation with TGF-beta1 (1 ng ml(-1)) and hyaluronan oligomers (0.786 kDa, 0.2 microg ml(-1)) cues the upregulation of elastin matrix synthesis by healthy cultured SMCs. Here, we determine whether these cues likewise enhance elastin matrix synthesis and assembly by TNF-alpha-stimulated SMCs, while restoring their healthy phenotype. Adult rat aortic SMCs were treated with TNF-alpha alone or together with TGF-beta1/hyaluronan oligomeric cues and the release of inflammatory markers were monitored during over a 21 day culture. Biochemical analysis was used to quantify cell proliferation, matrix protein synthesis and cross-linking efficiency, while immunofluorescence and electron microscopy were used to analyze the elastin matrix quality. It was observed that SMC activation with TNF-alpha (10 ng ml(-1)) induced matrix calcification and promoted production of elastolytic MMP-2 and MMP-9. However, these effects were attenuated by the addition of TGF-beta1 and HA oligomer cues to TNF-alpha-stimulated cultures, which also enhanced tropoelastin and collagen production, improved elastin matrix yield and cross-linking, promoted elastin fiber formation and suppressed elastase activity, although the release of MMP-2 and MMP-9 was not affected. Overall, the results suggest that TGF-beta1 and HA oligomers are potentially useful in suppressing SMC activation and inducing regenerative elastin repair within aneurysms.

Bench-to-bedside review: brain-lung interaction in the critically ill--a pending issue revisited

Brain and/or lung injury is the most frequent cause of admission to critical care units and patients in this setting frequently develop multiple organ dysfunction with high rates of morbidity and mortality. Mechanical ventilation is commonly used in the management of these critically ill patients and the consequent inflammatory response, together with other physiological factors, is also thought to be involved in distal organ dysfunction. This peripheral imbalance is based on a multiple-pathway cross-talk between the lungs and other organs, including the brain. Interestingly, acute respiratory distress syndrome survivors frequently present some cognitive deterioration at discharge. Such neurological dysfunction might be a secondary marker of injury and the neuroanatomical substrate for downstream impairment of other organs. Brain-lung interactions have received little attention in the literature, but recent evidence suggests that both the lungs and brain are promoters of inflammation through common mediators. This review addresses the current status of evidence regarding brain-lung interactions, their pathways and current interventions in critically ill patients receiving mechanical ventilation.

Subclinical impairment of arterial mechanics in systemic lupus erythematosus identified by arterial waveform analysis

Structural and functional changes in wall and endothelial components of arterial blood vessels underlie the accelerated vascular disease progression in systemic lupus erythematosus (SLE). Using pulse contour analysis we sought to determine if subclinical vascular abnormalities could be identified in a well-characterised cohort of patients with SLE who had no increase in traditional cardiovascular risk factors. Radial artery pressure waveforms were obtained by applanation tonometry and pressure envelopes were analysed by descriptive and model-based approaches. Waveshape morphology was quantified by a novel eigenvector approach and model-based compliance indices of the large arteries (C1, capacitative arterial compliance) and small arteries (C2, reflective arterial compliance) were derived using a third-order four-element modified Windkessel model. Data were recorded from 30 patients with SLE (mean age 44 +/- 7 years and mean SLAM-R 10 +/- 4) and 19 age-matched control subjects. Significant differences in the lower frequency sinusoidal components of the pressure waveforms were evident between groups (P < 0.05). Both C1 and C2 were significantly reduced in patients with SLE: C1 mean +/- SD 13.5 +/- 4.0 ml/mmHg x 10 versus C1 17.5 +/- 4.8 ml/mmHg x 10 (P = 0.003 in patients vs. controls, respectively) and C2 5.2 +/- 3.4 ml/mmHg x 100 versus C2 9.4 +/- 2.8 ml/mmHg x 100 (P < 0.001 in patients vs. controls, respectively). In this group of SLE patients, without an excess of traditional cardiovascular risk factors and SLAM-R scores indicating mild disease, descriptive and model-based analysis of arterial waveforms identified vascular abnormalities at a preclinical stage.

Elevated Basic Fibroblast Growth Factor Levels in Patients With Pulmonary Arterial Hypertension

STUDY OBJECTIVES

Cellular growth in the vascular wall, including endothelial and smooth-muscle cell proliferation, is recognized as a component of the obstructive vasculopathy observed in the small vessels of the lungs in pulmonary arterial hypertension (PAH). We hypothesized that angiogenic growth factors may have a role in the molecular mechanisms underlying this cellular proliferation.

DESIGN

Case-control study.

SETTING

Multicenter, tertiary care hospitals.

PARTICIPANTS

We studied 117 patients with PAH and 60 control subjects.

MEASUREMENTS

We measured levels of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) in the blood and urine of these subjects using an enzyme-linked immunoassay.

RESULTS

Median levels of urinary and plasma bFGF were significantly higher in patients with PAH compared to normal control subjects. There was a difference in levels of urine and plasma bFGF according to etiology of pulmonary hypertension, with the highest levels seen in patients with primary pulmonary hypertension. Levels of urine or plasma VEGF were not significantly different between patients and control subjects.

CONCLUSION

Patients with PAH have substantial alterations in urine and plasma levels of bFGF. This molecule may have a role as a mitogenic factor in the endothelial and smooth-muscle cell proliferation seen in PAH.

Serum IL-1beta levels in health and disease: a population-based study. 'The InCHIANTI study'

Interleukin-1 plays a role in normal homeostasis and in the inflammatory response which is deemed to be responsible for the development of major chronic diseases that are highly prevalent in the elderly. Aim of this study is to evaluate the factors influencing the serum levels of Interleukin-1 beta, in a large and representative population. Data were from the InCHIANTI project, a study of factors contributing to the decline of mobility in late life, which sampled people living in two sites in the surroundings of Florence. Blood samples were obtained from 1,292 participants and frozen aliquots were stored at -80 degrees C. The serum levels of several cytokines were measured by enzyme linked immunosorbent assay using an ultrasensitive commercial kit. Interleukin-1 beta serum levels were associated with congestive heart failure (p > 0.001) and angina (p = 0.02), with Ca2+ serum levels (p = 0.02), and with a history of dyslipidemia (p = 0.05). We found no association between serum IL-1beta level and age, sex, consumption of cardioactive drugs and serum levels of IL-1Ra, IL-6, sIL-6R, IL-10 and TNF-alpha. Our data could lend support to the hypothesis that IL-1beta is mainly involved in the functional alterations of cardiomyocytes under conditions marked by mononuclear cell infiltration and by downregulation of calcium.

Differences in time-related cardiopulmonary responses to hypoxia in three rat strains

The cardiopulmonary profile of three rat strains (Sprague-Dawley, Wistar and High altitude-sensitive) was compared upon exposure to hypoxia (9% O2) for 0, 7 or 14 days. No differences were observed among the in vitro contractile (ET-1) and relaxant (carbachol) responses of pulmonary artery isolated from the three strains during normoxia. Chronic hypoxia decreased ET-1 contractile responses and diminished relaxant responses to carbachol similarly in all strains. In Sprague-Dawley, Wistar and High altitude-sensitive rats, pulmonary arterial pressure rose time-dependently and was elevated by 108%, 116% and 167%, respectively, after 14 days of hypoxia compared to normoxic controls. Right ventricular hypertrophy was increased by 51%, 93% and 55%, respectively, at 14 days. Hypoxia-induced hypertrophy and medial thickening in the pulmonary vasculature were more pronounced in High altitude-sensitive rats. Sprague-Dawley exhibited hypoxia-induced airway hyperresponsiveness to intravenous methacholine, but there were no hypoxia- or strain-related differences in in vitro tracheal contractility. Although each strain exhibited greater sensitivity for a particular hypoxia-induced parameter, pulmonary vascular functional and structural changes suggest that High altitude-sensitive rats represent a choice model of hypoxia-induced pulmonary hypertension.

Current management of patients with pulmonary hypertension and right ventricular insufficiency

Pulmonary hypertension is a pathologic condition characterized by elevated pulmonary artery pressures and an associated vasculopathy. Primary pulmonary hypertension (PPH) is a rare condition with a sporadic occurrence and a familial form of the disorder. Abnormal vasomotor tone in the pulmonary vasculature results from an imbalance of the action of various vasoconstrictors/ vascular proliferative agents (endothelin and thromboxane) versus vasodilators /anti-proliferative agents (prostacyclin and nitric oxide). The mainstay of outpatient therapy has been the use of digitalis, diuretics, oxygen, and coumadin and the judicious use of vasodilator therapy. Calcium channel blockers in a select group and intravenous prostacyclin have dramatically improved survival for those with primary pulmonary hypertension. Use of prostaglandin I2 (PGI2) in other forms of chronic pulmonary arterial hypertension is not as clear, although evidence of initial beneficial response is promising. Importantly, over the next few years both pharmacologic and nonpharmacologic treatment modalities for pulmonary hypertension may rapidly change as we focus more on the abnormal pulmonary vascular biology and concomitant hemodynamic and neurohormonal milieu.

Chronic allograft vasculopathy: new strategies for drug development

Chronic rejection reflects cumulative trauma to the allograft regardless of its origin. The main histologic feature in chronic rejection in all allografts is proliferative allograft vasculopathy. According to the current paradigm, chronic rejection can be prevented by more intensive and selective immunosuppression. Experimental retransplantation to donor strain suggests that elimination of histoincompatibility does not prevent progression of the disorder after the initial stimulus has been sufficiently strong or long-lasting. In order to design additional sites for intervention after this point of no return, attention has focused on the regulation of the synthesis and/or action of smooth muscle cell growth factors. In several preclinical models, the blocking of growth factor synthesis, blocking of the binding of the growth factors to their receptors, and/or growth factor signaling downstream of the receptor, have successfully been used in the inhibition of the intimal response and allograft vasculopathy. Inhibition of proteolytic enzymes, necessary for smooth muscle cell locomotion, may provide additional sites of intervention. However, on most occasions, the inhibitory effect is incomplete only 30% to 50% of maximal. The future will demonstrate whether several approaches must be applied concomitantly, or whether genes regulating several of these ligands and their receptors simultaneously can be identified and exploited.

Chronic rejection: risk factors, regulation, and possible sites of therapeutic intervention

Clinical chronic rejection corresponds histologically to proliferative allograft vasculopathy. This disorder reflects the cumulative trauma to the allograft regardless of its origin. As a consequence of trauma, inflammation is generated, leading to endothelial and smooth muscle cell activation, smooth muscle replication and migration, and graft arterial intimal thickening. According to the current paradigm, chronic rejection can be avoided by more intensive and selective immunosuppression and by avoiding the known predisposing factors. Retransplantation experiments in experimental animals to donor or F1-strain suggest, however, that elimination of histoincompatibility does not prevent the progression of the disorder once it has been initiated. To design additional sites of intervention after the "point-of-no-return," attention has been focused on the regulation of the synthesis of growth factors, binding of the growth factors to the receptors, and to signalling downstream of the receptor. Also, inhibition of proteolytic enzymes, necessary for the locomotion of the smooth muscle cells, is a possible target. On most occasions, however, the inhibitory effect is at the most 30 to 50% of the maximal, and only the future will show whether several of these approaches must be applied concomitantly or whether genes regulating several of these processes simultaneously can be identified and exploited.