Sayyed A. Hamidi

Moderate Pulmonary Arterial Hypertension in Male Mice Lacking the Vasoactive Intestinal Peptide Gene

Background— Vasoactive intestinal peptide (VIP), a pulmonary vasodilator and inhibitor of vascular smooth muscle proliferation, has been reported absent in pulmonary arteries from patients with idiopathic pulmonary arterial hypertension (PAH). We have tested the hypothesis that targeted deletion of the VIP gene may lead to PAH with pulmonary vascular remodeling. Methods and Results— We examined VIP knockout (VIP−/−) mice for evidence of PAH, right ventricular (RV) hypertrophy, and pulmonary vascular remodeling. Relative to wild-type control mice, VIP−/− mice showed moderate RV hypertension, RV hypertrophy confirmed by increased ratio of RV to left ventricle plus septum weight, and enlarged, thickened pulmonary artery and smaller branches with increased muscularization and narrowed lumen. Lung sections also showed perivascular inflammatory cell infiltrates. No systemic hypertension and no arterial hypoxemia existed to explain the PAH. The condition was associated with increased mortality. Both the vascular remodeling and RV remodeling were attenuated after a 4-week treatment with VIP. Conclusions— Deletion of the VIP gene leads to spontaneous expression of moderately severe PAH in mice during air breathing. Although not an exact model of idiopathic PAH, the VIP−/− mouse should be useful for studying molecular mechanisms of PAH and evaluating potential therapeutic agents. VIP replacement therapy holds promise for the treatment of PAH, and mutations of the VIP gene may be a factor in the pathogenesis of idiopathic PAH.

Asthma and pulmonary arterial hypertension: do they share a key mechanism of pathogenesis?

Although largely distinct and seemingly unrelated, asthma and pulmonary arterial hypertension (PAH) have important pathological features in common, including inflammation, smooth muscle contraction and remodelling. We hypothesised that these common features could be explained by one shared mechanism of pathogenesis: activation of the transcription factor NFAT (nuclear factor of activated T-cells). If this concept is validated, it could lead to the introduction of novel therapeutic strategies against both lung disorders. In several experimental models, airway remodelling is accompanied by remodelling of smaller pulmonary arteries, validating the hypothesis of their similar pathogenesis. In addition, lungs of vasoactive intestinal peptide (VIP) knockout mice express airway hyperresponsiveness with airway inflammation and PAH with vascular remodelling, with both sets of pathological findings being reversible with VIP treatment. Preliminary data suggest that absence of the VIP gene leads to activation of the calcineurin–NFAT pathway, and that VIP is probably a physiological inhibitor of this pathway. Enough evidence exists to support the views that asthma and PAH share important pathological features, probably related to NFAT activation, and that VIP may be a physiological modulator of this mechanism.

VIP and endothelin receptor antagonist: an effective combination against experimental pulmonary arterial hypertension.

BackgroundPulmonary Arterial Hypertension (PAH) remains a therapeutic challenge, and the search continues for more effective drugs and drug combinations. We recently reported that deletion of the vasoactive intestinal peptide (VIP) gene caused the spontaneous expression of a PH phenotype that was fully corrected by VIP. The objectives of this investigation were to answer the questions: 1) Can VIP protect against PH in other experimental models? and 2) Does combining VIP with an endothelin (ET) receptor antagonist bosentan enhance its efficacy?MethodsWithin 3 weeks of a single injection of monocrotaline (MCT, s.c.) in Sprague Dawley rats, PAH developed, manifested by pulmonary vascular remodeling, lung inflammation, RV hypertrophy, and death within the next 2 weeks. MCT-injected animals were either untreated, treated with bosentan (p.o.) alone, with VIP (i.p.) alone, or with both together. We selected this particular combination upon finding that VIP down-regulates endothelin receptor expression which is further suppressed by bosentan. Therapeutic outcomes were compared as to hemodynamics, pulmonary vascular pathology, and survival.ResultsTreatment with VIP, every other day for 3 weeks, begun on the same day as MCT, almost totally prevented PAH pathology, and eliminated mortality for 45 days. Begun 3 weeks after MCT, however, VIP only partially reversed PAH pathology, though more effectively than bosentan. Combined therapy with both drugs fully reversed the pathology, while preventing mortality for at least 45 days.Conclusions1) VIP completely prevented and significantly reversed MCT-induced PAH; 2) VIP was more effective than bosentan, probably because it targets a wider range of pro-remodeling pathways; and 3) combination therapy with VIP plus bosentan was more effective than either drug alone, probably because both drugs synergistically suppressed ET-ET receptor pathway.

Clues to VIP function from knockout mice.

Abstract:  We have taken advantage of the availability of vasoactive intestinal polypeptide (VIP) knockout (KO) mice to examine the possible influence of deletion of the VIP gene on: (a) airway reactivity and airway inflammation, as indicators of bronchial asthma; (b) mortality from endotoxemia, a model of septic shock; and (c) the pulmonary circulation. VIP KO mice showed: (a) airway hyperresponsiveness to the cholinergic agonist methacholine, as well as peribronchial and perivascular inflammation; (b) a greater susceptibility to death from endotoxemia; and (c) evidence suggestive of pulmonary hypertension.

Iraq dust is respirable, sharp, and metal-laden and induces lung inflammation with fibrosis in mice via IL-2 upregulation and depletion of regulatory T cells.

Objectives: Determine whether surface dust grab samples taken from a large military base in Iraq are toxic and respirable. Methods: X-ray diffraction for mineral content, x-ray fluorescence for elemental content, in vivo mouse dust challenges for assessment of histological changes, bronchoalveolar lavage for cytokines, polarizing light microscopy for crystals in lung tissue, and Fluorescence Activated Cell Sorting for cell surface and intracellular markers were utilized. Results: Camp Victory, Iraq dust taken during wartime contains respirable particles 2.5 microns in size, constituting particulate matter air pollution. Dust particles are angular and have sharp edges. Trace metals (including titanium) calcium and silicon are present. Mice with airway instillation of dust have polarizable crystals in lung and septate inflammation. Regulatory T cells (CD4+CD25+FOXP3+) are decreased in thymus and spleen. Interleukin-2 (IL-2) is upregulated in bronchoalveolar lavage. Conclusions: Respirable Iraq dust leads to lung inflammation in mice similar to that seen in patients with polarizable crystals, which seem to be titanium.

VIP Gene Deletion in Mice Causes Cardiomyopathy Associated with Upregulation of Heart Failure Genes

Rationale Vasoactive Intestinal Peptide (VIP), a pulmonary vasodilator and inhibitor of vascular smooth muscle proliferation, is absent in pulmonary arteries of patients with idiopathic pulmonary arterial hypertension (PAH). We previously determined that targeted deletion of the VIP gene in mice leads to PAH with pulmonary vascular remodeling and right ventricular (RV) dilatation. Whether the left ventricle is also affected by VIP gene deletion is unknown. In the current study, we examined if VIP knockout mice (VIP−/−) develop both right (RV) and left ventricular (LV) cardiomyopathy, manifested by LV dilatation and systolic dysfunction, as well as overexpression of genes conducive to heart failure. Methods We examined VIP−/−and wild type (WT) mice using Magnetic Resonance Imaging (MRI) for evidence of cardiomyopathy associated with biventricular dilation and wall thickness changes. Lung tissue from VIP−/− and WT mice was subjected to whole-genome gene microarray analysis. Results Lungs from VIP−/− mice showed overexpression of cardiomyopathy genes: Myh1 was upregulated 224 times over WT, and Mylpf was increased 72 fold. Tnnt3 was increased 105 times and tnnc2 181 fold. Hearts were dilated in VIP−/− mice, with thinning of LV wall and increase in RV and LV chamber size, though RV enlargement varied. Weights of VIP−/− mice were consistently lower. Conclusions Critically-important heart failure-related genes are upregulated in VIP−/− mice associated with the spontaneous cardiomyopathy phenotype, involving both left and right ventricles, suggesting that loss of the VIP gene orchestrates a panoply of pathogenic genes which are detrimental to both left and right cardiac homeostasis.

Pharmacogenomics in pulmonary arterial hypertension: Toward a mechanistic, target-based approach to therapy

Pharmacogenomics is the study of how genetic variations influence the response to drugs, by correlating gene expression with the drugs efficacy and toxicity. This concept has recently been successfully applied in oncology. To test its applicability to PAH, we examined two experimental models of the disease: mice with deletion of the Vasoactive Intestinal Peptide gene (VIP-/-); and rats injected with monocrotaline (MCT). Since the two models express comparable phenotypic features, we analyzed their particular gene alterations, with special reference to genes related to pulmonary vasoconstriction, vascular remodeling, and inflammation. We then compared the phenotypic and genotypic responses in each model to treatment with the same drug, VIP. In untreated VIP-/- mice there was over-expression of almost all genes promoting vasoconstriction/proliferation, as well as inflammation, and under-expression of all vasodilator/anti-proliferative genes. As expected, treatment with VIP fully corrected both the key PAH features, and all gene expression alterations. MCT-treated rats showed two distinct sets of alterations. One, similar to that in VIP-/- mice, i.e., tended to promote vascular remodeling and inflammation, e.g., up-regulation of myosin polypeptides, procollagen, and some inflammatory genes. The other was a set of opposite alterations that suggested an effort to modulate the PAH, e.g., up-regulation of the VIP and NOS3 genes. In this model, VIP treatment failed to correct many of the genotypic abnormalities, and, in parallel, incompletely corrected the phenotypic changes as well. This preliminary proof-of-concept study demonstrates the importance of genomic information in determining therapeutic outcome, and thus in selecting personalized therapy. Full validation of the merits of pharmacogenomics must await studies of lungs from patients with different forms of PAH.

VIP Regulates the Development & Proliferation of Treg in vivo in spleen.

BackgroundMounting evidence supports a key role for VIP as an anti-inflammatory agent and promoter of immune tolerance. It suppresses TNF-α and other inflammatory cytokines and chemokines, upregulates anti-inflammatory IL-10, and promotes immune tolerant cells called T regulatory (Treg) cells. VIP KO mice have recently been demonstrated to have spontaneous airway and pulmonary perivascular inflammatory responses, as part of asthma-like and pulmonary hypertension phenotypes, respectively. Both inflammatory responses are correctable with VIP. Focusing on this model, we have now investigated the influence of VIP not only on inflammatory cells but also on Treg cells.MethodsUsing flow cytometric analysis, we examined the relative preponderance of CD25+CD4+ cells and anti-inflammatory Treg cells, in extracts of thymus and spleen from VIP KO mice (5 VIP KO; 5 VIP KO+ VIP; 10 wild-type). This method allowed antibody-based flow cytometric identification of Treg cells using surface markers CD25 and CD4, along with the: 1) intracellular activation marker FoxP3; and 2) Helios, which distinguishes cells of thymic versus splenic derivation.ConclusionsDeletion of the VIP gene results in: 1) CD25+CD4- cell accumulation in the thymus, which is corrected by VIP treatment; 2) more Treg in thymus lacking Foxp3 expression, suggesting VIP is necessary for immune tolerance; and, 3) a tendency towards deficiency of Treg cells in the spleen, which is normalized by VIP treatment. Treg lacking Helios are induced by VIP intrasplenically rather than by migration from the thymus. These results confirm the dual role of VIP as an anti-inflammatory and immune tolerance-promoting agent.

17β-estradiol protects the lung against acute injury: possible mediation by vasoactive intestinal polypeptide.

Beyond their classical role as a class of female sex hormones, estrogens (e.g. 17β-estradiol) exert important biological actions, both protective and undesirable. We have investigated the ability of estradiol to protect the lung in three models of acute injury induced by 1) oxidant stress due to the herbicide paraquat; 2) excitotoxicity, caused by glutamate agonist N-methyl-d-aspartate; and 3) acute alveolar anoxia. We also assessed the role of estrogen receptors (ER) ERα and ERβ and the neuropeptide vasoactive intestinal peptide (VIP) in mediating this protection. Isolated guinea pig or rat lungs were perfused in situ at constant flow and mechanically ventilated. The onset and severity of lung injury were monitored by increases in pulmonary arterial and airway pressures, wet/dry lung weight ratio, and bronchoalveolar lavage fluid protein content. Estradiol was infused into the pulmonary circulation, beginning 10 min before induction of injury and continued for 60-90 min. Lung injury was marked by significant increases in the above measurements, with paraquat producing the most severe, and excitotoxicity the least severe, injury. Estradiol significantly attenuated the injury in each model. Both ER were constitutively expressed and immunohistochemically demonstrable in normal lung, and their selective agonists reduced anoxic injury, the only model in which they were tested. As it protected against injury, estradiol rapidly and significantly stimulated VIP mRNA expression in rat lung. Estradiol attenuated acute lung injury in three experimental models while stimulating VIP gene expression, a known mechanism of lung protection. The up-regulated VIP expression could have partially mediated the protection by estrogen.

Vasoactive Intestinal Peptide Knockout (VIP KO) mouse model of sulfite-sensitive asthma: up-regulation of novel lung carbonyl reductase

BackgroundWe earlier reported spontaneous features of asthma in Vasoactive Intestinal Peptide knockout mice (VIP KO): 1) peribronchiolar airway inflammation, with accumulation of lymphocytes and eosinophils, 2) pro-inflammatory cytokine production of IL-5, IL-6, with IFN-γ, and 3) airway hyper-responsiveness to inhaled methacholine. In human asthma, a phenotype with sulfite sensitivity leads to airway inflammation and hyper-responsiveness to inhaled sulfites, and is associated with upregulation of anti-oxidant protein lung carbonyl reductase. For the present experiments, we examined the role of VIP in modulating anti-oxidant genes and their proteins, including lung carbonyl reductase.ResultsFour male VIP KO mice and four wild-type age- and gender matched mice had lungs examined for whole genome microarray and a proteomics approach using mass spectrometry. The proteomics analysis revealed that a novel variant of anti-oxidant protein lung carbonyl reductase (car3) was uniquely and markedly elevated in the VIP KO mice. RT-PCR indicated that carbonic anhydrase 3, which is an anti-oxidant protein, was elevated in the VIP KO mice.ConclusionsThese data support the concept that VIP influences the endogenous oxidant/antioxidant balance. One potential implication is that VIP and its analogues may be used to treat inflammatory diseases, including asthma.