Inhibition Of PBEF Is A Possible Therapeutic Target For Pulmonary Hypertension

Source : American Thoracic Society

ATS 2012, SAN FRANCISCO – Inhibition of pre-B Cell Colony-Enhancing Factor (PBEF) could be a potential therapeutic target for pulmonary hypertension (PH), according to a preclinical study in an animal model of PH.

"PBEF expression appears to be significantly increased in PH. Accordingly, we examined whether inhibiting PBEF could prevent and reverse PH in rats," said Roberto Machado, MD, associate professor of medicine at the University of Illinois at Chicago. "We found that PBEF not only prevented the development of PH, but was able to reverse established PH, suggesting its potential use as a therapy for PH in humans."

The results will be presented at the ATS 2012 International Conference in San Francisco.

In the study, rats were given one dose of monocrotaline to induce PH.Two sets of experiments were performed: prevention experiments,in which inhibition of PBEF was performed simultaneously with administration of monocrotaline, and reversal experiments, in which PBEF inhibition was performed two weeks after administration of monocrotaline when PH was already established in the animals.

In the prevention experiments, inhibition of PBEF prevented the development of PH and right ventricular hypertrophy. In the reversal experiments, inhibition of PBEF reversed established PH. In additional experiments in a cell culture model using human pulmonary arterial smooth muscle cells, treatment with recombinant PBEF enhanced store-operated calcium entry, which is involved in sustained pulmonary vasoconstriction and cell proliferation, suggesting a possible mechanism for the observed effects of PBEF inhibition in PH.

"If the prevention and reversal of PH with PPEF inhibition that we observed in our preclinical model can be replicated in humans, it might offer a new approach to the treatment of patients with PH," said Dr. Machado. "Further studies are needed to confirm and expand upon our early results."

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"Inhibition Of Pre-B Cell Colony-Enhancing Factor (PBEF) Prevents And Reverses Monocrotaline-Induced Pulmonary Hypertension" (Session C17, Tuesday, May 22, 2012: 10:15 a.m., Room 2001-2003, Moscone Center; Abstract 29757)

* Please note that numbers in this release may differ slightly from those in the abstract. Many of these investigations are ongoing; the release represents the most up-to-date data available at press time.

Abstract 29757

Inhibition Of Pre-B Cell Colony-Enhancing Factor (PBEF) Prevents And Reverses Monocrotaline-Induced Pulmonary Hypertension

Type: Scientific Abstract

Category: 18.11 - Pulmonary Hypertension: Experimental – Animal Models, Pathogenesis (PC)

Authors: J. Chen1, Y. Yamamura2, K.M. Shioura1, J. Torres1, A. Yamamura2, Q. Guo2, S. Camp1, C. Evenoski1, Y. Zhao3, A. Desai4, L. Moreno-Vinasco1, J.X.J. Yuan2, J.G.N. Garcia1, R.F. Machado1; 1Institute for Personalized Respiratory Medicine; Section of Pulmonary, Critical Care Medicine, Sleep and Allergy, Department of Medicine, University of Illinois at Chicago - Chicago, IL/US, 2Institute for Personalized Respiratory Medicine; Section of Pulmonary, Critical Care Medicine, Sleep and Allergy, Department of Medicine, Department of Pharmacology, University of Illinois at Chicago - Chicago, IL/US, 3Department of Pharmacology, University of Illinois at Chicago - Chicago, IL/US, 4Institute for Personalized Respiratory Medicine; Section of Cardiology , Department of Medicine, University of Illinois at Chicago - Chicago, IL/US

Abstract Body

Rationale:We have previously shown that PBEF, a cytozyme with extracellular proinflammatory cytokine-like activity and intracellular enzymatic activity as a phosphoribosyltransferase, which regulates intracellular NAD levels, cellular redox state, histone deacetylases and inhibits apoptosis, is significantly upregulated in patients with pulmonary arterial hypertension. We sought to determine whether inhibition of the cytokine and enzymatic activities of PBEF could prevent and reverse monocrotaline (MCT)-induced pulmonary hypertension (PH) in rats. In addition, we hypothesized that PBEF could affect calcium signaling pathways, which play a role in cell proliferation and vascular constriction.

Methods: Male Sprague-Dawley rats (n=6 per group) received one dose of MCT (60 mg/kg, IP). In the prevention experiments, rats were simultaneously administrated FK866 (an inhibitor of PBEF enzymatic activity) (2.5 mg/kg, IP, twice daily for 2wks) or recombinant goat anti-PBEF antibody (20 µg/kg, IP, daily for 2wks). In the reversal experiments, the same doses, frequency and duration of FK866 or PBEF antibodies were given 2wks after MCT. Right ventricular systolic pressure (RVSP) was determined with a pressure transducer catheter. The right ventricle: left ventricle +septum (RV/LV+S) ratio was calculated. In a cell culture model, human pulmonary arterial smooth muscle cells (PASMC) were stimulated with recombinant PBEF (25μg/ml) for 6 hrs and 48 hrs. [Ca2+]cyt was measured in PASMC loaded with fura-2/AM (4μM) by a digital fluorescence microscopy system and cyclopiazonic acid (CPA, a specific Ca2+-ATPase inhibitor) was used to induce store-operated calcium entry (SOCE).

Results: Administration of FK866 or PBEF antibody prevented the development of PH (RVSP (mmHg) 21.04 ± 0.65 [control] vs. 39.33 ± 3.24 [MCT] vs. 23.20 ± 0.95 [MCT+FK866] vs. 29.70± 1.43 [MCT+PBEF Abs], p<0.05) and right ventricular hypertrophy (RVH) (RV/LV+S 0.27±0.0046 vs. 0.50±0.049 vs. 0.31±0.040 vs. 0.33± 0.04, p<0.05). In the reversal experiments, administration of FK866 or PBEF antibody reversed established PH (RVSP [mmHg] 19.77 ± 0.80 [control] vs. 51.24±4.35 [MCT] vs. 34.45 ± 3.49 [MCT+FK866] vs. 33.86 ± 5.00 [MCT+PBEF Abs], p<0.05) and RVH (0.25± 0.0013 vs. 0.60± 0.019 vs. 0.43± 0.022 vs. 0.40±0.022, p<0.01). In normal pulmonary artery smooth muscle cells (PASMC), short (6 hrs) and long (48 hrs) treatment with recombinant PBEF enhanced SOCE which is involved in sustained pulmonary vasoconstriction and PASMC proliferation.

Conclusion: Inhibition of PBEF prevents and reverses MCT-induced PH. PBEF may play a role in vascular remodeling via regulation of calcium signaling pathways. These data suggest that PBEF inhibition could be a potential therapeutic target for PH.

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