Renin angiotensin aldosterone system in pulmonary fibrosis: Pathogenesis to therapeutic possibilities

Pulmonary fibrosis is a devastating lung disease with multifactorial etiology characterized by alveolar injury, fibroblast proliferation and excessive deposition of extracellular matrix proteins, which progressively results in respiratory failure and death. Accumulating evidence from experimental and clinical studies supports a central role of the renin angiotensin aldosterone system (RAAS) in the pathogenesis and progression of idiopathic pulmonary fibrosis. Angiotensin II (Ang II), a key vasoactive peptide of the RAAS mediates pro-inflammatory and pro-fibrotic effects on the lungs, adversely affecting organ function. Recent years have witnessed seminal discoveries in the field of RAAS. Identification of new enzymes, peptides and receptors has led to the development of several novel concepts. Of particular interest is the establishment of a protective axis of the RAAS comprising of Angiotensin converting enzyme 2 (ACE2), Angiotensin-(1-7) [Ang-(1-7)], and the Mas receptor (the ACE2/Ang-(1-7)/Mas axis), and the discovery of a functional role for the Angiotensin type 2 (AT₂) receptor. Herein, we will review our current understanding of the role of RAAS in lung fibrogenesis, provide evidence on the anti-fibrotic actions of the newly recognized RAAS components (the ACE2/Ang-(1-7)/Mas axis and AT₂ receptor), discuss potential strategies and translational efforts to convert this new knowledge into effective therapeutics for PF.

Abstract P272: Involvement of Neuro-Inflammation in the Pathogenesis of MCT-Induced Pulmonary Hypertension

Background: Pulmonary hypertension (PH) is a devastating disease characterized by increase in pulmonary pressure that eventually leads to right heart failure and death. PH is associated with heightened circulatory cytokines and infiltration of inflammatory cells within the diseased lungs. However, involvement of inflammation within the central nervous system (CNS) in PH pathophysiology has never been investigated. Emerging evidence suggest that activated microglial cells and neuro-inflammation within the CNS play an important role in the pathology of several CNS disorders, including resistant hypertension.

Objective: These observations led us to propose the hypothesis that microglial activation and neuro-inflammation in the autonomic brain regions play regulatory role in PH. Minocycline (Mino), an anti-inflammatory antibiotic, which has been reported to inhibit microglial activation in the autonomic brain regions, was used to test this hypothesis.

Methods: PH was induced in adult male rats by a single injection of monocrotaline (MCT; 50mg/kg sc). A subset of MCT-injected animals was infused intracerebroventricularly (ICV) with Mino (20mg/ml). After 4 weeks of treatment, animals were sacrificed for the measurement of physiological and pathological parameters.

Results: ICV infusion of Mino significantly attenuated right ventricular systolic pressure (RVSP; Con: 30.1±5, MCT: 76.1±14, MCT+Mino: 50.1±11 mmHg) and right ventricular hypertrophy (RVH; Con: 0.26±0.02, MCT: 0.49±0.12, MCT+Mino: 0.38+0.1) induced by MCT. MCT administration resulted in ~2 fold increase in microglial cells, predominantly in the hypothalamic paraventricular nucleus (PVN), an effect significantly attenuated by ICV Mino (Con: 4.0±1.0, MCT: 8.6±1.1, MCT+Mino: 5.0±1.0). MCT injection increased pro-inflammatory cytokines [IL-1β (155%), TNF-α (165%) and IL-6 (113%)] and decreased IL-10 (46%) levels in the PVN. However, ICV Mino treatment restored these cytokines to control levels.

Conclusion: Our observations demonstrate that microglial activation in the PVN is involved in PH pathophysiology. They, for the first time, suggest the involvement of neuro-inflammation and autonomic dysregulation in the development and establishment of PH.

Abstract P109: Spiny Mice Are Protected From Myocardial Infarction Induced Cardiac Pathophysiology

Background: Despite the advancement in drug and surgical interventions, myocardial damage and associated cardiac dysfunction lead to heart failure that remains common cause of death following myocardial infarction (MI). Spiny mice (Acomys cahirinus, SM) have been shown to possess regenerating capacity following deep tissue injury without scarring ( Nature 2013 ). This led us to investigate if this regenerative property would also be preserved in the heart.

Methods and Results: Adult CD1 and SM were subject to left anterior descending coronary artery ligation or sham surgeries. Proliferative cells were identified by nuclear incorporation of 5-bromodeoxyuridine (BrdU, daily, i.p.) and injection was started from 3d post MI continued to 2wks post MI. Cardiac function was assessed using echocardiography and MRI. SM exhibited 3-fold smaller infarct size (SM-MI 18.6±3.4% vs CD1-MI 76.2±3.4%, p<0.05) and better contractility measured by ejection fraction (SM-MI 77.1±6.5 vs CD1-MI 24.6±4.6, %, p<0.05) than CD1 mice. SM showed 6-fold increase in BrdU + cells in left ventricle after MI while CD1 mice had 4-fold increase (CD1-sham 11±3.5 vs CD1-MI 44±9.1 and SM-sham 16±9.8 vs SM-MI 101.1±30.9, p<0.05). Though basal cardiac ACE2 activity was not different between CD1 and SM, MI resulted in a 16% decrease in cardiac ACE2 activity in CD1-MI mice but 20% elevation of cardiac ACE2 activity in myocardial tissue in SM-MI.

Conclusions: SM are protected from ischemia induced cardiac damage and dysfunction. This involves increased proliferating cardiac cells and reduction in infarct size. Thus SM could be an ideal animal model for identification of molecular and genetic circuits involved in preservation/regeneration of cardiac function with translational implication to human MI.

Abstract P110: Low Dose Minocycline Lowers BP and Improves Inflammatory Status in Patients with Treatment Resistant Hypertension

Background: About 15% of hypertensive patients have treatment resistant hypertension (TRH), which substantially increases mortality risk. Based on our previous studies and evidence from literature, we have proposed that systemic and neuro-inflammation is crucial in development and establishment of TRH. This study was to test the hypothesis that minocycline (Mino), an anti-inflammatory antibiotic, would lower BP and inflammatory markers in patient with TRH. Selection of Mino was based on our preliminary studies showing that Mino can inhibit systemic inflammation and penetrate the blood brain barrier to attenuate neuroinflammation in addition to its antibiotic effects.

Methods: A total of 29 subjects was recruited for this study. Exclusion and inclusion criteria are described at Clinicaltrials.gov (NCT02133872). Office and ambulatory BP measurements (ABPM) were used to confirm TRH diagnosis and subsequently measured 30d and 60 d after Mino administration (50mg/d). If BP failed to decline after 60 d Mino treatment (50mg/d), Mino was increased to 100mg/d and patients were monitored at 60 d. Circulating high-sensitivity C-reactive protein (hs-CRP), high-mobility group box 1 (HMGB1), and Th17 levels were measured.

Results: Average BP of TRH patients was 149.5/78.5mmHg, 67% responded to 50mg/d Mino and 33% to 100mg/d. ABPM 24h average BP for all m-TRH was <136/69mmHg 60 d after Mino, and ABPM showed systolic and diastolic BP were significantly reduced by 14.5/10.5 mmHg. Plasma HMGB1 levels were 8- and 5-fold higher in TRH than normotensive (N) and controlled hypertensive (CH) patients, respectively (TRH: 45.2±25.10 vs N: 5.5±3.8 and CH: 8.9±10.2, ng/ml, p<0.05). Mino reduced HMGB1 level in TRH (m-TRH 3.0±0.7, ng/ml p<0.05). Furthermore, there were 3-4-fold increases in Th17 cells and 67% increase in hs-CRP levels in TRH patients compared to N and CH. Mino treatment resulted in significant reduction in these parameters and did not change BMI in TRH patients.

Conclusions: This study demonstrates that a low dose Mino has a significant antihypertensive effect and lowers inflammatory markers in TRH patients. Thus, Mino could be considered a promising therapeutic option for TRH patients.

Acromioclavicular Joint Dislocation with Ipsilateral Mid Third Clavicle, Mid Shaft Humerus and Coracoid Process Fracture - A Case Report

INTRODUCTION

The clavicle, humerus and acromioclavicular (AC) joint separately are very commonly involved in traumatic injuries around the shoulder. Acromioclavicular joint dislocation with distal clavicle fracture is a well recognized entity in clinical practice. AC joint dislocation with mid shaft clavicle fracture is uncommon and only few cases have been reported in literature. However, to the best of our knowledge, this is the first case report to describe an acromioclavicular dislocation with ipsilateral mid shaft clavicle, mid shaft humerus and coracoid process fracture. Fractures of the humerus and clavicle along with the acromioclavicular joint dislocation were fixed at the same setting.

CASE REPORT

A 65-year-old male met with a high velocity road traffic accident. Plain radiographs showed displaced mid third clavicle fracture with acromioclavicular joint dislocation with mid shaft humerus fracture. Surgical fixation was planned for humerus with interlocking nail, clavicle with locking plate and acromioclavicular joint with reconstruction of coracoclavicular ligaments. Intraoperatively, coracoid process was found to have a comminuted fracture. The operative plan had to be changed on table as coracoclavicular fixation was not possible. So acromioclavicular joint fixation was done using tension band wiring and the coracoclavicular ligament was repaired using a 2-0 ethibond. The comminuted coracoid fracture was managed conservatively. K wires were removed at 6 weeks. Early mobilization was started.

CONCLUSION

In acromioclavicular joint injuries, clavicle must be evaluated for any injury. Although it is more commonly associated with distal clavicle fractures, it can be associated with middle third clavicle fractures. As plain radiographs, AP view are most of the times insufficient for viewing integrity of coracoid process, either special views like Stryker notch or CT scan may help in diagnosing such concealed injuries. When associated with fractures of the humerus and clavicle, anatomical restoration of acromioclavicular joint along with anatomical reduction and a rigid fixation of associated fractures is essential. Proper rehabilitation protocol is a must for achieving promising results. In our case, we were able to achieve a stable surgical fixation of both the fractures as well as AC joint, which enabled us to start early joint mobilization and rehabilitation.