Prakash, Y.S.

Abstract Asthma in the elderly (AIE) represents a unique challenge, necessitating better understanding of the mechanisms that drive airway hyperreactivity and remodeling (thickened, fibrotic airways). Normal aging is associated with increased lung stiffness, and thus the influence of mechanical forces on bronchial airways (breathing, sighs, CPAP) likely changes, potentially increasing with AIE and resultant remodeling, overall highlighting the need to understand the importance of mechanobiology in aging and AIE. Here, mechanosensitive Piezo (Pz) channels are highly expressed in the lung, including within airway epithelium and smooth muscle (ASM) but their specific roles particularly with aging remain largely unexplored. In this study, we used human ASM cells from young vs. old (≥65 y) non-asthmatics vs asthmatics to test the hypothesis that normal aging blunts Pz expression and functionality at baseline as well as in response to mechanical stretch, whereas asthma, particularly, AIE ASM leads to enhanced Pz expression promoting fibrosis and remodeling. Both Pz1 and Pz2 were expressed in ASM and increased in AIE. Oscillatory mechanical stretch mimicking breathing with superimposed static stretch increased Pz, especially in AIE: effects exacerbated by Pz activator Yoda1 and blunted by Pz inhibitor GsMTx4. Stretch or Yoda1 increased Wnt3a, β-catenin and GSK3β activation particularly in AIE, while ASM proliferation and extracellular matrix production remained preserved or even heightened in elderly ASM. Conversely, Pz1 inhibition by GsMTx4 potently reduced ECM deposition, particularly in AIE cells, highlighting Pz1's pivotal role in modulating ECM deposition. Overall, our findings indicate Pz1 as a mechanosensitive regulator of airway remodeling in AIE.

Abstract Rationale: While survival of premature infants has improved with NICU interventions, prematurity remains a risk for developing chronic lung diseases. Oxygen supplementation in the NICU is unfortunately necessary, and clinical practice has shifted towards use of moderate hyperoxia (<60% O2) to minimize detrimental effects of very high O2 concentration (80-90%) such as bronchopulmonary dysplasia. However, even moderate hyperoxia increases the risk of bronchial airway diseases and wheezing/asthma with airway hyperreactivity and remodeling. We previously found that moderate hyperoxia induces cellular senescence in human fetal airway smooth muscle cells (fASM) and fibroblasts. However, the mechanisms by which hyperoxia enhances cellular senescence in fASM are not known. We investigated the role of endoplasmic reticulum (ER) stress and mitochondrial dysfunction, using fASM cells exposed to 21% (normoxia) vs. 50% O2 (hyperoxia). Methods: fASM isolated from lungs of 18-20 week aborted fetuses (Mayo IRB exempt; period of rapid bronchial airway growth) were exposed to normoxia, hyperoxia or etoposide (10 µM; positive control for senescence induction). Cells and lysates were harvested at days 2, 3 or 7 to assess markers of senescence markers, ER stress and mitochondrial morphology, and levels of cytosolic and mitochondrial ROS, using real-time fluorescence imaging, Western blotting, immunofluorescence, and a novel immuno-FISH staining of telomere associated foci (TAF). Mitochondria-specific antioxidant MitoQ [100 nM], ER stress inhibitor Salubrinal [12.5 µM] or mitochondrial fission inhibitor Mdivi-1 [10 µM] were used to assess their effects on senescence markers and interactions between ER stress and mitochondria in inducing senescence. Results: Hyperoxia enhanced cellular senescence via upregulation of p21, PAI-1, and Cav-1; downregulation of LMNB1 and Ki-67, with increased γH2A.X- and TAF-positive cells. Hyperoxia increased cytosolic and mitochondrial ROS, and markers of the three ER stress pathways (ATF6, IRE1α, XBP1s, PDI, GADD34). Hyperoxia altered mitochondrial morphology with increased fission protein Drp1 and fusion proteins Mfn1/2. Inhibition of Drp1 with Mdivi-1 blocked mitochondrial fragmentation, but not senescence. However, hyperoxia-induced p21 was reduced by the PERK pathway inhibitor Salubrinal and MitoQ. Conclusions: Hyperoxia induces senescence in fASM via mitochondrial ROS and ER stress: pathways that offer new opportunities to blunt detrimental effects of oxygen in developing lung via mitochondrial targeted antioxidants and/or ER stress inhibition.

Abstract Rationale: The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor and cellular chemical sensor. AhR maintains cellular homeostatsis in respons to endogenous and exogenous organic molecules. Airway smooth muscle (ASM) cells are major structural cells in airway which is involved in characteristic features of asthma such as increased airway wall thickness, airway remodeling and airway hyperresponsiveness. Previously, we found notable expression of AhR in human ASM and its increased expression during inflammation and asthma. However, the mechanisms of enhanced AhR expression in ASM is unknown. Therefore, we examined the role of pro-inflammatory signaling pathways in enhanced AhR expression. Methods: Primary human non-asthmatic and asthmatic ASM cells isolated from surgical lung resections (Mayo IRB approved) were cultured in DMEM-F12 medium supplemented with 10% fetal bovine serum and 1% antibiotic/antimycotic. At ∼80% confluency, cells were serum deprived and treated with TNFα (20 ng/mL), IL13 (50 ng/mL) with or without PI3K/Akt inhibitor (Wortmannin: 50 nM), p38 inhibitor (SB203580: 600 nM), NFkB inhibitor (SN50 20 μM), and AP1 inhibitor (SR11302 10 μM). Subsequently, expression of AhR was determined using RNA sequencing, confocal microscopy, real-time qPCR, and Western blotting. AhR expression in isolated ASM fron lung tissue section was determined using laser capture microdissection (LCM). Moreover, role of AP1 in inducing AhR expression was confirmed using c-JUN (AP1) siRNA transfection in ASM cells. Additionally, binding of AP1 to the AhR promoter region was demonstrated by chromatin-immunoprecipitation (ChIP-qPCR) technique. Results: AhR expression was significantly high in asthmatic ASM cells and tissue than non-asthmatics. Exposure to pro-inflammatory cytokine TNFα increased AhR mRNA and protein expression, whereas IL-13 failed to do so. Furthermore, inhibition of p38 significantly reduced AhR expression whereas PI3K inhibition had no effect, indicating a role for p38 in AhR increased expression. AP1 inhibition significantly downregulated AhR, while NFkB inhibition showed no effect. Similarly, siRNA mediated silencing of c-JUN (AP1) also downregulated AhR, indicating AP1 role in AhR upregulation. Furthermore, transcription factor binding study suggested AhR promoter region has binding site for AP1 and NFkB. Interestingly, ChIP-qPCR study confirmed binding of AP1 at AhR promote region in response to TNFα. Conclusions: Collectively, the current study show that pro-inflammatory cytokine TNFα increases AhR expression through p38-AP1 pathway. The data shows that pro-inflammatory cytokines can regulate AhR expression in ASM, suggesting AhR in ASM has a role in asthma.

Abstract Rationale: Asthma involves airway inflammation, hyperresponsiveness (AHR), and remodeling (cell proliferation and fibrosis), with both aspects not fully alleviated by current therapies. GPCR-based drugs represent a major aspect of current asthma therapy. Asthmatic airways express several orphan receptors with unknown physiological roles, highlighting a potentially novel and significant area for therapeutic exploration. Herein, we focus on orphan retinoic acid (RA)-induced Class C GPCR members GPRC5A (RAIG1; 5A) and GPRC5B (RAIG2; 5B). We leveraged recently identified 5A agonists to test the hypothesis that these GPCRs have alleviating effects in airways. Methods: Primary human airway smooth muscle cells (ASM) originating from non-asthmatic (NA) and asthmatic (Asth) individuals were obtained post-surgery from lung tissues after approval by the Mayo Clinic Institutional Review Board. PRESTO-Tango assay was used to determine 5A and 5B activity. cADDis assay was used to assess cAMP levels. Fluorescence imaging was used to determine calcium regulation. Recently identified 5A agonists [tryptamine, 7 fluoro-tryptamine (7FT), L-tryptophan, N-methyltryptamine, and indole-3-acetic acid] were used in assays, along with RA and 5A vs. 5B siRNAs. Results: PRESTO-Tango assay showed that tryptamine (10/100 µM) and 7FT (1/10/100 µM) increased 5A activity while high concentrations of 7FT (100 µM) increased 5B activity as well. cADDis assay showed 100 µM tryptamine increased cAMP more than 1/10 µM tryptamine and that 10 µM 7FT increased cAMP more than 1/100 µM 7FT in NA ASM.Calcium imaging showed that 5A agonist blunts responses to histamine, especially in Asth ASM. Calcium responses were higher in Asth ASM and 5A siRNA-treated ASM while 5B siRNA had an alleviating effect. Conclusions: Class C GPCRs 5A and 5B interestingly have opposing effects in human ASM towards blunting calcium responses to bronchoconstrictor agonists in the context of asthma. Thus, 5A agonists and 5B antagonists may represent novel GPCR-based approaches in airway diseases.

Abstract Rationale: Moderate hyperoxia (<60% O2) in premature infants promotes bronchial airway hyperresponsiveness (AHR) and impaired bronchodilation involving airway smooth muscle (ASM). Understanding mechanisms by which hyperoxia initiates long-term bronchial airway changes in prematurity is critical for novel therapies for wheezing disorders and asthma in children. Underdeveloped lungs in prematurity have immature antioxidant systems, which may be due to disrupted dynamics that promote susceptibility to oxidative stress from O2. Cytoplasmic and mitochondrial calcium signaling mechanisms and O2 metabolism are pathways highly relevant to ASM and airway disease. We propose that the novel gasotransmitter hydrogen sulfide (H2S) attenuates effects of O2 in developing ASM and hypothesize that hyperoxia in prematurity promotes cellular and mitochondrial calcium signaling dysfunction, effects which are counteracted by H2S.Methods: Human fetal (fASM) cells isolated from tracheobronchial samples of de-identified 18-22 week fetuses following fetal demise (Mayo IRB approved as exempt) were exposed to 21% vs 40% O2. fASM were treated 24-72 hours with H2S donor GYY4137, mitochondrial-specific H2S donor AP39, cystathione-β-synthase (CBS) stabilizer AdoMet, cAMP inhibitors SQ22536 or KT5720, or vehicle control (DMSO). CBS shRNA lentiviral particles were used to generate stable knockdown cell lines. Protein markers were measured by Western blot. Intracellular calcium ([Ca2+]i) was measured using 5μM Fura-2/AM and mitochondrial calcium ([Ca2+]m) with 1μM Rhod-2 AM using fluorescence microscopy. Results: CBS expression was lower in fASM exposed to 40% O2 compared to 21% O2. Lentivirus induced CBS KD was exacerbated by 40% O2. Hyperoxia increased [Ca2+]i and [Ca2+]m response to histamine (10μM) in vehicle and Scr controls compared to normoxia. CBS KD increased [Ca2+]i and [Ca2+]m responses to histamine compared to Scr fASM in 21% O2. CBS KD fASM exposed to hyperoxia showed increased [Ca2+]i and [Ca2+]m responses to histamine, but the effect was not amplified by CBS KD. [Ca2+]i and [Ca2+]m responses to histamine were decreased in normoxia by H2S donors GYY4137 (50μM) and AP39 (100nM) and CBS stabilizer AdoMet (100nM); effects which also blunted hyperoxia induced increases. SQ22536 and KT5720 inhibited effects of AP39 and GYY4137 in hyperoxia. Conclusions:Our findings suggest hyperoxia leads to [Ca2+]i and [Ca2+]m dysfunction in developing airway cells, which can be alleviated through modulation of H2S pathways, offering potential targets for future therapies to blunt hyperoxia effects on bronchoconstriction and bronchodilation. Acknowledgment: Supported by AHA Postdoctoral Fellowship 20POST35210002 (Bartman), NIH R01 HL-056470 (Prakash), and HL-160570 (Pabelick).

Abstract Rationale : Airway remodeling in asthma involves increased airway smooth muscle (ASM) mass, changes to bronchial epithelial cell (BEC) layer, and increased fibrosis. ASM and BECs actively contribute by secreting growth factors and cytokines, regulating extracellular matrix (ECM) composition and enhancing cell proliferation/migration. Altering mechanisms which modulate remodeling presents a key to novel therapeutic strategies. BDNF increases ASM [Ca2+]i and contractility, and potentiates the effects of inflammation. Importantly, studies show that ASM is not only a target, but also a source of BDNF, raising the possibility of local autocrine/paracrine effects. Arginase 1 and 2 are expressed by BECs, but their roles in asthma are still under investigation with studies showing arginase 1 inhibition blunting epithelial remodeling and ASM hyperplasia. Knockdown of appealing targets such as ASM BDNF and epithelial arginases using small interfering RNA (siRNA) is a promising approach to combating inflammatory lung remodeling. Polymer based nanoparticles have been constructed which demonstrate cell-type specificity and high efficiency in delivering siRNA. Thus, we hypothesize that BDNF and arginases are central to airway remodeling and can be targeted via nanopartiacles.Methods: Primary human ASM and BEC cells from non-asthmatic vs. asthmatic individuals were obtained post-surgery from lung tissues after approval Mayo Clinic IRB. PONI-Guan NP were generated using block copolymer engineering. PCR, immunoblotting and ELISA were performed using standard techniques. Contractility studies were conducted in adult mouse precision cut lung slices. In vivo lung function studies were conducted in 6-8 week old mice, with or without mixed allergen (MA) treatment and Scireq Flexivent system. Results: PONI-Guan NP uptake demonstrates cell-type specificity in BEC/ASM co-culture and mouse lung. Arginase I/II and ECM expression is upregulated in BECs when exposed to BDNF and cytokines. In ASM, BDNF is increased in asthmatics compared to non-asthmatic controls; ECM expression is increased in response to BDNF and TNF-α. In BEC, PONI-Guan NP/siRNA inhibits Arg I/II expression, even in the presence of TNF-α. In ASM, TNF-α increases in BDNF secretion and ECM deposition are blunted by NP-delivered siRNA. PCLS and mouse lung function studies show contractility to MCh: effects suppressed by NP-delivered BDNF and Arg I siRNA. Conclusions: Our studies show the importance of BDNF/Arginase pathways in airway remodeling and efficacy of PONI-based siRNA delivery vectors in blunting remodeling processes.