Richard Kim’s research while affiliated with Hunter Medical Research Institute and other places

Although cigarette smoke (CS) and low back pain (LBP) are common worldwide, their correlations and the mechanisms of action remain unclear. We had shown that excessive activation of Mast Cells (MCs) and their proteases play key roles in CS associated diseases, like asthma, chronic obstructive pulmonary disease (COPD), blood coagulation and lung cancer. Previous studies also show that MCs and their proteases induce degenerative musculoskeletal disease. By using mice custom-designed smoke-exposure system, we demonstrated that CS results in intervertebral disc (IVDs) degeneration and the release of MC-restricted tetramer tryptases (TT) inside the IVDs. TT was found to regulate the expression of methyltransferase 14 (METTL14) at the epigenetic level by inducing N6-methyladenosine (m6A) deposition in the 3'-untranslated region (3'-UTR) of the transcript that encodes DIX Domain Containing 1 (DIXDC1). That reaction increases the mRNA stability and expression of Dixdc1. DIXDC1 functionally interacts with 'Disrupted in Schizophrenia-1' (DISC1) to accelerate the degeneration and senescence of nucleus pulposus (NP) cells by activating a canonical Wnt pathway. Our study demonstrates the association between CS, MC-derived TTs, and LBP. These findings raise the possibility that METTL14-medicated DIXDC1 m6A modification could serve as a potential therapeutic target to block the development of degeneration of the NP in LBP patients.

Background Asthma and chronic obstructive pulmonary disease (COPD) are common chronic respiratory diseases, and some patients have overlapping disease features, termed asthma-COPD overlap (ACO). Patients characterized with ACO have increased disease severity, however the mechanisms driving this have not been widely studied. Objective To characterize the phenotypic and transcriptomic features of experimental ACO in mice induced by chronic house dust mite (HDM) extract and cigarette smoke (CS) exposure. Methods Female BALB/c mice were chronically exposed to HDM for 11 weeks to induce experimental asthma, CS for 8 weeks to induce experimental COPD, or both concurrently to induce experimental ACO. Lung inflammation, structural changes, and lung function were assessed. RNA-sequencing was performed on separated airway and parenchymal lung tissues to assess transcriptional changes. Validation of a novel upstream driver SPI1 in experimental ACO was assessed using the pharmacological SPI1 inhibitor, DB2313. Results Experimental ACO recapitulated features of both asthma and COPD, with mixed pulmonary eosinophilic/neutrophilic inflammation, small airway collagen deposition and increased airway hyperresponsiveness (AHR). Transcriptomic analysis identified common and distinct dysregulated gene clusters in airway and parenchymal samples in experimental asthma, COPD, and ACO. Upstream driver analysis revealed increased expression of the transcription factor Spi1. Pharmacological inhibition of SPI1 using DB2313, reduced airway remodeling and AHR in experimental ACO. Conclusion A new experimental model of ACO featuring chronic dual exposures to HDM and CS mimics key disease features observed in patients with ACO and revealed novel disease mechanisms, including upregulation of SPI1, that are amenable to therapy.

The authors have withdrawn this preprint due to erroneous posting.

Toll-like receptor (TLR)7 is known for eliciting immunity against single-stranded RNA viruses. TLR7 was increased in both human and cigarette smoke (CS)-induced experimental chronic obstructive pulmonary disease (COPD). Severity of CS-induced emphysema and COPD was reduced in TLR7-deficient mice whilst inhalation of imiquimod (TLR7-agonist) induced emphysema in naïve mice. Imiquimod-induced emphysema was reduced in mice treated with mast cell stabilizer cromolyn or deficient in mast cell protease-6. Therapeutic treatment with anti-TLR7 monoclonal antibody suppressed CS-induced emphysema, experimental COPD and accumulation of pulmonary mast cells. We demonstrate an unexpected role for TLR7 in mediating emphysema and COPD through mast cell activity.

Severe asthma remains a clinical burden despite the emergence of antibody therapies. Complex disease drivers, which shift between T2, T1 and T17 driven inflammation, termed mixed T cell asthma, likely contribute to ineffective disease control in this population. Here we dissect the mechanisms underlying severe asthma to reveal a potential role (s) for both PI3Kgamma and delta (PI3Kγ and δ) isoform activity in asthmatics with a mixed T cell endotype. A PI3Kγδ gene signature was generated from next generation sequencing of IL-8/GM-CSF-stimulated monocytes where PI3Kγδ signalling was inhibited. This mRNA signature was used to interrogate the Ubiopred database. We observed a strong association between PI3Kγδ pathway activity, severity and mixed eosinophil and neutrophil sputum granulocyte content. To further support a role of PI3Kγδ in a mixed T cell asthma phenotype we demonstrated the following. 1) PI3Kδ-dependent allergen stimulation of mixed T cell activity in grass pollen atopic blood. 2) PI3Kδ-mediated inhibition of IL-5, IFNγ and IL-17 production from asthma patient blood T cells. 3) PI3Kγ mediated signalling was required for activation of asthmatic eosinophil and neutrophil populations. 4) Activity of an inhaled PI3Kγδ dual inhibitor in a rodent in vivo model of steroid resistant allergy/infection on mixed T cell mediator release, granulocyte influx and airways hyperresponsiveness. These data identify a population of mixed T cell asthma patients with increased PI3Kγδ activity and suggest a therapeutic potential of an inhaled PI3K dual inhibitor.

CO2 produced by systemic cellular respiration is hydrated into carbonic acid (H2CO3) that dissociates into H+ and HCO3−. These are transported in the plasma to the lungs where HCO3− is converted back into H2CO3 and CO2 that are expelled through breathing. Evidence suggests that dysfunction of the mechanisms that govern these processes may result in the development of respiratory acidosis (RA) and the cardinal features of severe, steroid-resistant (SSR) asthma. Reduced lung function, which occurs in SSR asthma, impairs removal of volatile H2CO3 and CO2, resulting in acid accumulation and increased arterial PaCO2. Patients with severe asthma often develop complications from increased PaCO2, which skews the PaCO2/HCO3− ratio resulting in increased H+ concentration and reduced pH. We developed three mouse models of respiratory infection and ovalbumin-induced SSR allergic airways disease (SSRAAD) that are highly representative of SSR asthma in humans. We used these models to show a role for impaired homeostatic acid-base balance in SSR asthma. All three infections suppress the induction of the expression of the chloride (Cl−)/HCO− pump, Slc26a4, in the airway mucosa in AAD. Importantly, SSRAAD is associated with increased levels of free H+ ions in bronchoalveolar lavage fluid. Administration of Slc26a4-specific siRNA in steroid-sensitive AAD, which mimics the effect of decreased Slc26a4 responses in SSRAAD, induced RA and steroid-resistant airway inflammation and AHR. Importantly, treatment of RA with NaHCO3 during infection-induced SSRAAD suppressed steroid-resistant AHR. Thus, we have identified a previously unrecognised role for deficient Slc26a4 responses that result in the development of RA and the pathogenesis of SSRAAD.