Doxorubicin-induced upregulation of follistatin-like 3 (FSTL3): a new therapeutic target

Introduction

Doxorubicin (DOX) is among the most used anticancer drugs with associated cardiotoxicity. Follistatin-like 3 (FSTL3), a secreted member of the follistatins family that can selectively bind to members of the TGF-β superfamily, is involved in regulation of cardiac hypertrophy and heart failure. FSTL3 is also upregulated in breast and colorectal cancer tumours, is also an unfavourable prognostic indicator for various cancers.

Purpose

We aim to determine the dual role of FSTL3 in prevention of DOX-induced cardiotoxicity and synergistic anti-cancer effects.

Methods

Human cardiomyocytes (HCMs) were treated with DOX at 1uM (EC50) for 72 hours. Cell viability was assessed via CellTiter-Glo®. Secreted FSTL3 levels, as measured by ELISA (R&D systems). FSTL3 and TGF-β mRNA levels were measured by qPCR. Co-treatment of DOX with human anti-FSTL3 antibodies (Aviva Systems Biology) at 10ug/mL were introduced for 72hrs treatment.

Results

Secreted FSTL3 levels were significantly increased in DOX-treated HCMs at 72hrs compared to control (n=5, p<0.001). Consistently, FSTL3 and TGF-β mRNA levels, in collected HCMs were significantly increased in DOX-treated cells. Co-treatment of DOX with human anti-FSTL3 antibodies at 10ug/mL significantly improved HCM viability compared to IgG control group. Conversely, anti-FSTL3 antibodies provided synergistic anti-cancer effects with DOX: MCF-7 breast cancer cells were significantly reduced when co-treated with DOX and anti-FSTL3 antibody vs. IgG controls.

Conclusion

We show, for the first time, that: 1) FSTL3 is secreted directly from HCMs; 2) FSTL3 levels (both circulating and mRNA) is markedly elevated with DOX treatment; 3) neutralisation of FSTL3 in DOX-treated HCMs, restored HCM viability; and 4) exhibit synergistic anti-cancer effects with DOX. Taken together, FSTL3 is a potential target for dual anti-cancer and cardioprotective effects.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Heart Foundation of Australia Future Leader FellowshipsNSW Ministry of Health EMC FellowshipNSW Ministry of Health Translational Research Grant

Mitochondria-targeted Sulfide Delivery Molecules – New and Novel Players that can Suppress and Reverse Cigarette Smoke-induced Inflammasome Activity

RATIONALE

Cigarette smoke (CS) is the major risk factor in development of chronic obstructive pulmonary disease (COPD). Interventions that can prevent and/or reverse disease are urgently needed. Hydrogen sulfide (H2S) is generated in mitochondria (mt) and crucial in maintaining mt respiration, suppressing oxidative stress/inflammation. Lung H2S levels are reduced after CS exposure. Lung inflammation, mitochondrial damage and oxidative injury are exacerbated as a result of inhibition/silencing of H2S enzymes, suggesting impairment of H2S synthesis/loss of bioavailability is detrimental in COPD and negatively impacts mitochondrial health.

METHODS

We have produced novel mt-targeted H2S donors (mtH2SD) AP39 and RT01 to investigate whether these molecules could suppress and/or reverse CS-induced inflammation and lung injury. To investigate suppression, mice were exposed to CS (or air) for 8 wks (with 1.0 mg/kg). To investigate reversal, mice were exposed to CS for 8 wks followed by either 4 wks rest or continued CS exposure, each with mtH2SD (1.0 mg/kg). Airway inflammation (BALF differential cell counts, IL-1β by ELISA) and lung function were assessed.

RESULTS

Lung H2S levels were reduced and inflammasome activity increased in response to CS exposure. mtH2SD significantly suppressed CS-induced alveolar destruction, fibrosis and improved lung function. mtH2SD treatment reversed CS-induced lung neutrophil, eosinophil and macrophage infiltration, loss of lung function, and partially reversed airway resistance in both models.

CONCLUSIONS

Targeting H2S to mitochondria may be a novel therapeutic approach to prevent and/or reverse mitochondria-driven inflammation and lung injury in COPD and related diseases.

Early-life respiratory bacterial infection-induced chronic lung disease is driven by a novel TLR2/IL-13/miR-21/PI3K-dependent, but MyD88-independent signalling pathway

There is a critical window in early-life where the lung is still maturing and susceptible to infection. Indeed, severe respiratory infections in early-life are a risk factor for the development of chronic lung diseases. The aim of this study was to identify the mechanisms involved.

Neonatal wild-type (WT), TLR2 deficient (−/−), IL-13−/−, MyD88−/− and STAT6−/− mice were infected with the natural mouse bacterial pathogen Chlamydia muridarum, as a model of severe respiratory tract infection in early-life. In some experiments WT mice were treated with miR-21 antagomirs, PI3K inhibitors, or relevant controls during early-life infection. The impact of targeting these specific immune molecules during early-life on infection-induced impairment of lung function and structure were assessed.

Neonatal Chlamydia respiratory infection increased TLR2, IL-13-receptor, miR-21 and PI3K expression and/or activity in the lung. TLR2 signalling induced IL-13-receptor expression, IL-13 signalling induced miR-21 expression and miR-21 increased PI3K activity. TLR2 signalling also increased IL-13+ ILC2s in the lung. TLR2−/− and IL-13−/− mice were protected against infection-induced airway hyperresponsiveness (AHR), but not emphysema-like alveolar enlargement. This TLR2/IL-13 mediated phenotype was independent of MyD88, but dependent on STAT6. Specific targeting of miR-21 prevented AHR but not emphysema. Pan-PI3K inhibition did not affect AHR, but protected against emphysema. Interestingly, early-life infection-induced AHR was steroid insensitive.

This study identifies a novel signalling network that may be targeted for the prevention of the long-term deleterious effects of early-life infection on lung function and structure.

MicroRNA-125a and -b inhibit A20 and MAVS to promote inflammation and impair antiviral response in COPD

Influenza A virus (IAV) infections lead to severe inflammation in the airways. Patients with chronic obstructive pulmonary disease (COPD) characteristically have exaggerated airway inflammation and are more susceptible to infections with severe symptoms and increased mortality. The mechanisms that control inflammation during IAV infection and the mechanisms of immune dysregulation in COPD are unclear. We found that IAV infections lead to increased inflammatory and antiviral responses in primary bronchial epithelial cells (pBECs) from healthy nonsmoking and smoking subjects. In pBECs from COPD patients, infections resulted in exaggerated inflammatory but deficient antiviral responses. A20 is an important negative regulator of NF-κB-mediated inflammatory but not antiviral responses, and A20 expression was reduced in COPD. IAV infection increased the expression of miR-125a or -b, which directly reduced the expression of A20 and mitochondrial antiviral signaling (MAVS), and caused exaggerated inflammation and impaired antiviral responses. These events were replicated in vivo in a mouse model of experimental COPD. Thus, miR-125a or -b and A20 may be targeted therapeutically to inhibit excessive inflammatory responses and enhance antiviral immunity in IAV infections and in COPD.