Prevention of bleomycin-induced lung fibrosis via inhibition of the MRTF/SRF transcription pathway

Regulation of the RhoA exchange factor GEF-H1 by profibrotic stimuli through a positive feedback loop involving RhoA, MRTF, and Sp1

RhoA and its effectors, the transcriptional coactivators myocardin-related transcription factor (MRTF) and serum response factor (SRF), control epithelial phenotype and are indispensable for profibrotic epithelial reprogramming during fibrogenesis. Context-dependent control of RhoA and fibrosis-associated changes in its regulators, however, remain incompletely characterized. We previously identified the guanine nucleotide exchange factor GEF-H1 as a central mediator of RhoA activation in renal tubular cells exposed to inflammatory or fibrotic stimuli. Here we found that GEF-H1 expression and phosphorylation were strongly elevated in two animal models of fibrosis. In the Unilateral Ureteral Obstruction mouse kidney fibrosis model, GEF-H1 was upregulated predominantly in the tubular compartment. GEF-H1 was also elevated and phosphorylated in a rat pulmonary artery banding (PAB) model of right ventricular fibrosis. Prolonged stimulation of LLC-PK1 tubular cells with tumor necrosis factor (TNF)-α or transforming growth factor (TGF)-β1 increased GEF-H1 expression and activated a luciferase-coupled GEF-H1 promoter. Knockdown and overexpression studies revealed that these effects were mediated by RhoA, cytoskeleton remodeling, and MRTF, indicative of a positive feedback cycle. Indeed, silencing endogenous GEF-H1 attenuated activation of the GEF-H1 promoter. Of importance, inhibition of MRTF using CCG-1423 prevented GEF-H1 upregulation in both animal models. MRTF-dependent increase in GEF-H1 was prevented by inhibition of the transcription factor Sp1, and mutating putative Sp1 binding sites in the GEF-H1 promoter eliminated its MRTF-dependent activation. As the GEF-H1/RhoA axis is key for fibrogenesis, this novel MRTF/Sp1-dependent regulation of GEF-H1 abundance represents a potential target for reducing renal and cardiac fibrosis.NEW & NOTEWORTHY We show that expression of the RhoA regulator GEF-H1 is upregulated in tubular cells exposed to fibrogenic cytokines and in animal models of kidney and heart fibrosis. We identify a pathway wherein GEF-H1/RhoA-dependent MRTF activation through its noncanonical partner Sp1 upregulates GEF-H1. Our data reveal the existence of a positive feedback cycle that enhances Rho signaling through control of both GEF-H1 activation and expression. This feedback loop may play an important role in organ fibrosis.

Glycyrrhetinic acid loaded in milk-derived extracellular vesicles for inhalation therapy of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and life-threatening lung disease for which treatment options are limited. Glycyrrhetinic acid (GA) is a triterpenoid with multiple biological effects, such as anti-inflammatory and anti-fibrotic properties. Herein, inhalable milk-derived extracellular vesicles (mEVs) encapsulating GA (mEVs@GA) were screened and evaluated for IPF treatment. The results indicated that the loading efficiency of GA in mEVs@GA was 8.65%. Therapeutic effects of inhalable mEVs@GA were investigated in vitro and in vivo. The mEVs@GA demonstrated superior anti-inflammatory effects on LPS-stimulated MHS cells. Furthermore, repeated noninvasive inhalation delivery of mEVs@GA in bleomycin-induced IPF mice could decrease the levels of transforming growth factors β1 (TGF-β1), Smad3 and inflammatory cytokines IL-6, IL-1β and TNF-α. The mEVs@GA effectively diminished the development of fibrosis and improved pulmonary function in the IPF mice model at a quarter of the dose compared with the pirfenidone oral administration group. Additionally, compared to pirfenidone-loaded mEVs, mEVs@GA demonstrated superior efficacy at the same drug concentration in the pharmacodynamic study. Overall, inhaled mEVs@GA have the potential to serve as an effective therapeutic option in the treatment of IPF.

Glaucoma: Novel antifibrotic therapeutics for the trabecular meshwork

Glaucoma is a chronic and progressive neurodegenerative disease characterized by the loss of retinal ganglion cells and visual field defects, and currently affects around 1% of the world's population. Elevated intraocular pressure (IOP) is the best-known modifiable risk factor and a key therapeutic target in hypertensive glaucoma. The trabecular meshwork (TM) is the main site of aqueous humor outflow resistance and therefore a critical regulator of IOP. Fibrosis, a reparative process characterized by the excessive deposition of extracellular matrix components and contractile myofibroblasts, can impair TM function and contribute to the pathogenesis of primary open-angle glaucoma (POAG) as well as the failure of minimally invasive glaucoma surgery (MIGS) devices. This paper provides a detailed overview of the current anti-fibrotic therapeutics targeting the TM in glaucoma, along with their anti-fibrotic mechanisms, efficacy as well as the current research progress from pre-clinical to clinical studies.

Progranulin inhibits fibrosis by interacting with and up-regulating DNAJC3 during mouse skin wound healing

Scars place a heavy burden on both individuals and society. Our previous study found that reduction of progranulin (PGRN) promotes fibrogenesis in mouse skin wound healing. However, the underlying mechanisms have not been elucidated. Here, we report that PGRN overexpression decreases the expression of profibrotic genes alpha-smooth muscle actin (αSMA), serum response factor (SRF), and connective tissue growth factor (CTGF), thereby inhibiting skin fibrosis during wound repair. Bioinformatics analysis suggested that the heat shock protein (Hsp) 40 superfamily C3 (DNAJC3) is a potential downstream molecule of PGRN. Further experiments showed that PGRN interacts with and upregulates DNAJC3. Moreover, this antifibrotic effect was rescued by DNAJC3 knockdown. In summary, our study suggests that PGRN inhibits fibrosis by interacting with and upregulating DNAJC3 during wound healing in mouse skin. Our study provides a mechanistic explanation of the effect of PGRN on fibrogenesis in skin wound healing.

Inhaled Lipid Nanoparticles Alleviate Established Pulmonary Fibrosis

Pulmonary fibrosis, a sequela of lung injury resulting from severe infection such as severe acute respiratory syndrome-like coronavirus (SARS-CoV-2) infection, is a kind of life-threatening lung disease with limited therapeutic options. Herein, inhalable liposomes encapsulating metformin, a first-line antidiabetic drug that has been reported to effectively reverse pulmonary fibrosis by modulating multiple metabolic pathways, and nintedanib, a well-known antifibrotic drug that has been widely used in the clinic, are developed for pulmonary fibrosis treatment. The composition of liposomes made of neutral, cationic or anionic lipids, and poly(ethylene glycol) (PEG) is optimized by evaluating their retention in the lung after inhalation. Neutral liposomes with suitable PEG shielding are found to be ideal delivery carriers for metformin and nintedanib with significantly prolonged retention in the lung. Moreover, repeated noninvasive aerosol inhalation delivery of metformin and nintedanib loaded liposomes can effectively diminish the development of fibrosis and improve pulmonary function in bleomycin-induced pulmonary fibrosis by promoting myofibroblast deactivation and apoptosis, inhibiting transforming growth factor 1 (TGFβ1) action, suppressing collagen formation, and inducing lipogenic differentiation. Therefore, this work presents a versatile platform with promising clinical translation potential for the noninvasive inhalation delivery of drugs for respiratory disease treatment.

Repurposing of carvedilol to alleviate lung fibrosis in rats: Repressing of TGF-β1/α-SMA/Smad2/3 and STAT3 gene expressions

Idiopathic pulmonary fibrosis (IPF) is the most widely studied interstitial lung disease. IPF eventually leads to respiratory insufficiency, lung cancer, and death. Carvedilol (CAR) is a third-generation β-adrenergic receptor antagonist with α1-blocking effect. CAR demonstrates antifibrotic activities in various experimental models of organ fibrosis.

AIMS

This work is designed to explore the possible alleviating effects of CAR on bleomycin (BLM)-induced lung fibrosis in rats.

MAIN METHODS

The BLM rat model of lung fibrosis was achieved by intratracheal delivery of a single dose of 5 mg/kg of BLM. Seven days following BLM injection, either prednisolone or CAR was orally administered at doses of 10 mg/kg once daily for 21 days to rats. The actions of CAR were evaluated by lung oxidant/antioxidant parameters, protein concentration and total leucocyte count (TLC) in bronchoalveolar lavage fluid (BALF), fibrosis regulator-related genes along with the coexistent lung histological changes.

KEY FINDINGS

CAR effectively decreased lung malondialdehyde level, increased superoxide dismutase activity, declined both protein concentration and TLC in BALF, downregulated TGF-β1/α-SMA/Smad2/3 and STAT3 gene expressions, and repaired the damaged lung tissues.

SIGNIFICANCE

CAR conferred therapeutic potential against BLM-induced lung fibrosis in rats, at least in part, to its antioxidant, anti-inflammatory, and antifibrotic activities. CAR could be utilized as a prospective therapeutic option in patients with lung fibrosis in clinical practice.

Repositioning itraconazole for amelioration of bleomycin-induced pulmonary fibrosis: Targeting HMGB1/TLR4 Axis, NLRP3 inflammasome/NF-κB signaling, and autophagy

BACKGROUND AND AIMS

Bleomycin (BLM) is one of the antitumor medications that had proven efficacy in the treatment of a wide range of malignant conditions. Pulmonary fibrosis which is frequently encountered during the course of bleomycin therapy may significantly reduce the potential efficacy of bleomycin in cancer therapy. This study tested the hypothesis that itraconazole may have mitigating effects on BLM-induced pulmonary fibrosis and tried to delineate the potential mechanisms of these effects.

MATERIALS AND METHODS

In a rat model of pulmonary fibrosis elicited by BLM, the effect of different doses of itraconazole was explored at the biochemical, histopathological, and electron microscopic levels.

KEY FINDINGS

Itraconazole, in a dose-dependent manner, exhibited significant effects on the pro-oxidant/antioxidant balance, the inflammatory consequences, high-mobility group box 1/toll-like receptor-4 Axis, autophagy and nuclear factor kappa B/Nod-like receptor protein 3 inflammasome signaling and alleviated the histopathological, immunohistochemical, and electron microscopic perturbations induced by BLM in the pulmonary tissues.

SIGNIFICANCE

In view of the afore-mentioned data, itraconazole may be a promising drug that efficiently mitigates the deleterious effects of BLM on the pulmonary tissues.

Prevention of bleomycin-induced lung fibrosis via inhibition of the MRTF/SRF transcription pathway

Bleomycin-induced lung fibrosis is a debilitating disease, linked to high morbidity and mortality in chemotherapy patients. The MRTF/SRF transcription pathway has been proposed as a potential therapeutic target, as it is critical for myofibroblast differentiation, a hallmark of fibrosis. In human lung fibroblasts, the MRTF/SRF pathway inhibitor, CCG-257081, effectively decreased mRNA levels of downstream genes: smooth muscle actin and connective tissue growth factor, with IC₅₀ s of 4 and 15 μM, respectively. The ability of CCG-257081 to prevent inflammation and fibrosis, measured via pulmonary collagen content and histopathology, was tested in a murine model of bleomycin-induced lung fibrosis. Animals were given intraperitoneal bleomycin for 4 weeks and concurrently dosed with CCG-257081 (0, 10, 30, and 100 mg/kg PO), a clinical anti-fibrotic (nintedanib) or the clinical standard of care (prednisolone). Mice treated with 100 mg/kg CCG-257081 gained weight vs. vehicle-treated control mice, while those receiving nintedanib and prednisolone lost significant weight. Hydroxyproline content and histological findings in tissue of animals on 100 mg/kg CCG-257081 were not significantly different from naive tissue, indicating successful prevention. Measures of tissue fibrosis were comparable between CCG-257081 and nintedanib, but only the MRTF/SRF inhibitor decreased plasminogen activator inhibitor-1 (PAI-1), a marker linked to fibrosis, in bronchoalveolar lavage fluid. In contrast, prednisolone led to marked increases in lung fibrosis by all metrics. This study demonstrates the potential use of MRTF/SRF inhibitors to prevent bleomycin-induced lung fibrosis in a clinically relevant model of the disease.