The endoplasmic reticulum (ER) to Golgi secretory pathway is an elegantly complex process whereby protein cargoes are manufactured, folded, and distributed from the ER to the cisternal layers of the Golgi stack before they are delivered to their final destinations. The export of large bulky cargoes such as procollagen and its trafficking to the Golgi is a sophisticated mechanism requiring TANGO1 (Transport ANd Golgi Organization protein 1. It is also called MIA3 (Melanoma Inhibitory Activity protein 3). TANGO1 has two prominent isoforms, TANGO1-Long and TANGO1-Short, and each isoform has specific functions. On the luminal side, TANGO1-Long has an HSP47 recruitment domain and uses this protein to collect collagen. It can also tether its paralog isoforms cTAGE5 and TALI and along with these proteins enlarges the vesicle to accommodate procollagen. Recent studies show that TANGO1-Long combines retrograde membrane flow with anterograde cargo transport. This complex mechanism is highly activated in fibrosis and promotes the excessive deposition of collagen in the tissues. The therapeutic targeting of TANGO1 may prove successful in the control of fibrotic disorders. This review focuses on TANGO1 and its complex interaction with other procollagen export factors that modulate increased vesicle size to accommodate the export of procollagen.
The composition of extracellular matrix (ECM) is altered during pathologic scarring in damaged organs including the lung. One major change in the ECM involves the cross-linking of collagen, which promotes fibroblast to myofibroblast differentiation. We examined the role of lysyl oxidase (LOX)-like 2 in lung progenitors and fibroblasts cultured from normal or IPF lung samples and in a humanized mouse model of IPF using a monoclonal antibody (Simtuzumab). Primary lung fibroblasts from normal donor lungs and IPF lung explants were examined for expression of LOXL2. Targeting LOXL2 with Simtuzumab on normal and IPF fibroblasts was examined both in vitro and in vivo for synthetic, functional, and profibrotic properties. LOXL2 was increased at transcript and protein level in IPF compared with normal lung samples. In a dose-dependent manner, Simtuzumab enhanced differentiation of fibroblasts into myofibroblasts. Inhibition of LOXL2 also enhanced fibroblast invasion and accelerated the outgrowth of fibroblasts from dissociated human lung cell preparations. Finally, preventative or delayed delivery of Simtuzumab enhanced lung fibrosis in a humanized mouse model of pulmonary fibrosis. Consistent with its failure in a Phase 2 clinical trial, Simtuzumab exhibited no therapeutic efficacy in translational in vitro and in vivo assays.
The isoproterenol (or isoprenaline; ISO)-induced model of myocardial injury provides a non-surgical means of establishing features of dilated cardiomyopathy (DCM) in various species, including left ventricular (LV) inflammation, cardiomyocyte hypertrophy, vascular rarefaction, fibrosis and related dysfunction. However, when established in mice, the progression and severity of the LV fibrosis that manifests in this model can be affected by the exposure time and/or dosing of ISO applied, and by strain when an equivalent exposure time and dose are administered. In this study, we measured the severity of LV fibrosis by biochemical and histological means in 129sv, C57BL/6J and FVB/N mice exposed to repeated ISO (25 mg/kg for 5 days) administration at 14-days post-injury. At the time-point studied, these strains of mice underwent a ~2-fold, ~0.7-fold and ~0.3-fold increase in LV collagen concentration, respectively, compared to their saline-injected controls; whilst 129sv and C57BL/6J mice underwent a corresponding ~7-fold and ~1-fold increase in picrosirius red-stained interstitial LV collagen deposition, respectively. C57BL/6J mice subjected to higher dosing of ISO (50 or 100 mg/kg for 5 days) underwent a ~1.4–1.6-fold increase in picrosirius red-stained interstitial LV collagen deposition and some LV systolic dysfunction at day-14 post-injury, but the fibrosis in these mice was still less severe than that measured in 129sv mice given a lower dose of ISO. These findings highlight that strain-dependent differences in ISO-induced LV fibrosis severity can impact on evaluating pathological features of DCM and the therapeutic effects of anti-fibrotic drugs/strategies in this model.
Background: Lysosomal enzymes are implicated in autophagy and senescence. Hepatic lysosomal enzymes have not been studied in Primary Biliary Cholangitis (PBC). We therefore quantified the activities of lysosomal hydrolases in liver tissue of PBC patients. Methods: We compared enzyme activities in liver tissue from PBC patients with normal livers. Alcoholic liver disease and chronic viral disease served as disease controls. Results: Cathepsin B1 was significantly increased in early PBC (225.1 ± 18.06 mean ± SD, p < 0.0001) and reduced in later stages (66.5 ± 9.7, p = 0.004, controls 130.4 ± 14.9). It was reduced in patients with extensive fibrosis such as alcoholic and viral cirrhosis (p < 0.01 and p = 0.004 respectively) but not in chronic hepatitis. Cathepsin D was increased in early PBC (39 × 103 ± 4.8 SD, p < 0.0001) and less so in later stages (20.1 × 103 ± 3.9, p = 0.05, controls 14.1 × 103 ± 2.9). It was also increased in the presence of histological necro-inflammation in hepatitis. Treatment with ursodeoxycholate (UDCA) restored the abnormal values of enzymes in PBC. Lipid hydrolases mostly paralleled the changes of Cathepsins. Sequential measurements in serum of patients with acute alcoholic hepatitis showed that cathepsin B1 gradually decreases, and esterases increase as aminotransferases improve. Conclusions: The increased activity of lysosomal enzymes in early PBC are possibly on line with increased senescence. Treatment with UDCA restores abnormal values. In chronic liver disease, Cathepsin B1 reduction is associated with fibrosis and increased cathepsin D with necro-inflammation. Abnormalities of lysosomal enzymes indicate impairment of the final stage of autophagy in chronic liver disease.
Idiopathic pulmonary fibrosis (IPF) is a progressive, chronic interstitial lung disease with unknown etiology. Matrix metalloproteinases (MMPs) are involved in fibrotic lung tissues, contributing to the initiation, progression, or resolution of chronic inflammatory disease. In present study, comprehensive changes of MMPs expressions were investigated in IPF by integrative analysis of single-cell transcriptome and bulk transcriptome data. 24 of MMPs were altered and the changes could significantly distinguish IPF from normal subjects and other lung diseases. Among them, MMP1, MMP7 and MMP19 were closely associated to lung functions, susceptibility and alveolar surface density. MMP1 and MMP7 as potential diagnostic indicators, MMP1 and MMP19 as prognostic markers in IPF could accurately predict disease progression. Devolution of MMPs at single-cell resolution, MMP19 was highly expressed in macrophages and markedly interfered with TNF signaling pathway which synchronizes fibrotic microenvironment. MMP19+ macrophages were significantly different from MMP19- macrophages in energy metabolism and immune function. The interaction of MMP19+ macrophages with hyperplastic AT2 was mediated by TNFSF12-TNFRSF12A, and further activated the TNFRSF12A receptor to affect cell glucose metabolism and mitochondrial function. In summary, MMPs has great application potential in the diagnosis, treatment, and prognosis of IPF.
Hepatic stellate cells comprise a minor cell population in the liver, playing a key role in the pathogenesis of hepatic fibrosis. In chronic liver damage, these cells undergo a transition from a quiescent to a highly proliferative phenotype with the capacity to synthesize large quantities of extracellular matrix compounds such as collagens. Because of their pivotal role in liver disease pathogenesis, this hepatic cell population has become the focus of liver research for many years. However, the isolation of these cells is time consuming and requires the trained laboratory personnel. In addition, working with primary cells requires the following of ethical and legal standards and potentially needs the approval from respective authorities. Therefore, continuous growing hepatic stellate cells have become very popular in research laboratories because they are widely available and easy to handle, and allow a continuous supply of materials, and further reduction of lab animal use in biomedical research. This communication provides some general information about immortalized hepatic stellate cell lines from mouse, rats and humans.
Currently, low dose radiotherapy (LDRT) is being tested for treating life-threatening pneumonia in COVID-19 patients. Despite the debates over the clinical use of LDRT, some clinical trials have been completed, and most are still ongoing. Ultraviolet C (UVC) irradiation has been proven to be highly efficient in inactivating the coronaviruses, yet is considerably safer than LDRT. This makes UVC an excellent candidate for treating COVID-19 infection, especially in case of severe pneumonia as well as the post COVID-19 pulmonary fibrosis. However, the major challenge in using UVC is its delivery to the lungs, the target organ of COVID-19, due to its low penetrability through biological tissues. We propose to overcome this challenge (i) by using pulsed UVC technologies which dramatically increase the penetrability of UVC through matter, and (ii) by integrating the pulsed UVC technologies into a laser bronchoscope, thus allowing UVC irradiation to reach deeper into the lungs. Although the exact characteristics of such a treatment should yet to be experimentally defined, this approach might be much safer and not less efficient than LDRT.
