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Pancreatic ductal adenocarcinoma (PDAC) is a highly desmoplastic, aggressive cancer that frequently progresses by liver metastasis1. Cancer-associated fibroblasts (CAF), extracellular matrix (ECM), and type I collagen (Col I) support2–5 or restrain PDAC progression and may impede blood supply and nutrient availability6–8. The dichotomous role of the stroma in PDAC, and the mechanisms through which it influences patient survival and enables desmoplastic cancers escape nutrient limitation remain poorly understood. Here we show that matrix metalloprotease (MMP)-cleaved or intact Col I (cCol I and iCol I, respectively) exert opposing effects on PDAC bioenergetics, macropinocytosis (MP), tumor growth and liver metastasis. While cCol I activates DDR1 (discoidin domain receptor-1)-NF-κB-p62-NRF2 signaling to promote PDAC growth, iCol I triggers DDR1 degradation and restrains PDAC growth. Patients whose tumors are enriched in iCol I and low in DDR1 and NRF2 have improved median survival compared to those enriched in cCol I, DDR1 and NRF2. Inhibition of DDR1-stimulated NF-κB or mitochondrial biogenesis blocked tumorigenesis in wildtype mice but not in mice expressing MMP-resistant Col I. In summary, the diverse effects of tumor stroma on PDAC growth, metastasis, and patient survival are mediated through the Col I-DDR1-NF-κB-NRF2-mitochondrial biogenesis pathway, presenting multiple new opportunities for PDAC therapy.

Alcoholic liver disease (ALD) is a leading cause of cirrhosis in the United States, which is characterized by extensive deposition of extracellular matrix proteins and formation of a fibrous scar. Hepatic stellate cells (HSCs) are the major source of collagen type 1 producing myofibroblasts in ALD fibrosis. However, the mechanism of alcohol‐induced activation of human and mouse HSCs is not fully understood. We compared the gene‐expression profiles of primary cultured human HSCs (hHSCs) isolated from patients with ALD (n = 3) or without underlying liver disease (n = 4) using RNA‐sequencing analysis. Furthermore, the gene‐expression profile of ALD hHSCs was compared with that of alcohol‐activated mHSCs (isolated from intragastric alcohol‐fed mice) or CCl4‐activated mouse HSCs (mHSCs). Comparative transcriptome analysis revealed that ALD hHSCs, in addition to alcohol‐activated and CCl4‐activated mHSCs, share the expression of common HSC activation (Col1a1 [collagen type I alpha 1 chain], Acta1 [actin alpha 1, skeletal muscle], PAI1 [plasminogen activator inhibitor‐1], TIMP1 [tissue inhibitor of metalloproteinase 1], and LOXL2 [lysyl oxidase homolog 2]), indicating that a common mechanism underlies the activation of human and mouse HSCs. Furthermore, alcohol‐activated mHSCs most closely recapitulate the gene‐expression profile of ALD hHSCs. We identified the genes that are similarly and uniquely up‐regulated in primary cultured alcohol‐activated hHSCs and freshly isolated mHSCs, which include CSF1R (macrophage colony‐stimulating factor 1 receptor), PLEK (pleckstrin), LAPTM5 (lysosmal‐associated transmembrane protein 5), CD74 (class I transactivator, the invariant chain), CD53, MMP9 (matrix metallopeptidase 9), CD14, CTSS (cathepsin S), TYROBP (TYRO protein tyrosine kinase‐binding protein), and ITGB2 (integrin beta‐2), and other genes (compared with CCl4‐activated mHSCs). Conclusion: We identified genes in alcohol‐activated mHSCs from intragastric alcohol‐fed mice that are largely consistent with the gene‐expression profile of primary cultured hHSCs from patients with ALD. These genes are unique to alcohol‐induced HSC activation in two species, and therefore may become targets or readout for antifibrotic therapy in experimental models of ALD., We identified genes in alcohol‐activated mHSCs from IG alcohol‐fed mice that are largely consistent with the gene‐expression profile of primary cultured hHSCs from patients with ALD. These genes are unique to alcohol‐induced HSC activation in two species, and therefore may become targets or readout for antifibrotic therapy in experimental models of ALD.

We investigated the role of mesothelin (Msln) and thymocyte differentiation antigen 1 (Thy1) in the activation of fibroblasts across multiple organs and demonstrated that Msln(−/−) mice are protected from cholestatic fibrosis caused by Mdr2 (multidrug resistance gene 2) deficiency, bleomycin-induced lung fibrosis, and UUO (unilateral urinary obstruction)-induced kidney fibrosis. On the contrary, Thy1(−/−) mice are more susceptible to fibrosis, suggesting that a Msln–Thy1 signaling complex is critical for tissue fibroblast activation. A similar mechanism was observed in human activated portal fibroblasts (aPFs). Targeting of human MSLN(+) aPFs with two anti-MSLN immunotoxins killed fibroblasts engineered to express human mesothelin and reduced collagen deposition in livers of bile duct ligation (BDL)–injured mice. We provide evidence that antimesothelin-based therapy may be a strategy for treatment of parenchymal organ fibrosis.

We investigated the role of mesothelin (Msln) and thymocyte differentiation antigen 1 (Thy1) in the activation of fibroblasts across multiple organs and demonstrated that Msln-/- mice are protected from cholestatic fibrosis caused by Mdr2 (multidrug resistance gene 2) deficiency, bleomycin-induced lung fibrosis, and UUO (unilateral urinary obstruction)-induced kidney fibrosis. On the contrary, Thy1-/- mice are more susceptible to fibrosis, suggesting that a Msln-Thy1 signaling complex is critical for tissue fibroblast activation. A similar mechanism was observed in human activated portal fibroblasts (aPFs). Targeting of human MSLN+ aPFs with two anti-MSLN immunotoxins killed fibroblasts engineered to express human mesothelin and reduced collagen deposition in livers of bile duct ligation (BDL)-injured mice. We provide evidence that antimesothelin-based therapy may be a strategy for treatment of parenchymal organ fibrosis.

Although hepatocellular cancer (HCC) usually occurs in the setting of liver fibrosis, the causal relationship between liver fibrosis and HCC is unclear. in vivo and in vitro models of HCC involving Col(r/r) mice (that produce a collagenase-resistant type I collagen) or wild-type (WT) mice were used to assess the relationship between type I collagen, liver fibrosis, and experimental HCC. HCC was either chemically induced in WT and Col(r/r) mice or Hepa 1-6 cells were engrafted into WT and Col(r/r) livers. The effect of hepatic stellate cells (HSCs) from WT and Col(r/r) mice on the growth of Hepa 1-6 cells was studied by using multicellular tumor spheroids and xenografts. Collagen type I deposition and fibrosis were increased in Col(r/r) mice, but they developed fewer and smaller tumors. Hepa 1-6 cells had reduced tumor growth in the livers of Col(r/r) mice. Although Col(r/r) HSCs exhibited a more activated phenotype, Hepa 1-6 growth and malignancy were suppressed in multicellular tumor spheroids and in xenografts containing Col(r/r) HSCs. Treatment with vitronectin, which mimics the presence of degraded collagen fragments, converted the Col(r/r) phenotype into a WT phenotype. Although Col(r/r) mice have increased liver fibrosis, they exhibited decreased HCC in several models. Thus, increased liver type I collagen does not produce increased experimental HCC.

Liver fibrosis is a clinically significant finding that has major impacts on patient morbidity and mortality. The mechanism of fibrosis involves many different cellular pathways, but the major cell type involved appears to be hepatic stellate cells. Many liver diseases, including Hepatitis B, C, and fatty liver disease cause ongoing hepatocellular damage leading to liver fibrosis. No matter the cause of liver disease, liver-related mortality increases exponentially with increasing fibrosis. The progression to cirrhosis brings more dramatic mortality and higher incidence of hepatocellular carcinoma. Fibrosis can also affect outcomes following liver transplantation in adult and pediatric patients and require retransplantation. Drugs exist to treat Hepatitis B and C that reverse fibrosis in patients with those viral diseases, but there are currently no therapies to directly treat liver fibrosis. Several mouse models of chronic liver diseases have been successfully reversed using novel drug targets with current therapies focusing mostly on prevention of myofibroblast activation. Further research in these areas could lead to development of drugs to treat fibrosis, which will have invaluable impact on patient survival. This article is categorized under: Metabolic Diseases > Molecular and Cellular Physiology.

Hepatic fibrogenesis is a pathophysiological outcome of chronic liver injury hallmarked by excessive accumulation of extracellular matrix proteins. Fibrosis is a dynamic process that involves cross-talk between parenchymal cells (hepatocytes), hepatic stellate cells, sinusoidal endothelial cells and both resident and infiltrating immune cells. In this review, we focus on key cell-types that contribute to liver fibrosis, cytokines, and chemokines influencing this process and what it takes for fibrosis to regress. We discuss how mitochondria and metabolic changes in hepatic stellate cells modulate the fibrogenic process. We also briefly review how the presence of fibrosis affects development of hepatocellular carcinoma.Impact statementAdvanced liver fibrosis results in cirrhosis, portal hypertension, and liver failure and often requires liver transplantation. Advanced liver fibrosis and cirrhosis are also major risk factors for hepatocellular carcinoma (HCC). Hepatic stellate cells (HSCs) play a pivotal role in the pathogenesis of liver fibrosis. In this review, we summarize the basic mechanisms that influence liver fibrosis development and how oxidative stress, mitochondrial dysfunction, and metabolic remodeling modulate HSC activation and indicate areas of potential therapeutic intervention.

Chronic alcohol abuse has a detrimental effect on the brain and liver. There is no effective treatment for these patients, and the mechanism underlying alcohol addiction and consequent alcohol-induced damage of the liver/brain axis remains unresolved. We compared experimental models of alcoholic liver disease (ALD) and alcohol dependence in mice and demonstrated that genetic ablation of IL-17 receptor A (IL-17ra(–/–)) or pharmacological blockade of IL-17 signaling effectively suppressed the increased voluntary alcohol drinking in alcohol-dependent mice and blocked alcohol-induced hepatocellular and neurological damage. The level of circulating IL-17A positively correlated with the alcohol use in excessive drinkers and was further increased in patients with ALD as compared with healthy individuals. Our data suggest that IL-17A is a common mediator of excessive alcohol consumption and alcohol-induced liver/brain injury, and targeting IL-17A may provide a novel strategy for treatment of alcohol-induced pathology.

Background & Aims Chronic liver injury often results in the activation of hepatic myofibroblasts and the development of liver fibrosis. Hepatic myofibroblasts may originate from 3 major sources: hepatic stellate cells (HSCs), portal fibroblasts (PFs), and fibrocytes, with varying contributions depending on the etiology of liver injury. Here, we assessed the composition of hepatic myofibroblasts in multidrug resistance gene 2 knockout (Mdr2−/−) mice, a genetic model that resembles primary sclerosing cholangitis in patients. Methods Mdr2−/− mice expressing a collagen-GFP reporter were analyzed at different ages. Hepatic non-parenchymal cells isolated from collagen-GFP Mdr2−/− mice were sorted based on collagen-GFP and vitamin A. An NADPH oxidase (NOX) 1/4 inhibitor was administrated to Mdr2−/− mice aged 12–16 weeks old to assess the therapeutic approach of targeting oxidative stress in cholestatic injury. Results Thy1+ activated PFs accounted for 26%, 51%, and 54% of collagen-GFP+ myofibroblasts in Mdr2−/− mice at 4, 8, and 16 weeks of age, respectively. The remaining collagen-GFP+ myofibroblasts were composed of activated HSCs, suggesting that PFs and HSCs are both activated in Mdr2−/− mice. Bone-marrow-derived fibrocytes minimally contributed to liver fibrosis in Mdr2−/− mice. The development of cholestatic liver fibrosis in Mdr2−/− mice was associated with early recruitment of Gr1+ myeloid cells and upregulation of pro-inflammatory cytokines (4 weeks). Administration of a NOX inhibitor to 12-week-old Mdr2−/− mice suppressed the activation of myofibroblasts and attenuated the development of cholestatic fibrosis. Conclusions Activated PFs and activated HSCs contribute to cholestatic fibrosis in Mdr2−/− mice, and serve as targets for antifibrotic therapy. Lay summary Activated portal fibroblasts and hepatic stellate cells, but not fibrocytes, contributed to the production of the fibrous scar in livers of Mdr2−/− mice, and these cells can serve as targets for antifibrotic therapy in cholestatic injury. Therapeutic inhibition of the enzyme NADPH oxidase (NOX) in Mdr2−/− mice reversed cholestatic fibrosis, suggesting that targeting NOXs may be an effective strategy for the treatment of cholestatic fibrosis.

The twin-arginine translocation (Tat) system transports folded proteins across bacterial and plant thylakoid membranes. Most current models for the translocation mechanism propose the coalescence of a substrate-binding TatABC complex with a separate TatA complex. In Escherichia coli, TatA complexes are widely believed to form the translocation pore, and the size variation of TatA has been linked to the transport of differently sized substrates. Here, we show that the TatA paralog TatE can substitute for TatA and support translocation of Tat substrates including AmiA, AmiC, and TorA. However, TatE is found as much smaller, discrete complexes. Gel filtration and blue native electrophoresis suggest sizes between ∼50 and 110 kDa, and single-particle processing of electron micrographs gives size estimates of 70-90 kDa. Three-dimensional models of the two principal TatE complexes show estimated diameters of 6-8 nm and potential clefts or channels of up to 2.5 nm diameter. The ability of TatE to support translocation of the 90-kDa TorA protein suggests alternative translocation models in which single TatA/E complexes do not contribute the bulk of the translocation channel. The homogeneity of both the TatABC and the TatE complexes further suggests that a discrete Tat translocase can translocate a variety of substrates, presumably through the use of a flexible channel. The presence and possible significance of double- or triple-ring TatE forms is discussed.

The biogenesis of the plant thylakoid network is an enormously complex process in terms of protein targeting. The membrane system contains a large number of proteins, some of which are synthesized within the organelle, while many others are imported from the cytosol. Studies in recent years have shown that the targeting of imported proteins into and across the thylakoid membrane is particularly complex, with four different targeting pathways identified to date. Two of these are used to target membrane proteins: a signal recognition particle (SRP)-dependent pathway and a highly unusual pathway that appears to require none of the known targeting apparatus. Two further pathways are used to translocate lumenal proteins across the thylakoid membrane from the stroma and, again, the two pathways differ dramatically from each other. One is a Sec-type pathway, in which ATP hydrolysis by SecA drives the transport of the substrate protein through the membrane in an unfolded conformation. The other is the twin-arginine translocation (Tat) pathway, where substrate proteins are transported in a folded state using a unique mechanism that harnesses the proton motive force across the thylakoid membrane. This article reviews progress in studies on the targeting of lumenal proteins, with reference to the mechanisms involved, their evolution from endosymbiotic progenitors of the chloroplast, and possible elements of regulation.

Muscular dystrophies are a group of hereditary disorders caused by mutations in genes that have essential roles in muscle function and are generally characterized by progressive muscle weakness and degeneration. Among those, Duchenne muscular dystrophy (DMD) is the most common and severe. DMD is a fatal, X-linked recessive disorder which affects 1 in 3500 boys and is caused by mutations in the dystrophin gene. Currently there is no cure for the disorder and treatment options are limited to physiotherapy and corticosteroids that slow the course of the disorder, but are also associated with severe side effects when administered over prolonged periods of time. This chapter will provide an overview of the approaches currently being pursued for the treatment of DMD and the state of the art strategies that are in clinical trials. Emphasis will be placed on describing the progress made over the years to reach the current state, as well as the challenges that the field of gene and molecular therapies face to ensure that the approach is safe to use in patients and effective.

Two independent twin-arginine translocases (Tat) for protein secretion were previously identified in the Gram-positive bacterium Bacillus subtilis . These consist of the TatAd-TatCd and TatAy-TatCy subunits. The function of a third TatA subunit named TatAc was unknown. Here, we show that TatAc can form active protein translocases with TatCd and TatCy.