S-nitroso-N-acetylcysteine attenuates liver fibrosis in cirrhotic rats

Phosphodiesterase Type 5 Inhibitors and Selective Estrogen Receptor Modulators Can Prevent But Not Reverse Myofibroblast Transformation in Peyronie's Disease

BACKGROUND

Myofibroblast transformation is a key step in the pathogenesis of Peyronie's disease (PD). Phosphodiesterase type 5 inhibitors (PDE5is) and selective estrogen receptor modulators (SERMs) can prevent the formation of fibrosis in in vitro and in vivo models of PD. However, it is unknown whether these drugs can also reverse established fibrosis.

AIM

To investigate whether PDE5is and SERMs can reverse transforming growth factor beta 1 (TGF-β1)-induced myofibroblast transformation and determine the point of no return.

METHODS

In-Cell enzyme-linked immunosorbent assay was used to quantify TGF-β1-induced myofibroblast transformation of human primary fibroblasts isolated from tunica albuginea (TA) of patients undergoing surgery for treatment of PD. Extracellular matrix production and collagen contraction assays were used as secondary assays. Reverse transcription-quantitative polymerase chain reaction and In-Cell enzyme-linked immunosorbent assay were used to measure drug target expression. PDE5i (vardenafil) and SERM (tamoxifen) were applied at various time points after TGF-β1.

OUTCOMES

Reversibility of myofibroblast transformation and drug target expression were investigated in a time-dependent manner in TA-derived fibroblasts.

RESULTS

Vardenafil or tamoxifen could not reverse the myofibroblast traits of alpha-smooth muscle actin expression and extracellular matrix production, whereas only tamoxifen affected collagen contraction after 72 hours of TGF-β1 treatment. Phosphodiesterase 5A and estrogen receptor (ER)-β were downregulated after 72 hours, and estrogen receptor -α protein could not be quantified. Tamoxifen could prevent myofibroblast transformation until 36 hours after TGF-β1 treatment, whereas vardenafil could prevent only 24 hours after TGF-β1 treatment. This was mirrored by downregulation of drug targets on mRNA and protein level. Furthermore, antifibrotic signaling pathways, peroxisome proliferator-activated receptor gamma and betaglycan (TGFB receptor III), were significantly downregulated after 36 hours of TGF-β1 exposure, as opposed to upregulation of profibrotic thrombospondin-1 at the same time point.

CLINICAL TRANSLATION

This study suggests that using PDE5is and SERMs might only help for early-phase PD and further highlights the need to test drugs at the appropriate stage of the disease based on their mechanism of action.

STRENGTHS & LIMITATIONS

The study uses primary human TA-derived fibroblasts that enhances translatability of the results. Limitations include that only 1 example of PDE5i- and SERM-type drug was tested. Time course experiments were only performed for marker expression experiments and not for functional assays.

CONCLUSION

This is the first study to demonstrate that timing for administration of drugs affecting myofibroblast transformation appears to be vital in in vitro models of PD, where 36 hours of TGF-β1 treatment can be suggested as a "point of no return" for myofibroblast transformation. Ilg MM, Stafford SJ, Mateus M, et al. Phosphodiesterase Type 5 Inhibitors and Selective Estrogen Receptor Modulators Can Prevent But Not Reverse Myofibroblast Transformation in Peyronie's Disease. J Sex Med 2020;17:1848-1864.

Antifibrotic effects of bezafibrate and pioglitazone against thioacetamide-induced liver fibrosis in albino rats

Activation of hepatic stellate cells is a central event in hepatic fibrogenesis that offers multiple potential sites for therapeutic interventions. Peroxisome proliferator-activated receptors are implicated in liver fibrosis. We aimed to evaluate the effect of bezafibrate and pioglitazone on a thioacetamide (TAA) rat model of liver fibrosis and to clarify the possible underlying mechanisms. Rats received intraperitoneal injections of TAA for 6 weeks. Daily oral treatments with bezafibrate or pioglitazone were started with the first day of TAA intoxication. Serum liver function tests, hepatic malondialdehyde (MDA), total nitrite and nitrate (NOx), superoxide dismutase, and hepatic histopathology were assessed to evaluate hepatic damage. Alpha smooth muscle actin (α-SMA) and tissue inhibitor metalloproteinase-1 (TIMP-1) and caspase-3 were also assessed. The TAA group experienced significant deterioration of liver functions, increased oxidative stress, and increased liver tissue NOx. Administration of bezafibrate or pioglitazone resulted in significant improvement of all liver functions and reduced oxidative stress in hepatic tissues. Only administration of bezafibrate significantly reduced NOx levels. Liver tissues from the TAA-treated group showed disrupted normal architecture. Administration of bezafibrate or pioglitazone attenuated this picture. Stronger α-SMA expression was detected in the TAA group. Treatment with bezafibrate or pioglitazone decreased the α-SMA expression.

Hepatoprotective Effect of Jianpi Huoxue Formula on Nonalcoholic Fatty Liver Disease Induced by Methionine-Choline-Deficient Diet in Rat

In parallel with the prevalence metabolic syndrome, nonalcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease in most countries. It features a constellation of simple steatosis, nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and even hepatocellular carcinoma. There are no approved drugs for effective management of NAFLD and NASH. Jianpi Huoxue formula (JPHX) mainly consists of Atractylodes macrocephal (Baizhu), Salvia miltiorrhiza (Danshen), Rasux Paeonia Alba (Baishao), Rhizoma Alismatis (Zexie), and Fructus Schisandrae Chinensis (Wuweizi), which may have beneficial effects on NAFLD. The aim of the study was to identify the effect of JPHX on NAFLD. A NAFLD model was induced by methionine-choline-deficient food (MCD) in Wistar rats and orally administered with simultaneous JPHX, once a day for 8 weeks. Hepatocellular injury, lipid profile, inflammation, fibrosis, and apoptosis were evaluated. The results showed that JPHX significantly decreased the abnormal serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels compared with the MCD model (P<0.05). Furthermore, JPHX protected MCD diet-fed rats from accumulation of hepatic triglycerides (TG) and total cholesterol (TC). Histological examination demonstrated that JPHX noticeably normalized the NAFLD activity score (NAS). Moreover, JPHX ameliorated liver inflammation by decreasing TNF-α levels and reduced collagen and matrix metalloproteinases in MCD diet-fed rats. In addition, JPHX prevented rats from MCD-induced cellular apoptosis, as suggested by TUNEL staining, and suppressed the activation of caspase 3 and 7 proteins. JPHX also inhibited the phosphorylation of JNK. In conclusion, JPHX exhibited a hepatoprotective effect against NAFLD in an MCD experimental model.

Long-term decomposition of aqueous S-nitrosoglutathione and S-nitroso-N-acetylcysteine: Influence of concentration, temperature, pH and light

Primary S-nitrosothiols (RSNOs) have received significant attention for their ability to modulate NO signaling in many physiological and pathophysiological processes. Such actions and their potential pharmaceutical uses demand a better knowledge of their stability in aqueous solutions. Herein, we investigated the effects of concentration, temperature, pH, room light and metal ions on the long-term kinetic behavior of two representative primary RSNOs, S-nitrosoglutathione (GSNO) and S-nitroso-N-acetylcysteine (SNAC). The thermal decomposition of GSNO and SNAC were shown to be affected by the auto-catalytic action of the thiyl radicals. At 25 °C in the dark and protected from the catalytic action of metal ions, GSNO and SNAC solutions 1 mM showed half-lives of 49 and 76 days, and apparent activation energies of 84 ± 14 and 90 ± 6 kJ mol^-1, respectively. Both GSNO and SNAC exhibited increased stability in the pH range 5-7. At high pH the decomposition pathway of GSNO involves the formation of an intermediate (GS-NO₂^2-), which decomposes generating GSH and nitrite. GSNO solutions displayed lower sensitivity to the catalytic action of metal ions than SNAC and the exposure to room light led to a 5-fold increase in the initial rates of decomposition of both RSNOs. In all comparisons, SNAC solutions showed higher stability than GSNO solutions. These findings provide strategic information about the stability of GSNO and SNAC and may open new perspectives for their use as experimental or therapeutic NO donors.

Sphingosine 1-Phosphate Signaling as a Target in Hepatic Fibrosis Therapy

Liver fibrosis is an excess production of extracellular matrix proteins as a result of chronic liver disease which leads to cell death and organ dysfunction. The key cells involved in fibrogenesis are resident hepatic stellate cells (HSCs) which are termed myofibroblasts after activation, acquiring contractile, proliferative, migratory and secretory capability. Sphingosine 1-phosphate (S1P) is a bioactive sphingolipid with well-established effects on angiogenesis, carcinogenesis and immunity. Accumulating evidence demonstrates that this metabolite is involved in the profibrotic inflammatory process through the regulation of pleiotropic cell responses, such as vascular permeability, leukocyte infiltration, cell survival, migration, proliferation and HSCs differentiation to myofibroblasts. S1P is synthesized by sphingosine kinases (SphKs) and many of its actions are mediated by S1P specific cell surface receptors (S1P_1-5), although different intracellular targets of S1P have been identified. Modulation of SphKs/S1P/S1P receptors signaling is known to result in beneficial effects on various in vivo and in vitro models of liver fibrosis. Thus, a better knowledge of the molecular mechanisms involved in the modulation of the S1P pathway could help to improve liver fibrosis therapy. In this review, we analyze the effects of the S1P axis on the fibrogenic process, and the involvement of a range of inhibitors or approaches targeting enzymes related to S1P in the abrogation of pathological fibrogenesis. All in all, targeting this pathway offers therapeutic potential in the treatment of hepatic fibrosis.

Metabolic Profile Changes of CCl₄-Liver Fibrosis and Inhibitory Effects of Jiaqi Ganxian Granule

Jiaqi Ganxian Granule (JGG) is a famous traditional Chinese medicine, which has been long used in clinical practice for treating liver fibrosis. However, the mechanism underlying its anti-hepatic fibrosis is still not clear. In this study, an Ultra-Performance Liquid Chromatography-Time-Of-Flight Mass Spectrometry (UPLC-TOF-MS)-based metabolomics strategy was used to profile the metabolic characteristic of serum obtained from a carbon tetrachloride (CCl₄)-induced hepatic fibrosis model in Sprague-Dawley (SD) rats with JGG treatment. Through Principal Component Analysis (PCA) and Partial Least Square Discriminant Analysis (PLS-DA), it was shown that metabolic perturbations induced by CCl₄ were inhibited after treatment of JGG, for 17 different metabolites related to CCl₄. Among these compounds, the change tendency of eight potential drug targets was restored after the intervention with JGG. The current study indicates that JGG has a significant anti-fibrosis effect on CCl₄-induced liver fibrosis in rats, which might be by regulating the dysfunction of sphingolipid metabolism, glycerophospholipid metabolism, N-acylethanolamine biosynthesis, fat digestion and absorption, while glycerophospholipid metabolism played vital roles in the inhibitory effects of JGG on hepatic fibrosis according to Metabolic Pathway Analysis (MetPA). Our findings indicated that the metabolomics approach may provide a useful tool for exploring potential biomarkers involved in hepatic fibrosis and elucidate the mechanisms underlying the action of therapies used in traditional Chinese medicine.

Activators and stimulators of soluble guanylate cyclase counteract myofibroblast differentiation of prostatic and dermal stromal cells

BACKGROUND

Fibrotic diseases encompass numerous systemic and organ-specific disorders characterized by the development and persistence of myofibroblasts. TGFβ1 is considered the key inducer of fibrosis and drives myofibroblast differentiation in cells of diverse histological origin by a pro-oxidant shift in redox homeostasis associated with decreased nitric oxide (NO)/cGMP signaling. Thus, enhancement of NO/cGMP represents a potential therapeutic strategy to target myofibroblast activation and therefore fibrosis.

METHODS

Myofibroblast differentiation was induced by TGFβ1 in human primary prostatic (PrSCs) and normal dermal stromal cells (NDSCs) and monitored by α smooth muscle cell actin (SMA) and IGF binding protein 3 (IGFBP3) mRNA and protein levels. The potential of enhanced cGMP production by the sGC stimulator BAY 41-2272 or the sGC activator BAY 60-2770 to inhibit and revert myofibroblast differentiation in vitro was analyzed. Moreover, potential synergisms of BAY 41-2272 or BAY 60-2770 and inhibition of cGMP degradation by the PDE5 inhibitor vardenafil were investigated.

RESULTS

BAY 41-2272 and BAY 60-2770 at doses of 30µM significantly inhibited induction of SMA and IGFBP3 levels in PrSCs and reduced myofibroblast marker levels in TGFβ1-predifferentiated cells. At lower concentrations (3 and 10µM) only BAY 41-2272 but not BAY 60-2770 significantly inhibited and reverted myofibroblast differentiation. In NDSCs both substances significantly inhibited differentiation at all concentrations tested. Attenuation of SMA expression was more pronounced in NDSCs whereas reduction of IGFBP3 levels by BAY 41-2272 appeared more efficient in PrSCs. Moreover, administration of BAY 41-2272 or BAY 60-2770 enhanced the efficiency of the PDE5 inhibitor vardenafil to inhibit and revert myofibroblast differentiation in vitro.

CONCLUSIONS

Increase of cGMP by sGC stimulation/activation significantly inhibited and reverted myofibroblast differentiation. This effect was even more pronounced when a combination treatment with a PDE5 inhibitor was applied. Thus, enhancement of NO/cGMP-signaling by sGC stimulation/activation is a promising strategy for the treatment of fibrotic diseases. Whereas, in NDSCs BAY 60-2770 and BAY 41-2272 exerted similar effects on myofibroblast differentiation, higher potency of BAY 41-2272 was observed in PrSCs, indicating phenotypical differences between fibroblasts form different organs that should be taken into account in the search for antifibrotic therapies.

Adiponectin attenuates liver fibrosis by inducing nitric oxide production of hepatic stellate cells

Adiponectin protects against liver fibrosis, but the mechanisms have not been fully elucidated. Here, we showed that adiponectin upregulated inducible nitric oxide synthase (iNOS) messenger RNA (mRNA) and protein expression in hepatic non-parenchymal cells, particularly in hepatic stellate cells (HSCs), and increased nitric oxide (NO2-/NO3-) concentration in HSC-conditioned medium. Adiponectin attenuated HSC proliferation and migration but promoted apoptosis in a NO-dependent manner. More advanced liver fibrosis with decreased iNOS/NO levels was observed in adiponectin knockout mice comparing to wide-type mice when administered with CCI4 while NO donor supplementation rescued the phenotype. Further experiments demonstrated that adiponectin-induced iNOS/NO system activation is mediated through adipoR2-AMPK-JNK/Erk1/2-NF-κB signaling. These data suggest that adiponectin inhibits HSC function, further limiting the development of liver fibrosis at least in part through adiponectin-induced NO release. Therefore, adiponectin-mediated NO signaling may be a novel target for the treatment of liver fibrosis.

KEY MESSAGES

• Adiponectin activates HSC iNOS/NO and SEC eNOS/NO systems. • Adiponectin inhibits HSC proliferation and migration but promotes its apoptosis. • Adiponectin inhibits CCL4-induced liver fibrosis by modulation of liver iNOS/NO. • Adiponectin stimulates HSC iNOS/NO via adipoR2-AMPK-JNK/ErK1/2-NF-κB pathway.

The use of nanoparticles to deliver nitric oxide to hepatic stellate cells for treating liver fibrosis and portal hypertension

Polymeric nanoparticles are designed to transport and deliver nitric oxide (NO) into hepatic stellate cells (HSCs) for the potential treatment of both liver fibrosis and portal hypertension. The nanoparticles, incorporating NO donor molecules (S-nitrosoglutathione compound), are designed for liver delivery, minimizing systemic delivery of NO. The nanoparticles are decorated with vitamin A to specifically target HSCs. We demonstrate, using in vitro and in vivo experiments, that the targeted nanoparticles are taken up specifically by rat primary HSCs and the human HSC cell line accumulating in the liver. When nanoparticles, coated with vitamin A, release NO in liver cells, we find inhibition of collagen I and α-smooth muscle actin (α-SMA), fibrogenic genes associated with activated HSCs expression in primary rat liver and human activated HSCs without any obvious cytotoxic effects. Finally, NO-releasing nanoparticles targeted with vitamin A not only attenuate endothelin-1 (ET-1) which elicites HSC contraction but also acutely alleviates haemodynamic disorders in bile duct-ligated-induced portal hypertension evidenced by decreasing portal pressure (≈20%) and unchanging mean arterial pressure. This study clearly shows, for the first time, the potential for HSC targeted nanoparticle delivery of NO as a treatment for liver diseases with proven efficacy for alleviating both liver fibrosis and portal hypertension.

Nitric oxide released from luminal s-nitroso-N-acetylcysteine increases gastric mucosal blood flow

Nitric oxide (NO)-mediated vasodilation plays a key role in gastric mucosal defense, and NO-donor drugs may protect against diseases associated with gastric mucosal blood flow (GMBF) deficiencies. In this study, we used the ex vivo gastric chamber method and Laser Doppler Flowmetry to characterize the effects of luminal aqueous NO-donor drug S-nitroso-N-acetylcysteine (SNAC) solution administration compared to aqueous NaNO2 and NaNO3 solutions (pH 7.4) on GMBF in Sprague-Dawley rats. SNAC solutions (600 μM and 12 mM) led to a rapid threefold increase in GMBF, which was maintained during the incubation of the solutions with the gastric mucosa, while NaNO2 or NaNO3 solutions (12 mM) did not affect GMBF. SNAC solutions (600 μM and 12 mM) spontaneously released NO at 37 °C at a constant rate of 0.3 or 14 nmol·mL-1·min-1, respectively, while NaNO2 (12 mM) released NO at a rate of 0.06 nmol·mL-1·min-1 and NaNO3 (12 mM) did not release NO. These results suggest that the SNAC-induced GMBF increase is due to their higher rates of spontaneous NO release compared to equimolar NaNO2 solutions. Taken together, our data indicate that oral SNAC administration is a potential approach for gastric acid-peptic disorder prevention and treatment.

Melatonin limits the expression of profibrogenic genes and ameliorates the progression of hepatic fibrosis in mice

We investigated whether melatonin ameliorates fibrosis and limits the expression of fibrogenic genes in mice treated with carbon tetrachloride (CCl4). Mice in treatment groups received CCl4 5 μL/g body weight intraperitoneally twice a week for 4 or 6 weeks. Melatonin was given at 5 or 10 mg/kg/d intraperitoneally, beginning 2 weeks after the start of CCl4 administration. Treatment with CCl4 resulted in fibrosis evidenced by the staining of Van Gieson and α-smooth muscle actin (α-SMA) positive cells in the liver. At both 4 and 6 weeks, CCl4 induced an increase in the messenger RNA levels of collagens I and III, transforming growth factor (TGF)-β, platelet-derived growth factor (PDGF), connective tissue growth factor (CTGF), amphiregulin, matrix metalloproteinase (MMP)-9, and tissue inhibitor of metalloproteinase (TIMP)-1. Protein concentrations of CTGF, amphiregulin, MMP-9, TIMP-1, and phospho-Smad3 were also significantly augmented in fibrotic mice. Melatonin successfully attenuated liver injury, as shown by histopathology and decreased levels of serum transaminases. Immunohistochemical staining of α-SMA indicated an abrogation of hepatic stellate cell activation by the indol. Furthermore, melatonin treatment resulted in significant inhibition of the expression of collagens I and III, TGF-β, PDGF, CTGF, amphiregulin, and phospho-Smad3. The MMP-9 activity decreased and the expression of nuclear factor erythroid-2-related factor 2 (Nrf2) increased in mice receiving melatonin. Data obtained suggest that attenuation of multiple profibrogenic gene pathways contributes to the beneficial effects of melatonin in mice with CCl4-induced liver fibrosis.

Nonalcoholic Fatty liver disease: pathogenesis and therapeutics from a mitochondria-centric perspective

Nonalcoholic fatty liver disease (NAFLD) describes a spectrum of disorders characterized by the accumulation of triglycerides within the liver. The global prevalence of NAFLD has been increasing as the obesity epidemic shows no sign of relenting. Mitochondria play a central role in hepatic lipid metabolism and also are affected by upstream signaling pathways involved in hepatic metabolism. This review will focus on the role of mitochondria in the pathophysiology of NAFLD and touch on some of the therapeutic approaches targeting mitochondria as well as metabolically important signaling pathways. Mitochondria are able to adapt to lipid accumulation in hepatocytes by increasing rates of beta-oxidation; however increased substrate delivery to the mitochondrial electron transport chain (ETC) leads to increased reactive oxygen species (ROS) production and eventually ETC dysfunction. Decreased ETC function combined with increased rates of fatty acid beta-oxidation leads to the accumulation of incomplete products of beta-oxidation, which combined with increased levels of ROS contribute to insulin resistance. Several related signaling pathways, nuclear receptors, and transcription factors also regulate hepatic lipid metabolism, many of which are redox sensitive and regulated by ROS.

Reversal of myofibroblast differentiation: a review

It has long been considered that fibrosis and fibroblast-to-myofibroblast differentiation are irreversible processes. However, recent data obtained indicates that tissue fibrosis and fibroblast-to-myofibroblast differentiation can indeed be reversed, which offers the possibility of a new therapeutic approach for fibrotic disorders. Here, we discuss the origin of the myofibroblasts and different aspects of their differentiation, especially the key mediators and TGFβ-induced signaling pathways. We also report here a few factors involved in myofiroblast dedifferentiation and several compounds which can reverse the established dedifferentiated myofibroblast, as examples that provide the reader a glimpse of the current trends of approach for discovering useful anti-fibrotic drugs.

Hepatic inflammation and progressive liver fibrosis in chronic liver disease

Chronic liver inflammation drives hepatic fibrosis, and current immunosuppressive, anti-inflammatory, and anti-viral therapies can weaken this driver. Hepatic fibrosis is reversed, stabilized, or prevented in 57%-79% of patients by conventional treatment regimens, mainly by their anti-inflammatory actions. Responses, however, are commonly incomplete and inconsistently achieved. The fibrotic mechanisms associated with liver inflammation have been clarified, and anti-fibrotic agents promise to improve outcomes as adjunctive therapies. Hepatitis C virus and immune-mediated responses can activate hepatic stellate cells by increasing oxidative stress within hepatocytes. Angiotensin can be synthesized by activated hepatic stellate cells and promote the production of reactive oxygen species. Anti-oxidants (N-acetylcysteine, S-adenosyl-L-methionine, and vitamin E) and angiotensin inhibitors (losartin) have had anti-fibrotic actions in preliminary human studies, and they may emerge as supplemental therapies. Anti-fibrotic agents presage a new era of supplemental treatment for chronic liver disease.

Redox signaling as a therapeutic target to inhibit myofibroblast activation in degenerative fibrotic disease

Degenerative fibrotic diseases encompass numerous systemic and organ-specific disorders. Despite their associated significant morbidity and mortality, there is currently no effective antifibrotic treatment. Fibrosis is characterized by the development and persistence of myofibroblasts, whose unregulated deposition of extracellular matrix components disrupts signaling cascades and normal tissue architecture leading to organ failure and death. The profibrotic cytokine transforming growth factor beta (TGFβ) is considered the foremost inducer of fibrosis, driving myofibroblast differentiation in diverse tissues. This review summarizes recent in vitro and in vivo data demonstrating that TGF β-induced myofibroblast differentiation is driven by a prooxidant shift in redox homeostasis. Elevated NADPH oxidase 4 (NOX4)-derived hydrogen peroxide (H2O2) supported by concomitant decreases in nitric oxide (NO) signaling and reactive oxygen species scavengers are central factors in the molecular pathogenesis of fibrosis in numerous tissues and organs. Moreover, complex interplay between NOX4-derived H2O2 and NO signaling regulates myofibroblast differentiation. Restoring redox homeostasis via antioxidants or NOX4 inactivation as well as by enhancing NO signaling via activation of soluble guanylyl cyclases or inhibition of phosphodiesterases can inhibit and reverse myofibroblast differentiation. Thus, dysregulated redox signaling represents a potential therapeutic target for the treatment of wide variety of different degenerative fibrotic disorders.

Review article: The prevention and reversal of hepatic fibrosis in autoimmune hepatitis

BACKGROUND

Immunosuppressive treatment of autoimmune hepatitis can prevent or reverse hepatic fibrosis, but these anti-fibrotic effects are inconsistent secondary gains.

AIM

To describe the anti-fibrotic effects of current therapies for autoimmune hepatitis, discuss the pathogenic mechanisms of hepatic fibrosis that might be targeted by anti-fibrotic interventions, indicate the non-invasive diagnostic tests of hepatic fibrosis that must be validated in autoimmune hepatitis and to suggest promising treatment opportunities.

METHODS

Studies cited in PubMed from 1972 to 2013 for autoimmune hepatitis, hepatic fibrosis, cirrhosis, anti-fibrotic therapy and non-invasive tests of hepatic fibrosis were selected.

RESULTS

Hepatic fibrosis improves in 53-57% of corticosteroid-treated patients with autoimmune hepatitis; progressive fibrosis slows or is prevented in 79%; and cirrhosis may be reversed. Progressive hepatic fibrosis is associated with liver inflammation, and the inability to fully suppress inflammatory activity within 12 months is associated with progression to cirrhosis (54%) and death or need for liver transplantation (15%). Liver tissue examination remains the gold standard for assessing hepatic fibrosis, but laboratory and radiological tests may be useful non-invasive methods to measure the fibrotic response. Severe liver inflammation can confound radiological assessments, and the preferred non-invasive test in autoimmune hepatitis is uncertain. Individualised treatment adjustments and adjunctive anti-fibrotic therapies are poised for study in this disease.

CONCLUSIONS

The prevention and reversal of hepatic fibrosis are achievable objectives in autoimmune hepatitis. Strategies that evaluate individualised therapies adjusted to the rapidity and completeness of the inflammatory response, and the use of adjunctive anti-fibrotic interventions, must be evaluated.

Serum levels and polymorphisms of matrix metalloproteinases (MMPs) in carotid artery atherosclerosis: higher MMP-9 levels are associated with plaque vulnerability

CONTEXT

Matrix metalloproteinases are involved in atherosclerosis and plaque vulnerability.

OBJECTIVE

To investigate serum levels and genetic polymorphisms of matrix metalloproteinases (MMPs) -1, -3 and -9 in patients submitted to carotid endarterectomy.

METHODS

Genetic polymorphisms were evaluated using polymerase chain reaction (PCR-RFLP); serum levels were measured using ELISA; histological sections were stained with Picrosirius Red to analyze the fibrous cap thickness, lipid core and collagen content and with hematoxylin--eosin to detect the presence of intraplaque hemorrhage.

RESULTS

MMP-9 serum levels were significantly higher in patients with a thinner fibrous cap (p = 0.033) or acute or recent intraplaque hemorrhage (p = 0.008) on histology, as well as in patients with previous stroke (p = 0.009) or peripheral vascular disease (p = 0.049). No consistent associations were observed between different MMP genotypes and fibrous cap thickness, lipid core, collagen content or intraplaque hemorrhage.

CONCLUSIONS

MMP-9 serum levels were consistently associated with markers of carotid atherosclerosis and lesion vulnerability, whereas specific MMP genotypes were not.

S-nitroso-N-acetylcysteine attenuates liver fibrosis in experimental nonalcoholic steatohepatitis

S-Nitroso-N-acetylcysteine (SNAC) is a water soluble primary S-nitrosothiol capable of transferring and releasing nitric oxide and inducing several biochemical activities, including modulation of hepatic stellate cell activation. In this study, we evaluated the antifibrotic activity of SNAC in an animal model of nonalcoholic steatohepatitis (NASH) induced in Sprague-Dawley rats fed with a choline-deficient, high trans fat diet and exposed to diethylnitrosamine for 8 weeks. The rats were divided into three groups: SNAC, which received oral SNAC solution daily; NASH, which received the vehicle; and control, which received standard diet and vehicle. Genes related to fibrosis (matrix metalloproteinases [MMP]-13, -9, and -2), transforming growth factor β-1 [TGFβ-1], collagen-1α, and tissue inhibitors of metalloproteinase [TIMP-1 and -2] and oxidative stress (heat-shock proteins [HSP]-60 and -90) were evaluated. SNAC led to a 34.4% reduction in the collagen occupied area associated with upregulation of MMP-13 and -9 and downregulation of HSP-60, TIMP-2, TGFβ-1, and collagen-1α. These results indicate that oral SNAC administration may represent a potential antifibrotic treatment for NASH.

N-acetylcysteine improves antitumoural response of Interferon alpha by NF-kB downregulation in liver cancer cells

Background

Liver cancer is one of the most common malignancies in the world and at the moment, there is no drug intervention effective for the treatment of liver tumours. Investigate the effect of N-acetylcysteine (NAC), which has been studied for its antitumoural properties, on the toxicity of hepatocarcinoma (HCC) cells in vitro when used with the drug interferon alpha-2A (IFN), which is used clinically to treat HCC.

Results

NAC, IFN and NAC plus IFN reduced cell viability, as determined by MTT assay. More importantly, NAC potentiates the cytotoxic effect of IFN, with the best response achieved with 10 mM of NAC and 2.5 x 10⁴ of IFN. These results were confirmed by Annexin/PI staining through flow cytometry and morphologic analyses. Co-treatment reduced the expression of the nuclear transcription factor kappa-B (NF-kB). In a similar way to NAC, RNAi against p65 potentiated the toxic effect of IFN, suggesting that, indeed, NAC may be enhancing the effect of IFN through inhibition of NF-kB.

Conclusions

Our results support the notion that NAC may be an important drug for the treatment of liver tumours as primary or adjuvant therapy. IFN has a limited clinical response, and therefore, the anti-proliferative properties of NAC in the liver should be explored further as an alternative for non-responders to IFN treatment.

N-acetylcysteine for the prevention of stricture after circumferential endoscopic submucosal dissection of the esophagus: a randomized trial in a porcine model

Background

Circumferential endoscopic submucosal dissection (CESD) of the esophagus would allow for both the eradication of Barrett’s esophagus and its related complications, such as advanced neoplasia. However, such procedures generally induce inflammatory repair resulting in a fibrotic stricture. N-acetylcysteine (NAC) is an antioxidant that has shown some efficacy against pulmonary and hepatic fibrosis. The aim of our study was to evaluate the benefit of NAC in the prevention of esophageal cicatricial stricture after CESD in a swine model.

Animals and methods

Two groups of six pigs each were subjected to general anesthesia and CESD: after randomization, a first group received an oral NAC treatment regimen of 100 mg/kg/day, initiated one week before the procedure, whereas a second group was followed without any prophylactic treatment. Follow-up endoscopies took place seven, fourteen, twenty-one, and twenty-eight days after CESD. Necropsy, histological assessment of esophageal inflammation, and fibrosis were performed on day 28.

Results

The median esophageal lumen diameter on day 21 (main judgment criterion) was 4 mm (range 2 to 5) in group 1 and 3 mm (range 1 to 7) in group 2 (P = 0.95). No significant difference was observed between the two groups regarding clinical evaluation (time before onset of clinically significant esophageal obstruction), number of dilations, esophageal inflammation and fibrosis, or oxidative stress damage on immunohistochemistry.

Conclusions

Despite its antioxidant effect, systemic administration of NAC did not show significant benefit on esophageal fibrosis in our animal model of esophageal wound healing within the experimental conditions of this study. Since the administered doses were relatively high, it seems unlikely that NAC might be a valuable option for the prevention of post-endoscopic esophageal stricture.

Current status of novel antifibrotic therapies in patients with chronic liver disease

Fibrosis accumulation is a dynamic process resulting from a wound-healing response to acute or chronic liver injury of all causes. The cascade starts with hepatocyte necrosis and apoptosis, which instigate inflammatory signaling by chemokines and cytokines, recruitment of immune cell populations, and activation of fibrogenic cells, culminating in the deposition of extracellular matrix. These key elements, along with pathways of transcriptional and epigenetic regulation, represent fertile therapeutic targets. New therapies include drugs specifically designed as antifibrotics, as well as drugs already available with well-established safety profiles, whose mechanism of action may also be antifibrotic. At the same time, the development of noninvasive fibrogenic markers, and techniques (e.g. fibroscan), as well as combined scoring systems incorporating serum and clinical features will allow improved assessment of therapy response. In aggregate, the advances in the elucidation of the biology of fibrosis, combined with improved technologies for assessment will provide a comprehensive framework for design of antifibrotics and their analysis in well-designed clinical trials. These efforts may ultimately yield success in halting the progression of, or reversing, liver fibrosis.

Thymosin-β4 (Tβ4) blunts PDGF-dependent phosphorylation and binding of AKT to actin in hepatic stellate cells

Hepatic stellate cell transdifferentiation is a key event in the fibrogenic cascade. Therefore, attempts to prevent and/or revert the myofibroblastic phenotype could result in novel therapeutic approaches to treat liver cirrhosis. The expression of platelet-derived growth factor (PDGF)-β receptor and the proliferative response to platelet-derived growth factor-ββ (PDGF-ββ) are hallmarks of the transdifferentiation of hepatic stellate cells (HSC). In this communication, we investigated whether thymosin-β4 (Tβ4), a chemokine expressed by HSC could prevent PDGF-BB-mediated proliferation and migration of cultured HSC. Using early passages of human HSC, we showed that Tβ4 inhibited cell proliferation and migration and prevented the expression of PDGF-β receptor (PDGF-βr), α-smooth muscle actin and α1(I) collagen mRNAs. Tβ4 also inhibited the reappearance of PDGF-βr after its PDGF-BB-dependent degradation. These PDGF-dependent events were associated with the inhibition of AKT phosphorylation at both T308 and S473 amino acid residues. The lack of AKT phosphorylation was not due to the inhibition of PDGF-βr phosphorylation, the activation of phosphoinositide 3-kinase (PI3K), pyruvate dehydrogenase kinase isozyme 1 (PDK1), and mammalian target of rapamycin (mTOR). We found that PDGF-BB induced AKT binding to actin, and that Tβ4 prevented this effect. Tβ4 also prevented the activation of freshly isolated HSC cultured in the presence of Dulbecco's modified Eagle's medium or Dulbecco's minimal essential medium containing 10% fetal bovine serum. In conclusion, overall, our findings suggest that Tβ4 by sequestering actin prevents binding of AKT, thus inhibiting its phosphorylation. Therefore, Tβ4 has the potential to be an antifibrogenic agent.

S-Nitroso-N-acetylcysteine induces de-differentiation of activated hepatic stellate cells and promotes antifibrotic effects in vitro

Nitric oxide (NO) has been shown to act as a potent antifibrogenic agent by decreasing myofibroblast differentiation. S-Nitroso-N-acetylcysteine (SNAC), a NO donor, attenuates liver fibrosis in rats, but the cellular and molecular mechanisms on liver myofibroblast-like phenotype still remain unknown. Here, we investigate the antifibrotic effects of SNAC on hepatic stellate cells, the major fibrogenic cell type in the liver. A murine GRX cell line was incubated with SNAC (100μM) or vehicle (control group) for 72h. Cell viability was measured by MTT colorimetric assay and the conversion of myofibroblast into quiescent fat-storing cell phenotype was evaluated by Oil-Red-O staining. TGFβ-1, TIMP-1, and MMP-13 levels were measure in the supernatant by ELISA. Profibrogenic- and fibrolytic-related gene expression was quantified using real-time qPCR. SNAC induced phenotype conversion of myofibroblast-like phenotype into quiescent cells. SNAC decreased gene and protein expression of TGFβ-1 and MMP-2 compared to control groups. Besides, SNAC down-regulated profibrogenic molecules and up-regulated MMP-13 gene expression, which plays a key role in the degradation of interstitial collagen in liver fibrosis. In conclusion, these findings demonstrate that SNAC efficiently can modulate the activation and functionality of murine hepatic stellate cells and could be considered as an antifibrotic treatment to human liver fibrosis.

Molecular pathogenesis of hepatic fibrosis and current therapeutic approaches

The pathogenesis of hepatic fibrosis involves significant deposition of fibrilar collagen and other extracellular matrix proteins. It is a rather dynamic process of wound healing in response to a variety of persistent liver injury caused by factors such as ethanol intake, viral infection, drugs, toxins, cholestasis, and metabolic disorders. Liver fibrosis distorts the hepatic architecture, decreases the number of endothelial cell fenestrations and causes portal hypertension. Key events are the activation and transformation of quiescent hepatic stellate cells into myofibroblast-like cells with the subsequent up-regulation of proteins such as α-smooth muscle actin, interstitial collagens, matrix metalloproteinases, tissue inhibitor of metalloproteinases, and proteoglycans. Oxidative stress is a major contributing factor to the onset of liver fibrosis and it is typically associated with a decrease in the antioxidant defense. Currently, there is no effective therapy for advanced liver fibrosis. In its early stages, liver fibrosis is reversible upon cessation of the causative agent. In this review, we discuss some aspects on the etiology of liver fibrosis, the cells involved, the molecular pathogenesis, and the current therapeutic approaches.

Fabrication and characterization of an inorganic gold and silica nanoparticle mediated drug delivery system for nitric oxide

Nitric oxide (NO) plays an important role in inhibiting the development of hepatic fibrosis and its ensuing complication of portal hypertension by inhibiting human hepatic stellate cell (HSC) activation. Here we have developed a gold nanoparticle and silica nanoparticle mediated drug delivery system containing NO donors, which could be used for potential therapeutic application in chronic liver disease. The gold nanoconjugates were characterized using several physico-chemical techniques such as UV-visible spectroscopy and transmission electron microscopy. Silica nanoconjugates were synthesized and characterized as reported previously. NO released from gold and silica nanoconjugates was quantified under physiological conditions (pH = 7.4 at 37 degrees C) for a substantial period of time. HSC proliferation and the vascular tube formation ability, manifestations of their activation, were significantly attenuated by the NO released from these nanoconjugates. This study indicates that gold and silica nanoparticle mediated drug delivery systems for introducing NO could be used as a strategy for the treatment of hepatic fibrosis or chronic liver diseases, by limiting HSC activation.