Taurolithocholate impairs bile canalicular motility and canalicular bile secretion in isolated rat hepatocyte couplets

Secondary bile acids and the biliary epithelia: The good and the bad

The biliary tract has been considered for several decades a passive system just leading the hepatic bile to the intestine. Nowadays several researches demonstrated an important role of biliary epithelia (i.e. cholangiocytes) in bile formation. The study of biliary processes therefore maintains a continuous interest since the possible important implications regarding chronic cholestatic human diseases, such as primary biliary cholangitis or primary sclerosing cholangitis. Bile acids (BAs), produced by the liver, are the most represented organic molecules in bile. The physiologic importance of BAs was initially attributed to their behavior as natural detergents but several studies now demonstrate they are also important signaling molecules. In this minireview the effect of BAs on the biliary epithelia are reported focusing in particular on secondary (deriving by bacterial manipulation of primary molecules) ones. This class of BAs is demonstrated to have relevant biological effects, ranging from toxic to therapeutic ones. In this family ursodeoxycholic and lithocholic acid present the most interesting features. The molecular mechanisms linking ursodeoxycholic acid to its beneficial effects on the biliary tract are discussed in details as well as data on the processes leading to lithocholic damage. These findings suggest that expansion of research in the field of BAs/cholangiocytes interaction may increase our understanding of cholestatic diseases and should be helpful in designing more effective therapies for biliary disorders.

Curcumin Improves Chronic Pain Induced Depression Through Regulating Serum Metabolomics in a Rat Model of Trigeminal Neuralgia

Background

Depression is a prevalent and complex psychiatric disorder with high incidence in patients with chronic pain. The underlying pathogenesis of chronic pain-induced depression is complicated and remains largely unclear. An integrated analysis of endogenous substance-related metabolisms would help to understand the molecular mechanism of chronic pain-induced depression. Curcumin was reported to exert various health benefits, such as anti-depression, antioxidant, antineoplastic, analgesia, and anti-inflammation.

Objective

The aim of this study was to analyze the biomarkers related to depression in serum and to evaluate the anti-depression properties of curcumin in a chronic pain-induced depression model of rats.

Design

This is a randomized, controlled experiment.

Setting

This study was conducted at the Experimental Animal Center, Beijing Friendship Hospital, Capital Medical University.

Methods

Trigeminal neuralgia (TN) was produced by injecting 4 µL, 10% cobra venom saline solution into the infraorbital nerve (ION). Curcumin was administered by gavage twice a day from post-operation day (POD) 15 to POD 42. Mechanical allodynia was assessed using von Frey filaments. Sucrose preference and forced swimming tests were performed to evaluate depression-like behaviors. The metabolomics analysis was preceded by LCMS-IT-TOF and multivariate statistical methods for sample detection and biomarker screening.

Results

Cobra venom intra-ION injection led to chronic mechanical allodynia, reduced sucrose preference, and prolonged immobility during forced swimming. Curcumin treatment alleviated chronic mechanical allodynia, regained sucrose preference, and reduced immobility time. Differential analysis identified 30 potential metabolites changed under TN condition. The integrated analyses further revealed two major metabolic changes by comparing the serums from sham operated rats, TN rats, and TN rats treated with curcumin: 1) ether lipid metabolism; and 2) glycerophospholipid metabolism, and suggested that curcumin may improve chronic pain-induced depression by regulating these two types of lipid metabolisms.

Conclusion

Ether lipid and glycerophospholipid metabolism might be two of the pathways with the most potential related to chronic pain induced-depression; and curcumin could alleviate chronic pain induced-depression by modulating these two pathways. These results provide further insights into the mechanisms of chronic pain-induced depression and may help to identify potential targets for anti-depression properties of curcumin.

Bile canaliculi contract autonomously by releasing calcium into hepatocytes via mechanosensitive calcium channel

Drug-induced hepatocellular cholestasis leads to altered bile flow. Bile is propelled along the bile canaliculi (BC) by actomyosin contractility, triggered by increased intracellular calcium (Ca²⁺). However, the source of increased intracellular Ca²⁺ and its relationship to transporter activity remains elusive. We identify the source of the intracellular Ca²⁺ involved in triggering BC contractions, and we elucidate how biliary pressure regulates Ca²⁺ homeostasis and associated BC contractions. Primary rat hepatocytes were cultured in collagen sandwich. Intra-canalicular Ca²⁺ was measured with fluo-8; and intra-cellular Ca²⁺ was measured with GCaMP. Pharmacological modulators of canonical Ca²⁺-channels were used to study the Ca²⁺-mediated regulation of BC contraction. BC contraction correlates with cyclic transfer of Ca²⁺ from BC to adjacent hepatocytes, and not with endoplasmic reticulum Ca²⁺. A mechanosensitive Ca²⁺ channel (MCC), Piezo-1, is preferentially localized at BC membranes. The Piezo-1 inhibitor GsMTx-4 blocks the Ca²⁺ transfer, resulting in cholestatic generation of BC-derived vesicles whereas Piezo-1 hyper-activation by Yoda1 increases the frequency of Ca²⁺ transfer and BC contraction cycles. Yoda1 can recover normal BC contractility in drug-induced hepatocellular cholestasis, supporting that Piezo-1 regulates BC contraction cycles. Finally, we show that hyper-activating Piezo-1 can be exploited to normalize bile flow in drug-induced hepatocellular cholestasis.

Rho-kinase/myosin light chain kinase pathway plays a key role in the impairment of bile canaliculi dynamics induced by cholestatic drugs

Intrahepatic cholestasis represents a frequent manifestation of drug-induced liver injury; however, the mechanisms underlying such injuries are poorly understood. In this study of human HepaRG and primary hepatocytes, we found that bile canaliculi (BC) underwent spontaneous contractions, which are essential for bile acid (BA) efflux and require alternations in myosin light chain (MLC2) phosphorylation/dephosphorylation. Short exposure to 6 cholestatic compounds revealed that BC constriction and dilation were associated with disruptions in the ROCK/MLCK/myosin pathway. At the studied concentrations, cyclosporine A and chlorpromazine induced early ROCK activity, resulting in permanent MLC2 phosphorylation and BC constriction. However, fasudil reduced ROCK activity and caused rapid, substantial and permanent MLC2 dephosphorylation, leading to BC dilation. The remaining compounds (1-naphthyl isothiocyanate, deoxycholic acid and bosentan) caused BC dilation without modulating ROCK activity, although they were associated with a steady decrease in MLC2 phosphorylation via MLCK. These changes were associated with a common loss of BC contractions and failure of BA clearance. These results provide the first demonstration that cholestatic drugs alter BC dynamics by targeting the ROCK/MLCK pathway; in addition, they highlight new insights into the mechanisms underlying bile flow failure and can be used to identify new predictive biomarkers of drug-induced cholestasis.