Caffeine Suppresses the Activation of Hepatic Stellate Cells cAMP-Independently by Antagonizing Adenosine Receptors.

During liver injury, hepatic stellate cells (HSCs) are activated by various cytokines and transdifferentiated into myofibroblast-like activated HSCs, which produce collagen, a major source of liver fibrosis. Therefore, the suppression of HSC activation is regarded as a therapeutic target for liver fibrosis. Several epidemiological reports have revealed that caffeine intake decreases the risk of liver disease. In this study, therefore, we investigated the effect of caffeine on the activation of primary HSCs isolated from mice. Caffeine suppressed the activation of HSC in a concentration-dependent manner. BAPTA-AM, an intracellular Ca2+ chelator, had no effect on the caffeine-induced suppression of HSC activation. None of the isoform-selective inhibitors of phosphodiesterase1 to 5 affected changes in the morphology of HSC during activation, whereas CGS-15943, an adenosine receptor antagonist, inhibited them. Caffeine had no effect on intracellular cAMP level or on the phosphorylation of extracellular signal-regulated kinase (ERK)1/2. In contrast, caffeine significantly decreased the phosphorylation of Akt1. These results suggest that caffeine inhibits HSC activation by antagonizing adenosine receptors, leading to Akt1 signaling activation.

[Pathophysiology and mechanisms of postoperative cognitive dysfunction].

Postoperative cognitive impairment is a recognized clinical phenomenon. Previously, such clinical findings were called "adverse cerebral effects of anesthesia on old people". POCD is transient disturbance that can affect patients of any age but is more common in elderly people. Its relevance with the immediate post-operative phase was made clear. The aging of the population and new developments in medicine both lead to the increasing number of elderly patietnts undergoing extensive surgery. Mechanism of POCD is considered to be due to the inflammatory response and Ca2+ dysregulation of the brain. For the diagnosis of POCD, pscychometric tests are applied. Risk factors for POCD are aging, extensive invasive operations, intra and postoperative complications, and anesthetics. To reduce POCD, it is necessary to provide preoperative screening and cognitive training, minimally invasive surgery, the use of short-acting agents, meticulous anesthetic technique to prevent perioperative disturbances of homeostasis and organ ischemia, tight volume balance, and EEG monitoring.

Quantitative real-time measurement of endothelin-1-induced contraction in single non-activated hepatic stellate cells.

Although quiescent hepatic stellate cells (HSCs) have been suggested to regulate hepatic blood flow, there is no direct evidence that quiescent HSCs display contractile abilities. Here, we developed a new method to quantitatively measure the contraction of single isolated HSCs and evaluated whether endothelin-1 (ET-1) induced contraction of HSCs in a non-activated state. HSCs isolated from mice were seeded on collagen gel containing fluorescent beads. The beads around a single HSC were observed gravitating toward the cell upon contraction. By recording the movement of each bead by fluorescent microscopy, the real-time contraction of HSCs was quantitatively evaluated. ET-1 induced a slow contraction of non-activated HSCs, which was inhibited by the non-muscle myosin II inhibitor blebbistatin, the calmodulin inhibitor W-7, and the ETA receptor antagonist ambrisentan. ET-1-induced contraction was also largely reduced in Ca2+-free conditions, but sustained contraction still remained. The tonic contraction was further diminished by the Rho-kinase inhibitor H-1152. The mRNA expression of P/Q-type voltage-dependent Ca2+ channels (VDCC), as well as STIM and Orai, constituents of store-operated channels (SOCs), was observed in mouse non-activated HSCs. ET-1-induced contraction was not affected by amlodipine, a VDCC blocker, whereas it was partly reduced by Gd3+ and amiloride, non-selective cation channel blockers. However, neither YM-58483 nor SKF-96365, which inhibit SOCs, had any effects on the contraction. These results suggest that ET-1 leads to Ca2+-influx through cation channels other than SOCs and produces myosin II-mediated contraction of non-activated HSCs via ETA receptors, as well as via mechanisms involving Ca2+-calmodulin and Rho kinase.

Translational Studies on Anti-Atrial Fibrillatory Action of Oseltamivir by its in vivo and in vitro Electropharmacological Analyses.

Oseltamivir has been shown to prolong the atrial conduction time and effective refractory period, and to suppress the onset of burst pacing-induced atrial fibrillation in vitro. To better predict its potential clinical benefit as an anti-atrial fibrillatory drug, we performed translational studies by assessing in vivo anti-atrial fibrillatory effect along with in vivo and in vitro electropharmacological analyses. Oseltamivir in intravenous doses of 3 (n = 6) and 30 mg/kg (n = 7) was administered in conscious state to the persistent atrial fibrillation model dogs to confirm its anti-atrial fibrillatory action. The model was prepared by tachypacing to the atria of chronic atrioventricular block dogs for > 6 weeks. Next, oseltamivir in doses of 0.3, 3 and 30 mg/kg was intravenously administered to the halothane-anesthetized intact dogs to analyze its in vivo electrophysiological actions (n = 4). Finally, its in vitro effects of 10-1,000 µM on IK,ACh, IKur, IKr, INa and ICaL were analyzed by using cell lines stably expressing Kir3.1/3.4, KV1.5, hERG, NaV1.5 or CaV1.2, respectively (n = 3 for IK,ACh and IKr or n = 6 for IKr, INa and ICaL). Oseltamivir in doses of 3 and 30 mg/kg terminated the atrial fibrillation in 1 out of 6 and in 6 out of 7 atrial fibrillation model dogs, respectively without inducing any lethal ventricular arrhythmia. Its 3 and 30 mg/kg delayed inter-atrial conduction in a frequency-dependent manner, whereas they prolonged atrial effective refractory period in a reverse frequency-dependent manner in the intact dogs. The current assay indicated that IC50 values for IK,ACh and IKr were 160 and 231 µM, respectively, but 1,000 µM inhibited INa, ICaL and IKur by 22, 19 and 13%, respectively. The extent of INa blockade was enhanced at faster beating rate and more depolarized resting membrane potential. Oseltamivir effectively terminated the persistent atrial fibrillation, which may be largely due to the prolongation of the atrial effective refractory period and inter-atrial conduction time induced by IK,ACh and IKr inhibitions along with INa suppression. Thus, oseltamivir can exert a powerful anti-atrial fibrillatory action through its ideal multi-channel blocking property; and oseltamivir would become a promising seed compound for developing efficacious and safe anti-atrial fibrillatory drugs.