Statins, a group of drugs used for the treatment of hypercholesterolemia, have adverse effects on skeletal muscle. The symptoms of these effects range from slight myalgia to severe rhabdomyolysis. The number of patients currently taking statins is estimated to be several millions worldwide. However, the mechanism of statins’ myotoxic effects is unclear. Statins inhibit biosynthesis of mevalonate, a rate-limiting step of cholesterol synthesis, by inhibiting HMG-CoA reductase. Mevalonate is also an essential precursor for producing isoprenoids such as farnesylpyrophosphate and geranylgeranylpyrophosphate. These isoprenoids are especially important for anchoring small GTPases to the membrane before they function; e.g., Ras GTPases modulate proliferation and apoptosis, Rho GTPases control cytoskeleton formation, and Rab GTPases are essential for intracellular vesicle trafficking. Inactivation of these small GTPases alters cellular functions. Recently, we successfully reproduced statin-induced myotoxicity in culture dishes using in vitro skeletal muscle systems (e.g., skeletal myotubes and myofibers). This review summarizes our findings that statins induce depletion of isoprenoids and inactivation of small GTPases, especially Rab, which are critical for statin-induced myotoxicity. Although further study is required, our findings may contribute to the prevention and treatment of statins’ adverse effects on skeletal muscle and development of safer anti-hypercholesterolemia drugs.

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An involvement of inducible nitric oxide (NO) synthase (NOS) in pancreatic β-cell degeneration during the process of type 1 diabetes has been well discussed. Recently, there is growing evidence for pivotal roles of constitutive NOS (cNOS) in β-cells; the presence of NOS1 and NOS3 in pancreatic β-cells and the effects of low-concentration NO, which is assumed to be derived from cNOS, on β-cell functions have been reported. However, the roles of cNOS-derived NO in β-cells are still under debate. One of the reasons seems to be that NO has multiple biological activities, which are dependent on its concentration. In β-cells, NO has been shown to exert positive and negative regulation of insulin secretion and anti- and pro-apoptotic activities, which is likely to be dependent on concentrations. In this review article, we will describe the current understanding of the roles of NO in pancreatic β-cells, especially focusing on cNOS-derived NO and its differential roles depending on concentrations.

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Neuropathic pain, which is intolerable and persistent, arises as a direct consequence of a lesion or disease affecting the somatosensory system and can be debilitating for the affected patients. Accumulating evidence from animal studies has revealed the potential molecular basis for neuropathic pain, resulting in many promising therapeutic targets. While efforts at drug discovery have been made, conventional pharmacotherapy, including the use of opioid analgesics, is still insufficient for the relief of neuropathic pain. Therefore, novel target molecules that may lead to the development of promising analgesics are eagerly anticipated for improved treatment of neuropathic pain. In various insults such as sepsis and ischemia, high-mobility group box 1 (HMGB1) is released extracellularly to induce inflammation. HMGB1 was originally identified as a ubiquitous nuclear protein, but emerging evidence has suggested that HMGB1 also plays a role in neuroinflammation as a pro-inflammatory mediator. These findings suggest that HMGB1 may be involved in the pathology of neuropathic pain. In fact, some reports demonstrate an involvement of HMGB1 in the development and maintenance of neuropathic pain in experimental animals. Here, we overview the characteristics of HMGB1 as a pro-inflammatory mediator and show the promise of HMGB1 as a therapeutic target for neuropathic pain.

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Calcium is a ubiquitous intracellular signaling molecule required for initiating and regulating neuronal functions. Ca²⁺ release from intracellular stores in the endoplasmic reticulum into intracellular spaces via intracellular Ca²⁺–releasing channels, inositol 1,4,5-trisphosphate receptors (IP₃Rs) and ryanodine receptors (RyRs), is one mechanism altering the intracellular Ca²⁺ concentration. Functional abnormalities in endoplasmic calcium channels can disturb cellular calcium homeostasis and, in turn, produce pathological conditions. Indeed, our recent studies have indicated the involvement of these upregulated calcium channels in development of the rewarding effect of a drug of abuse and the suppression of its rewarding effect by calcium-channel inhibitors, which suggests a possible functional relationship between intracellular dynamics and the development of the rewarding effects induced by an abused drug. Although previous reports showed that the most important regulators of both RyR and IP₃R channel functions are changes in the intracellular Ca²⁺ concentration and in phosphorylation of these channels by numerous kinases and calcium modulators, little information is available to clarify how the expression of intracellular calcium channels is regulated. In this review, we therefore introduce the roles and regulatory mechanisms of intracellular calcium channels in drug dependence, especially in the rewarding effect induced by the abused drug.

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Recent studies have shown that lipid metabolism is regulated through the orchestration of multiple organs. Gut microbiota influences the metabolism of the liver through the production of fatty acids and phosphatidylcholine as well as the modulation of bile acid profile. Microbiota also affects the cardiovascular system through the production of metabolites from nutrients. MicroRNAs (miRNAs) are non-coding RNAs comprised of around 22 nucleotides in length. MiRNAs are released into blood flow from organs and interfere with the gene expression of target organs. MiRNAs are involved in the regulation of metabolic homeostasis including lipoprotein production and cardiovascular functions. Fatty acids are also circulating and distributed to each organ by fatty acid transporting proteins. Fatty acids can act as a ligand of G protein–coupled receptors, such as GPR41 and GPR43, and nuclear receptor PPARα, which bear crucial roles in the regulation of energy expenditure. Therefore the inter-organ communication plays important roles in the systematic regulation of lipid metabolism. Studies on the inter-organ network system will contribute to the development of diagnostic and therapeutic strategies for metabolic diseases. This review discusses how lipid metabolism is regulated by the inter-organ communication, focusing on the network axis between the liver, intestine, and heart.

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We investigated the effects of Ginkgo biloba extract (GBE) and ginkgolide (GLD) on human ether-a-go-go-related gene (hERG)-encoded K⁺ channels and its underlying mechanisms in the hERG-HEK293 cell line by determining GBE- and GLD-induced changes in action potential duration (APD), L-type calcium currents (I_Ca-L), and the intracellular calcium concentration ([Ca²⁺]_i) in guinea-pig ventricular myocytes. hERG currents, APD and I_Ca-L were recorded using the whole-cell patch clamp technique, the [Ca²⁺]_i was examined by an immunofluorescence experiment. In the present study, we found that a low concentration of GBE (0.005 mg/ml) increased hERG currents, but the high concentration of GBE (from 0.05 to 0.25 mg/ml) reduced hERG currents. GLD reduced hERG currents in a concentration-dependent manner (from 0.005 to 0.25 mg/ml). Both GBE and GLD altered kinetics of the hERG channel. GBE accelerated the activation of hERG channels without changing the inactivation curve, but reduced the time constant of inactivation; GLD did not shift the activation or the inactivation curve, but only reduced the time constant of inactivation. Both GBE and GLD shortened the APD, inhibited the I_Ca-L currents, and decreased the [Ca²⁺]_i in isolated guinea-pig ventricular myocytes. The results indicate that GBE and GLD can prevent ischemic arrhythmias and have an antiarrhythmic effect potential via inhibition of I_Kr and I_Ca-L currents.

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It is reported that liver hydrolysate (LH) enhances liver function. However, the effects of LH on physical fatigue are unknown. The aim of this study was to investigate the effect of LH on alterations in locomotor activity and energy metabolism such as 5′-AMP-activated protein kinase (AMPK), glycogen content, and blood lactic acid, after forced walking. Adult male ddY mice were used. Locomotor activity, AMPK phosphorylation, and glycogen content in the liver and soleus muscle, as well as blood lactic acid were determined following LH treatment before and/or after forced walking. The locomotor activity significantly decreased after forced walking for 3 h. Two administrations of LH (30 or 100 mg/kg) significantly increased the locomotor activity, while a single administration either before or after forced walking did not show any specific effect. Administering LH twice activated AMPK in the liver and soleus muscle. Glycogen levels significantly decreased in both the liver and soleus muscle after forced walking, whereas the blood lactate level significantly increased. In contrast, administering LH twice increased muscle glycogen and decreased blood lactic acid. These findings indicate that LH produced an anti-fatigue effect and that this effect appears to involve the efficient glycogen utilization through activation of AMPK.

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It is generally accepted that an increase in the myocardial level of heat-shock protein 72 (HSP72) protects viable cardiac tissue against myocardial infarction (MI)-induced stress. However, the induction of HSP72 after exposure to heat shock (HS) is blunted in the failing rat heart following MI. The mechanisms underlying this impairment in the HSP72 induction ability of the failing heart are not yet clearly defined. In the present study, we examined the involvement in heat-shock factor 1 (HSF1), a transcription factor of HSPs, in decreased ability for HSP72 induction in the failing rat heart following MI. In the failing heart, nuclear translocation of the HSF1 after exposure to hyperthermia was markedly reduced, whereas HSF1 in the cytosolic fraction and the HSP90 chaperone complex containing HSF1, a repressor of HSF1, were increased. Treatment with an HSP90 inhibitor, 17-allylamino-17-demethoxygel-danamycin, appeared to dissociate the interaction of HSF1 with HSP90, and then induced HSP72 in the failing heart after exposure to hyperthermia. These results suggest that an increase in the multichaperone complex, especially the HSF1-HSP90 interaction, associated with attenuation of HSF1 translocation into the nucleus, was involved in the impairment of HS-induced HSP72 induction in the failing heart following MI.

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In the novel object recognition task, ZSET1446 (also coded as ST101) enhanced object recognition memory in mice and ameliorated cognitive impairment caused by scopolamine in rats. The enhancement induced by ZSET1446 in mice was abolished by injection of mechamylamine, a nonselective antagonist of nicotinic acetylcholine (ACh) receptors, or dihydro-β-erythroidine, a selective antagonist against the α4 subunit of nicotinic ACh receptors. These results suggest that the procognitive effect of ZSET146 is probably mediated by stimulation of nicotinic receptors. Memantine was also effective in these tests and concomitant administration of subeffective doses of ZSET1446 and memantine significantly ameliorated the cognitive performance in the novel object recognition task in both mice and rats. Moreover, oral administration of ZSET1446 or memantine increased the extracellular level of ACh in the hippocampus as compared with the control. Further, concomitant administration of subeffective doses of ZSET1446 and memantine significantly increased the extracellular level of ACh as compared with the group of ZSET1446 or memantine alone. These results suggest that these two compounds have a synergistic effect on the cognitive function possibly by synergistic increase in the extracellular level of ACh in the hippocampus, and that the combination therapy of these compounds might be effective in clinical settings.

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Hepatic triacylglycerol (TAG) homeostasis is maintained by carefully regulated balance between its synthesis and disposal. Impairment in this balance causes steatosis. The aims of this study were i) to uncover whether fibrates control TAG concentration through the action of adipose triglyceride lipase (ATGL) and ii) to compare the potency of the effects on ATGL expression and TAG concentration among fenofibrate, bezafibrate, and clofibric acid in the liver of rats. Treatments of rats with the three fibrates induced ATGL and concomitantly decreased hepatic TAG concentration. The upregulation of ATGL was likely mediated through the activation of peroxisome proliferator-activated receptor α. Fibrates also expanded capacity of fatty acid β-oxidation. Importantly, three fibric acids (fenofibric, bezafibric, and clofibric acids) that are active metabolites formed in the liver exhibited almost the same potency to elevate ATGL expression in vivo, despite the fact that there were considerable differences in this regard among fenofibrate, bezafibrate, and clofibric acid when compared on the basis of their dosage. These results suggest that ATGL represents a potential therapeutic target for ameliorating hepatic steatosis and that fibric acids are promising agents to ameliorate and/or protect against hepatic steatosis.

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To clarify the hypotensive mechanism of angiotensin II receptor–blockers (ARBs), drug concentrations in plasma and vascular tissues were measured using matrix-assisted laser desorption ionization time-of-flight mass spectrometry and imaging mass spectrometry. In spontaneously hypertensive rats, systolic blood pressure (SBP) was measured 2 and 24 h after administration of candesartan cilexetil (0.3, 1, or 3 mg/kg) or azilsartan (0.3, 1, or 3 mg/kg). SBP was similarly lowered 2 h after administration of azilsartan or candesartan cilexetil, but it was significantly lower in the azilsartan-treated group than in the candesartan cilexetil-treated group at 24 h. Angiotensin II–induced vascular contractions were similarly attenuated 2 h after administration of these drugs, and the contractions were significantly lower in the azilsartan-treated group at 24 h. Although plasma concentration was significantly lower in the azilsartan-treated group at 24 h, vascular concentration of azilsartan was significantly greater than that of candesartan. Significant correlations between SBP and vascular concentrations were observed both at 2 and 24 h, while no significant correlation was observed between plasma and vascular concentrations. In conclusion, the mechanism of ARB-induced hypotension is likely to depend on vascular concentrations rather than plasma concentrations.

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It has been suggested that N,N-di-n-propyl-dopamine (dopamine analogue) decreased heart rate in rats through stimulation of dopamine receptors. Nevertheless, the role of prejunctional dopamine D_1/2-like receptors or even α₂-adrenoceptors to mediate cardiac sympatho-inhibition induced by dopamine remains unclear. Hence, this study identified the pharmacological profile of the cardiac sympatho-inhibition to dopamine in pithed rats. Male Wistar rats were pithed and prepared to stimulate the cardiac sympathetic outflow or to receive i.v. bolus of exogenous noradrenaline. I.v. continuous infusions of dopamine (endogenous ligand) or quinpirole (D₂-like agonist) dose-dependently inhibited the tachycardic responses to sympathetic stimulation, but not those to exogenous noradrenaline. In contrast, SKF-38393 (100 μg/kg∙min, D₁-like agonist) failed to modify both of these responses. The sympatho-inhibition to dopamine (1.8 μg/kg∙min) or quinpirole (100 μg/kg∙min): i) remained unaltered after saline or the antagonists SCH-23390 (D₁-like, 300 μg/kg) and rauwolscine (α₂-adrenoceptors, 300 μg/kg); and ii) was significantly antagonized by raclopride (D₂-like, 300 μg/kg). These antagonists, at the above doses, failed to modify the sympathetically-induced tachycardic responses. The above results suggest that the inhibition of the cardiac sympathetic outflow to dopamine and quinpirole is primarily mediated by prejunctional D₂-like receptors but not D₁-like receptors or α₂-adrenoceptors.

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The purpose of this study was to evaluate the angiogenic potency of ONO-1301, a novel prostacyclin agonist, using a murine sponge model. Solutions of ONO-1301 or hepatocyte growth factor (HGF), as a positive control, were injected into sponges in the backs of mice, daily for 14 days. Hemoglobin and HGF levels in the sponge were increased for up to 14 days on daily treatment with ONO-1301 while on HGF treatment, they peaked on day 7 and had decreased again by day 14. ONO-1301 also upregulated c-Met expression for 14 days in a dose-dependent manner. When the mice were pretreated with an antibody to HGF or the prostaglandin I (IP)-receptor antagonist CAY10441, the angiogenic effect of ONO-1301 was dramatically reduced. Plasma concentrations of cyclic adenosine monophosphate (cAMP) were increased in a dose-dependent manner by once daily treatment with ONO-1301 for 14 days. This effect was reduced by pretreatment with the IP-receptor antagonist. In conclusion, hemoglobin level was increased by repeated treatment with ONO-1301 for 14 days. It is suggested that ONO-1301 induced angiogenesis by promoting the synthesis of HGF and upregulated c-Met expression, followed by an increase in cAMP concentrations mediated by IP-receptor signaling.

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Several lines of evidence indicate that serotonin type 7 (5-HT₇) receptors play a critical role for non-photic resetting of the mammalian circadian clock; however, the contributions of other types of 5-HT receptors to non-photic entrainment are not yet clarified. The present study demonstrates that MKC-242, a selective 5-HT_1A receptor agonist, can evoke a non-photic-like phase-response in hamsters in vivo. This phase-shifting response to MKC-242 was antagonized not only by the selective 5-HT_1A receptor blocker WAY100635 but also by the selective 5-HT₇ receptor blocker DR4004. These suggest that synchronous activation of 5-HT_1A and 5-HT₇ receptors mediates non-photic signals to the hamster circadian clock.

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