Increased intracellular levels of Ca²⁺ are generally thought to negatively regulate lipolysis in mature adipocytes, whereas store-operated Ca²⁺ entry was recently reported to facilitate lipolysis and attenuate lipotoxicity by inducing lipophagy. Transient receptor potential mucolipin1 (TRPML1), a Ca²⁺-permeable non-selective cation channel, is mainly expressed on the lysosomal membrane and plays key roles in lysosomal homeostasis and membrane trafficking. However, the roles of TRPML1 in lipolysis remains unclear. In this study, we examined whether the channel function of TRPML1 induces lipolysis in mature adipocytes. We found that treatment of mature adipocytes with ML-SA1, a specific agonist of TRPML1, solely upregulated extracellular glycerol release, but not to the same extent as isoproterenol. In addition, knockdown of TRPML1 in mature adipocytes significantly reduced autophagic flux, regardless of ML-SA1 treatment. Our findings demonstrate that the channel function of TRPML1 partially contributes to lipid metabolism and autophagic membrane trafficking, suggesting that TRPML1, particularly the channel function of TRPML1, is as therapeutic target molecule for treating obesity.
Adipocytes ; Glycerol ; Homeostasis ; Isoproterenol ; Lipid Metabolism ; Lipolysis ; Membranes ; Obesity

Cardiac hypertrophy is a common pathological process of various cardiovascular diseases and eventually develops into heart failure. This paper was aimed to study the different pathological characteristics exhibited by different mouse strains after hypertrophy stimulation. Two mouse strains, A/J and FVB/nJ, were treated with isoproterenol (ISO) by osmotic pump to induce cardiac hypertrophy. Echocardiography was performed to monitor heart morphology and function. Mitochondria were isolated from hearts in each group, and oxidative phosphorylation function was assayed in vitro. The results showed that both strains showed a compensatory enhancement of heart contractile function after 1-week ISO treatment. The A/J mice, but not the FVB/nJ mice, developed significant cardiac hypertrophy after 3-week ISO treatment as evidenced by increases in left ventricular posterior wall thickness, heart weight/body weight ratio, cross sectional area of cardiomyocytes and cardiac hypertrophic markers. Interestingly, the heart from A/J mice contained higher mitochondrial DNA copy number compared with that from FVB/nJ mice. Functionally, the mitochondria from A/J mice displayed faster O
Animals ; Cardiomegaly/chemically induced* ; Heart Failure ; Isoproterenol/toxicity* ; Mice ; Mitochondria ; Myocytes, Cardiac/metabolism*

AIMTo observe the effect of LPC on the pacemaker current I(f) in ischemic myocardium and if the effect could be reversed by ISO.

METHODSBy using two microelectrode voltage clamp technique to measure and compare the amplitude of I(f) of ischemic myocardium in the presence of LPC and LPC add ISO.

RESULTSIschemia decreased the amplitude of I(f) at all membrane potential levels. Adding LPC 2 x 10(-5) mol/L to the ischemia-like solution, the amplitude of I(f) decreased further (n = 5, P < 0.05), it means that LPC aggravated the inhibitory effect of "ischemia" on the pacemaker activity. Adding LPC 2 x 10(-5) mol/L and ISO 1 x 10(-6) mol/L together to the ischemia-like solution, the amplitude of I(f) increased significantly at membrane potential -90 mV to - 120 mV (n = 8, P < 0.05) compared with ischemia condition, but still did not reach the levels before ischemia.

CONCLUSIONIn acute myocardial ischemia condition, toxic metabolite LPC accentuated its inhibitory effect on pacemaker current I(f), a local release and accumulation of catecholamine could not completely reverse their inhibitory effect.

Animals ; Isoproterenol ; metabolism ; Lysophosphatidylcholines ; pharmacology ; Membrane Potentials ; drug effects ; Microelectrodes ; Myocardial Ischemia ; metabolism ; physiopathology ; Myocardium ; Patch-Clamp Techniques ; Sheep

A large number of β-adrenergic receptor (β-AR) agonists and antagonists are widely used in the treatment of cardiovascular diseases and other diseases. Nonetheless, it remains unclear whether these commonly used β-AR drugs can activate downstream β- arrestin-biased signaling pathways. The objective of this study was to investigate β-arrestin2 recruitment effects of β-AR agonists and antagonists that were commonly used in clinical practice. We used TANGO (transcriptional activation following arrestin translocation) assay to detect the β-arrestin2 recruitment by β-AR ligands in HEK293 cell line (HTLA cells) stably transfected with tetracycline transactivator protein (tTA) dependent luciferase reporter and β-arrestin2-TEV fusion gene. Upon activation of β-AR by a β-AR ligand, β-arrestin2 was recruited to the C terminus of the receptor, followed by cleavage of the G protein-coupled receptors (GPCRs) fusion protein at the TEV protease-cleavage site. The cleavage resulted in the release of tTA, which, after being transported to the nucleus, activated transcription of the luciferase reporter gene. The results showed that β-AR non-selective agonists epinephrine, noradrenaline and isoprenaline all promoted β-arrestin2 recruitment at β1-AR and β2-AR. β1-AR selective agonists dobutamine and denopamine both promoted β-arrestin2 recruitment at β1-AR. β2-AR selective agonists procaterol and salbutamol promoted β-arrestin2 recruitment at β2-AR. β-AR non-selective antagonists alprenolol and pindolol promoted β-arrestin2 recruitment at β1-AR. β1-AR selective antagonists celiprolol and bevantolol showed β-arrestin2 recruitment at β1-AR. β2-AR selective antagonists butoxamine showed β-arrestin2 recruitment at β1-AR. These results provide some clues for the potential action of β-AR drugs, and lay a foundation for the screening of β-arrestin-biased β-AR ligands.
Humans ; beta-Arrestin 2/metabolism* ; HEK293 Cells ; Adrenergic beta-Agonists/pharmacology* ; Isoproterenol/pharmacology* ; Receptors, Adrenergic, beta-2/metabolism* ; Norepinephrine/pharmacology*

OBJECTIVETo explore the effects of Sini Decoction (SD) on the expressions of Samd2 and Smad7 isoproterenol (Iso) induced myocardial fibrosis rats.

METHODSTotally 19 Wistar rats were randomly divided into 3 groups, i.e., the control group, the model group, and the SD group. Iso was injected to rats in the model group and the SD group, while normal saline was injected to rats in the control group. SD was given to rats in the SD group by gastrogavage, while normal saline was administered to rats in the control group and the model group by gastrogavage. Four weeks later Masson staining and electron microscopic analysis were performed in each group. The protein and mRNA expressions of Smad2 and Smad7 were detected using immunohistochemical assay and RT-PCR.

RESULTSMasson staining showed the IOD value of the myocardial collagen fiber was 9 303 in the model group, 2 459 in the SD group, and 4 224 in the control group, indicating the myocardial fibrosis was more obvious in the model group than in the SD group and the control group. The IOD value of Smad2 protein was 20 275 and the mRNA IOD of Smad2 protein was 0. 919 in the model group, while they were respectively 9 949 and 0. 561 in the SD group, indicating the protein and mRNA expressions of Smad2 were obviously higher in the model group than in the SD group (P < 0.05). The IOD value of Smad7 protein was 25 667 and the mRNA IOD of Smad7 protein was 0.222 in the model group, while they were respectively 93 147 and 0. 412 in the SD group, indicating the protein and mRNA expressions of Smad7 was obviously lower in the model group than in the SD group (P < 0.05).

CONCLUSIONSD could effectively inhibit Iso induced myocardial fibrosis, and its mechanism may be associated with down-regulating the expression of Smad2 and up-regulating the expression of Smad7.

Animals ; Cardiomyopathies ; metabolism ; pathology ; Drugs, Chinese Herbal ; pharmacology ; Fibrosis ; Isoproterenol ; adverse effects ; Male ; Myocardium ; metabolism ; pathology ; Rats ; Rats, Wistar ; Smad2 Protein ; metabolism ; Smad7 Protein ; metabolism

Hyperphosphorylated microtubule-associated protein tau is the major protein component of neurofibrillary tangles in the brain of patients with Alzheimer's disease (AD). Until now, there is no effective cure to arrest this hyperphosphorylation. The present study was designed to explore the in vivo preventive effect of melatonin on Alzheimer-like tau hyperphosphorylation. Isoproterenol, a beta-receptor agonist, was used to induce tau hyperphosphorylation, and for preventive effect of melatonin, the rats were injected intraperitoneally with melatonin for 5 d before hippocampi infusion of isoproterenol. The level of tau phosphorylation was detected by Western blot and immunohistochemistry using sites specific antibodies (PHF-1 and Tau-1), and it was normalized by non-phosphorylation dependent total tau antibody (111e). The results by Western blot showed that the immunoreaction of tau at PHF-1 epitope was enhanced, and the reaction at Tau-1 epitope was weakened significantly at 48 h after injection of isoproterenol, suggesting hyperphosphorylation of tau at Ser 396/Ser 404 (PHF-1) and Ser199/Ser 202 (Tau-1) sites. Similar results were observed by immunohistochemistry staining, in which hyperphosphorylated tau was mainly detected in mossy fibers of hippocampal CA3 region. Pre-injection of rats with melatonin intraperitoneally arrested effectively the isoproterenol-induced tau hyperphosphorylation at both Tau-1 and PHF-1 sites, implying the preventive effect of melatonin in Alzheimer-like tau hyperphosphorylation.
Alzheimer Disease ; metabolism ; Animals ; Brain ; metabolism ; Isoproterenol ; administration & dosage ; antagonists & inhibitors ; Male ; Melatonin ; pharmacology ; Neurofibrillary Tangles ; drug effects ; metabolism ; Phosphorylation ; drug effects ; Rats ; Rats, Wistar ; tau Proteins ; metabolism

Animals ; Cell Survival ; Cells, Cultured ; GTP-Binding Proteins ; metabolism ; Isoproterenol ; adverse effects ; Myocytes, Cardiac ; cytology ; drug effects ; metabolism ; Rats ; Rats, Sprague-Dawley ; Receptors, Adrenergic, beta-2 ; metabolism

OBJECTIVETo explore the feasibility of intraperitoneal injection of isoproterenol (ISO) to induce cardiac remodeling in FVB/N mice.

METHODSForty-eight FVB/N mice were divided into back subcutaneous saline group (subcutaneous saline group), intraperitoneal saline group, back subcutaneous ISO group (subcutaneous ISO group), and intraperitoneal ISO group according to the route of administration of saline or ISO. ISO (30 μg/g body weight/day) was given to the subcutaneous ISO group and the intraperitoneal ISO group, twice daily with an interval of 12 hours, for 14 consecutive days. The subcutaneous saline group and the intraperitoneal saline group were injected with an equal volume of saline. The left ventricular end-diastolic posterior wall thickness was measured by echocardiography, and the ratio of heart weight to tibia length was determined. Hematoxylin-eosin staining was used to determine the myocardial fiber diameter. Picric-sirius red staining was used to determine the myocardial collagen deposition area. Quantitative real-time PCR was used to measure the mRNA expression of collagen I.

RESULTSCompared with the subcutaneous ISO, subcutaneous saline, and intraperitoneal saline groups, the intraperitoneal ISO group had increased sizes of the cardiac cavity and the heart. Compared with the subcutaneous saline and intraperitoneal saline groups, the subcutaneous ISO group showed no significant changes in the gross morphology of the cardiac cavity and the heart. The intraperitoneal ISO group showed significant increases in the ratio of heart weight to tibia length, myocardial fiber diameter, left ventricular end-diastolic posterior wall thickness, myocardial collagen area percentage, and the mRNA expression of collagen I compared with the subcutaneous ISO, subcutaneous saline, and intraperitoneal saline groups (P<0.01). There were no significant differences in the above five indices between the subcutaneous ISO group and the subcutaneous saline and intraperitoneal saline groups (P>0.05). No significant difference in the mortality rate was found between the subcutaneous ISO and intraperitoneal ISO groups (P>0.05).

CONCLUSIONSIntraperitoneal injection of ISO can induce cardiac hypertrophy and fibrosis in FVB/N mice.

Animals ; Atrial Remodeling ; drug effects ; Cardiovascular Diseases ; drug therapy ; metabolism ; pathology ; physiopathology ; Collagen ; metabolism ; Disease Models, Animal ; Humans ; Injections, Intraperitoneal ; Isoproterenol ; administration & dosage ; Male ; Mice ; Myocardium ; metabolism ; pathology

OBJECTIVETo explore the effect of extracellular signal regulated kinase 1/2 (ERK1/2) on edaravone (EDA)-triggered protection against myocardial toxicity induced by isoprenaline (ISO) in H9c2 myocardial cells (H9c2 cells).

METHODSH9c2 cells were exposed to ISO at different concentrations to establish a cardiac toxicity model induced by persistent excitation of β1 receptor. EDA was added before ISO as a pretreatment. PD-98059, an ERK1/2 inhibitor, was administered 1 h prior to EDA to inhibit the phosphorylation of ERK1/2. Cell viability was measured using cell counter kit (CCK-8). The expressions of p-ERK1/2 and t-ERK1/2 were tested by Western blotting. Mitochondrial membrane potential (MMP) was detected by Rhodamine123 (Rh123) staining and photofluorography.

RESULTSExposure of H9c2 cells to 80 µmol/L ISO for 24 h down-regulated ERK1/2 phosphorylation and repressed MMP. Pretreatment with 10-40 µmol/L EDA for 1 h inhibited ISO-induced myocardial toxicity and pretreatment of 40 µmol/L EDA partially rescued ERK1/2 phosphorylation and MMP level. PD-98059 abolished cardiac protection of EDA, leading to myocardial toxicity and MMP loss.

CONCLUSIONEDA can protect H9c2 cells against myocardial injury induced by ISO by suppressing ISO-triggered inhibition of ERK1/2 activation.

Animals ; Antipyrine ; analogs & derivatives ; pharmacology ; Cell Line ; Flavonoids ; pharmacology ; Isoproterenol ; toxicity ; MAP Kinase Signaling System ; Mitogen-Activated Protein Kinase 3 ; metabolism ; Myocytes, Cardiac ; drug effects ; metabolism ; Phosphorylation ; Rats

OBJECTIVETo investigate the effects of microRNA-133a on isoproterenol (ISO)-induced neonatal rat cardiomyocyte hypertrophy and related molecular mechanism focusing on the changes of L-type calcium channel α1C subunit.

METHODSNeonatal rat cardiomyocytes were cultured, cardiomyocyte hypertrophy was induced by isoproterenol (ISO, 10 µmol/L). The cell surface area was measured by phase contrast microscope and Leica image analysis system. The mRNA expressions of atrial natriuretic peptide (ANP), β-myosin heavy chain (β-MHC), miR-133a and the α1C were detected by qRT-PCR. The protein expression of α1C was evaluated by Western blot. MiR-133a mimic was transfected into cardiomyocytes to investigate the effects of miR-133a on ISO-induced cardiomyocyte hypertrophy. The targets of miR-133a were predicted by online database Targetscan. The 3' untranslated region sequence of α1C was cloned into luciferase reporter vector and then transiently transfected into HEK293 cells. The luciferase activities of samples were measured to verify the expression of luciferase reporter vector. The expression level of α1C was inhibited by RNAi to determine the effects of α1C on cardiomyocyte hypertrophy. Intracellular Ca(2+) content was measured by confocal laser microscope.

RESULTS(1) The expression of miR-133a was significantly reduced in ISO-induced cardiomyocyte hypertrophy (P < 0.01) . Upregulating miR-133a level could suppress the increase of cell surface area, the mRNA expression of ANP and β-MHC (P < 0.01) . (2) α1C was the one of potential target of miR-133a by prediction using online database Targetscan. The luciferase activities of HEK293 cells with the plasmid containing wide type α1C 3'UTR sequence were significantly decreased compared with control group (P < 0.01) . Upregulation of the miR-133a level by miR-133a mimic transfection could suppress the protein expression of α1C (P < 0.05) . (3) The expression of α1C was significantly increased in ISO treated cardiomyocytes (P < 0.05) . Downregulation of α1C by RNAi could markedly inhibit the increase of cell surface area, the mRNA expression of ANP and β-MHC (P < 0.01, P < 0.05, P < 0.05). (4) Downregulation of α1C expression by RNAi or upregulation of miR-133a level by miR-133a mimic transfection significantly inhibited intracellular Ca(2+) content (P < 0.01) .

CONCLUSIONSOur data confirms that α1C is the target of miR-133a. MiR-133a can negatively regulate the expression of L-type calcium α1C subunit, resulting in the decrease of intracellular Ca(2+) content and the attenuation of ISO-induced cardiomyocyte hypertrophy.

Animals ; Calcium Channels, L-Type ; metabolism ; Cell Enlargement ; drug effects ; Cells, Cultured ; Isoproterenol ; pharmacology ; MicroRNAs ; genetics ; Myocytes, Cardiac ; drug effects ; metabolism ; pathology ; Rats ; Rats, Sprague-Dawley ; Transfection