Ardipusilloside-I stimulates gastrointestinal motility and phosphorylation of smooth muscle myosin by myosin light chain kinase

Ardipusilloside-I is a natural triterpenoid saponin, which was isolated from Ardisia pusilla A. DC. The aim of the study was to evaluate the stimulation of ardipusilloside-I on gastrointestinal motility in vitro and in vivo. The experiment of smooth muscle contraction directly monitored the contractions of the isolated jejunal segment (IJS) in different contractile states, and the effects of ardipusilloside-I on myosin were measured in the presence of Ca²⁺-calmodulin using the activities of 20 kDa myosin light chain (MLC₂₀) phosphorylation and myosin Mg²⁺-ATPase. The effects of ardipusilloside-I on gastro emptying and intestinal transit in constipation-predominant rats were observed, and the MLCK expression in jejuna of constipated rats was determined by western blot. The results showed that, ardipusilloside-I increased the contractility of IJS in a dose-dependent manner and reversed the low contractile state (LCS) of IJS induced by low Ca²⁺, adrenaline, and atropine respectively. There were synergistic effects on contractivity of IJS between ardipusilloside-I and ACh, high Ca²⁺, and histamine, respectively. Ardipusilloside-I could stimulate the phosphorylation of MLC₂₀ and Mg²⁺-ATPase activities of Ca²⁺- dependent phosphorylated myosin. Ardipusilloside-I also stimulated the gastric emptying and intestinal transit in normal and constipated rats in vivo, respectively, and increased the MLCK expression in the jejuna of constipation-predominant rats. Briefly, the findings demonstrated that ardipusilloside-I could effectively excite gastrointestinal motility in vitro and in vivo.

Ameliorative effects of atractylodin on intestinal inflammation and co-occurring dysmotility in both constipation and diarrhea prominent rats

Intestinal disorders often co-occur with inflammation and dysmotility. However, drugs which simultaneously improve intestinal inflammation and co-occurring dysmotility are rarely reported. Atractylodin, a widely used herbal medicine, is used to treat digestive disorders. The present study was designed to characterize the effects of atractylodin on amelioration of both jejunal inflammation and the co-occurring dysmotility in both constipation-prominent (CP) and diarrhea-prominent (DP) rats. The results indicated that atractylodin reduced proinflammatory cytokines TNF-α, IL-1β, and IL-6 in the plasma and inhibited the expression of inflammatory mediators iNOS and NF-kappa B in jejunal segments in both CP and DP rats. The results indicated that atractylodin exerted stimulatory effects and inhibitory effects on the contractility of jejunal segments isolated from CP and DP rats respectively, showing a contractile-state-dependent regulation. Atractylodin-induced contractile-state-dependent regulation was also observed by using rat jejunal segments in low and high contractile states respectively (5 pairs of low/high contractile states). Atractylodin up-regulated the decreased phosphorylation of 20 kDa myosin light chain, protein contents of myosin light chain kinase (MLCK), and MLCK mRNA expression in jejunal segments of CP rats and down-regulated those increased parameters in DP rats. Taken together, atractylodin alleviated rat jejunal inflammation and exerted contractile-state-dependent regulation on the contractility of jejunal segments isolated from CP and DP rats respectively, suggesting the potential clinical implication for ameliorating intestinal inflammation and co-occurring dysmotility.

Effect of hydrogen sulfide on cardiac myosin light chain kinase expression in diabetic rats / 中南大学学报(医学版)

OBJECTIVE@#To investigate the effect of hydrogen sulfide (H2S) on cardiac myosin light chain kinase (MLCK) expression in diabetic rats.
@*METHODS@#A total of 32 male SD rats were randomly divided into a normal control group (NC group), a diabetic control group (DM), a NaHS treatment group (DM+NaHS) and a NaHS group (NaHS) (n=8 in each group). Intraperitoneal injection of streptozotocin was utilized to establish Type 1 diabetic rat model. The diabetic rats in the DM+NaHS and NaHS groups were intraperitoneally injected with 28 μmol/kg NaHS solution. Eight weeks later, the ventricular hemodynamic parameters, the ratio of heart weight/body weight (HW/BW ratio), the levels of lactate dehydrogenase (LDH) and creatine kinase MB isozyme (CK-MB) in serum were determined. The ultrastructures of myocardium were observed under electron microscopy. The expressions of MLCK mRNA and protein level in myocardium were detected by RT-PCR and Western blot, respectively.
@*RESULTS@#Compared with the NC group, there was no significant difference in the various indexes in the NaHS group (all P>0.05). The function of left ventricular contract and relaxation were decreased obviously in diabetic rats, while the HW/BW ratio was increased (all P<0.01). The levels of LDH and CK-MB were increased (both P<0.01) in serum, while the levels of MLCK mRNA and protein were decreased significantly (both P<0.01) in myocardial tissues. Compared with the DM group, the left ventricular hemodynamic parameters and myocardial ultrastructure damage were improved in the DM+NaHS group, while the HW/BW ratio was decreased (all P<0.05). The levels of LDH and CK-MB were decreased (both P<0.01), while the levels of MLCK mRNA and protein were increased significantly (both P<0.01).
@*CONCLUSION@#H2S can protect myocardium in diabetic rats, which may be associated with upregulation of cardiac MLCK.

Olanzapine May Inhibit Colonic Motility Associated with the 5-HT Receptor and Myosin Light Chain Kinase

OBJECTIVE: To study whether the effects of olanzapine on gastrointestinal motility is related to the serotonin antagonism and myosin light chain kinase. METHODS: Male Sprague-Dawley rats were randomly divided into four groups. Olanzapine gavage was performed for each treatment group during the course of 30 continuous days, while the same volume of saline was given to the rats in the control group. Defecation of the rats was observed on days 7 and 30 after olanzapine gavage. The effects of olanzapine on contraction of colonic smooth muscles were observed in ex vivo experiments. A Western blot was used to evaluate expression levels of the serotonin transporter (SERT) and MLCK in colon segments of the rats. RESULTS: ResultsaaCompared to the control group, 5-160 µM of olanzapine could inhibit dose-dependently the contraction of colonic smooth muscle ex vivo experiments. The maximum smooth muscle contraction effects of 5-HT and acetylcholine significantly decreased after treatment with 40-160 µM of olanzapine. Constipation was found in the olanzapine-treated rats on day 7 and have sustained day 30 after gavage. Expression of MLCK in olanzapine-treated rats was significantly decreased, whereas the expression of SERT significantly increased on the day 7, then significantly decreased on the day 30 after olanzapine gavage. CONCLUSION: SERT and MLCK may involve in the inhibition of colonic contraction induced by olanzapine.

Relationship between electrocardiographic and genetic mutation (MYH7-H1717Q, MYLK2-K324E and KCNQ1-R190W) phenotype in patients with hypertrophic cardiomyopathy / 中华心血管病杂志

<p><b>OBJECTIVE</b>To explore the relationship between electrocardiographic (ECG) and genetic mutations of patients with hypertrophic cardiomyopathy (HCM), and early ECG changes in HCM patients.</p><p><b>METHODS</b>Clinical, 12-lead ECG and echocardiographic examination as well as genetic examinations were made in a three-generation Chinses HCM pedigree with 8 family members (4 males). The clinical characterization and ECG parameters were analyzed and their relationship with genotypes in the family was explored.</p><p><b>RESULTS</b>Four missense mutations (MYH7-H1717Q, MYLK2-K324E, KCNQ1-R190W, TMEM70-I147T) were detected in this pedigree. The proband carried all 4 mutations and 5 members carried 2 mutations. Corrected QTc interval of KCNQ1-H1717Q carriers was significantly prolonged and was consistent with the ECG characterization of long QT syndrome. MYLK2-K324E and KCNQ1-R190W carriers presented with Q wave and(or) depressed ST segment, as well as flatted or reversed T waves in leads from anterolateral and inferior ventricular walls. ECG results showed ST segment depression, flat and inverted T wave in the gene mutation carriers with normal echocardiographic examination results. ECG and echocardiographic results were normal in TMEM70-I147T mutation carrier.</p><p><b>CONCLUSIONS</b>The combined mutations of the genes associated with cardiac ion channels and HCM are linked with the ECG phenotype changes in this HCM pedigree. The variations in ECG parameters due to the genetic mutation appear earlier than the echocardiography and clinical manifestations. Variation in ECG may become one of the indexes for early diagnostic screening and disease progression of the HCM gene mutation carriers.</p>

Modulatory effects of taurine on jejunal contractility

Taurine (2-aminoethanesulfonic acid) is widely distributed in animal tissues and has diverse pharmacological effects. However, the role of taurine in modulating smooth muscle contractility is still controversial. We propose that taurine (5-80 mM) can exert bidirectional modulation on the contractility of isolated rat jejunal segments. Different low and high contractile states were induced in isolated jejunal segments of rats to observe the effects of taurine and the associated mechanisms. Taurine induced stimulatory effects on the contractility of isolated rat jejunal segments at 3 different low contractile states, and inhibitory effects at 3 different high contractile states. Bidirectional modulation was not observed in the presence of verapamil or tetrodotoxin, suggesting that taurine-induced bidirectional modulation is Ca2+ dependent and requires the presence of the enteric nervous system. The stimulatory effects of taurine on the contractility of isolated jejunal segments was blocked by atropine but not by diphenhydramine or by cimetidine, suggesting that muscarinic-linked activation was involved in the stimulatory effects when isolated jejunal segments were in a low contractile state. The inhibitory effects of taurine on the contractility of isolated jejunal segments were blocked by propranolol and L-NG-nitroarginine but not by phentolamine, suggesting that adrenergic β receptors and a nitric oxide relaxing mechanism were involved when isolated jejunal segments were in high contractile states. No bidirectional effects of taurine on myosin phosphorylation were observed. The contractile states of jejunal segments determine taurine-induced stimulatory or inhibitory effects, which are associated with muscarinic receptors and adrenergic β receptors, and a nitric oxide associated relaxing mechanism.

Vascular O-GlcNAcylation augments reactivity to constrictor stimuli by prolonging phosphorylated levels of the myosin light chain

O-GlcNAcylation is a modification that alters the function of numerous proteins. We hypothesized that augmented O-GlcNAcylation levels enhance myosin light chain kinase (MLCK) and reduce myosin light chain phosphatase (MLCP) activity, leading to increased vascular contractile responsiveness. The vascular responses were measured by isometric force displacement. Thoracic aorta and vascular smooth muscle cells (VSMCs) from rats were incubated with vehicle or with PugNAc, which increases O-GlcNAcylation. In addition, we determined whether proteins that play an important role in the regulation of MLCK and MLCP activity are directly affected by O-GlcNAcylation. PugNAc enhanced phenylephrine (PE) responses in rat aortas (maximal effect, 14.2±2 vs 7.9±1 mN for vehicle, n=7). Treatment with an MLCP inhibitor (calyculin A) augmented vascular responses to PE (13.4±2 mN) and abolished the differences in PE-response between the groups. The effect of PugNAc was not observed when vessels were preincubated with ML-9, an MLCK inhibitor (7.3±2 vs 7.5±2 mN for vehicle, n=5). Furthermore, our data showed that differences in the PE-induced contractile response between the groups were abolished by the activator of AMP-activated protein kinase (AICAR; 6.1±2 vs 7.4±2 mN for vehicle, n=5). PugNAc increased phosphorylation of myosin phosphatase target subunit 1 (MYPT-1) and protein kinase C-potentiated inhibitor protein of 17 kDa (CPI-17), which are involved in RhoA/Rho-kinase-mediated inhibition of myosin phosphatase activity. PugNAc incubation produced a time-dependent increase in vascular phosphorylation of myosin light chain and decreased phosphorylation levels of AMP-activated protein kinase, which decreased the affinity of MLCK for Ca2+/calmodulin. Our data suggest that proteins that play an important role in the regulation of MLCK and MLCP activity are directly affected by O-GlcNAcylation, favoring vascular contraction.

Myosin light chain kinase is necessary for post-shock mesenteric lymph drainage enhancement of vascular reactivity and calcium sensitivity in hemorrhagic-shocked rats

Vascular hyporeactivity is an important factor in irreversible shock, and post-shock mesenteric lymph (PSML) blockade improves vascular reactivity after hemorrhagic shock. This study explored the possible involvement of myosin light chain kinase (MLCK) in PSML-mediated vascular hyporeactivity and calcium desensitization. Rats were divided into sham (n=12), shock (n=18), and shock+drainage (n=18) groups. A hemorrhagic shock model (40±2 mmHg, 3 h) was established in the shock and shock+drainage groups. PSML drainage was performed from 1 to 3 h from start of hypotension in shock+drainage rats. Levels of phospho-MLCK (p-MLCK) were determined in superior mesenteric artery (SMA) tissue, and the vascular reactivity to norepinephrine (NE) and sensitivity to Ca2+ were observed in SMA rings in an isolated organ perfusion system. p-MLCK was significantly decreased in the shock group compared with the sham group, but increased in the shock+drainage group compared with the shock group. Substance P (1 nM), an agonist of MLCK, significantly elevated the decreased contractile response of SMA rings to both NE and Ca2+ at various concentrations. Maximum contractility (Emax) in the shock group increased with NE (from 0.179±0.038 to 0.440±0.177 g/mg, P<0.05) and Ca2+ (from 0.515±0.043 to 0.646±0.096 g/mg, P<0.05). ML-7 (0.1 nM), an inhibitor of MLCK, reduced the increased vascular response to NE and Ca2+ at various concentrations in the shock+drainage group (from 0.744±0.187 to 0.570±0.143 g/mg in Emax for NE and from 0.729±0.037 to 0.645±0.056 g/mg in Emax for Ca2+, P<0.05). We conclude that MLCK is an important contributor to PSML drainage, enhancing vascular reactivity and calcium sensitivity in rats with hemorrhagic shock.

Structural insight into enhanced calcium indicator GCaMP3 and GCaMPJ to promote further improvement

Genetically encoded Ca(2+) indicators (GECI) are important for the measurement of Ca(2+) in vivo. GCaMP2, a widely-used GECI, has recently been iteratively improved. Among the improved variants, GCaMP3 exhibits significantly better fluorescent intensity. In this study, we developed a new GECI called GCaMPJ and determined the crystal structures of GCaMP3 and GCaMPJ. GCaMPJ has a 1.5-fold increase in fluorescence and 1.3-fold increase in calcium affinity over GCaMP3. Upon Ca(2+) binding, GCaMP3 exhibits both monomeric and dimeric forms. The structural superposition of these two forms reveals the role of Arg-376 in improving monomer performance. However, GCaMPJ seldom forms dimers under conditions similar to GCaMP3. St ructural and mutagenesis studies on Tyr-380 confirmed its importance in blocking the cpEGFP β-barrel holes. Our study proposes an efficient tool for mapping Ca(2+) signals in intact organs to facilitate the further improvement of GCaMP sensors.

Study on conditional myosin light chain kinase gene knockout mice resulting in hearing loss / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To investigate the function of myosin light chain kinase (MLCK) in hearing in mouse by generating inner hair cell-specific Mlck knockout mice and analyze the effect on their hearing.</p><p><b>METHODS</b>Cross Mlck floxed mice with IHC-Cre mice, the genotype and knockout efficiency were confirmed by PCR. We used auditory brain stem response (ABR) to evaluate mice hearing function at different frequencies.</p><p><b>RESULTS</b>Mlck knockout mice were selected by mice tail DNA genotyping and confirmed the deletion of the target gene by isolated inner hair cell DNA genotyping. Mlck-deficient mice showed impaired hearing with a rise in ABR threshold response to click and three different pure tones (8 kHz, 16 kHz, 32 kHz), and the rise was over 20 dB at high-frequency(32 kHz). Further analyses of waveforms showed that wave-I amplitudes on 60 dB SPL, 50 dB SPL and 40 dBSPL in response to tone (16 kHz) were less than control group(P < 0.05) on average, but the ratio of wave I/II and I/III were not difference (P > 0.05).</p><p><b>CONCLUSIONS</b>Mlck is successfully deleted in inner hair cell-specific Mlck knockout mice. Mlck knockout mice display a significantly higher threshold in response to click and tones, especially in high-frequencies.</p>

An experimental study on intestinal epithelial barrier dysfunction induced by interferon-gamma and tumor necrosis factor-alpha / 中华烧伤杂志

<p><b>OBJECTIVE</b>To investigate the effect of combination of interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α) on intestinal epithelial barrier function.</p><p><b>METHODS</b>The Caco-2 monolayers were cultured in DMEM nutrient solution, and then they were inoculated in 24-well or 6-well plate with Transwell inserts.They were divided into control group (ordinary treatment), IFN-γ group (with addition of 10 ng/mL IFN-γ), TNF-α group (with addition of 10 ng/mL TNF-α), and IFN-γ plus TNF-α group (with addition of 10 ng/mL TNF-α and 10 ng/mL IFN-γ). Monolayers inoculated in 24-well plate were collected for determination of transepithelial electrical resistance (TER) with an ohmmeter at post treatment hour (PTH) 0, 6, 12, 24, 36, and 48, the permeability of monolayers with fluorescein isothiocyanate-labeled dextran (FITC-dextran) tracer method at PTH 48, the distribution and morphological change of tight junction occludin with immunofluorescence assay at PTH 48. Monolayers inoculated in 6-well plate were collected for determination of protein expression of occludin, myosin light chain kinase (MLCK), and phosphorylated MLC (pMLC) with Western blot at PTH 24. Data were processed with one-way analysis of variance and t test.</p><p><b>RESULTS</b>(1) There was no obvious difference in TER in control group at each time point (F = 0.86, P > 0.05). TER in IFN-γ group and TNF-α group were gradually decreased during PTH 6-48, but showed no statistical difference as compared with that at PTH 0 (with F value respectively 1.69, 2.47, P values all above 0.05). TER in IFN-γ plus TNF-α group was significantly decreased from PTH 24 as compared with that at PTH 0 (t = 4.97, P < 0.05) and that in each of the other three groups (F = 11.54, P < 0.05). (2) The permeability of monolayers in IFN-γ plus TNF-α group [(1197 ± 215)pmol] was significantly higher than that in control group, IFN-γ group, and TNF-α group [(303 ± 93), (328 ± 76), (797 ± 177) pmol, with t value respectively 4.8, 5.0, 6.9, P values all below 0.01]. (3) There was no statistical difference in occludin expression at PTH 24 among four groups (F = 0.26, P > 0.05). The occludin in control group at PTH 48 was regular in arrangement, while that in IFN-γ and TNF-α groups was irregular in arrangement. The arrangement of occludin in IFN-γ plus TNF-α group at PTH 48 was interrupted, with obvious redistribution in cytoplasm. (4) The protein expression of pMLC in IFN-γ plus TNF-α group (0.95 ± 0.05) was significantly higher than that in control group, IFN-γ group, or TNF-α group (0.57 ± 0.12, 0.56 ± 0.07, 0.59 ± 0.10, respectively, F = 17.97, P < 0.01). The protein expression of MLCK in IFN-γ plus TNF-α group (1.57 ± 0.36) was also significantly higher than that in control, IFN-γ, TNF-α groups (0.85 ± 0.18, 1.04 ± 0.23, 1.00 ± 0.07, respectively, F = 9.05, P < 0.05).</p><p><b>CONCLUSIONS</b>Combination of IFN-γ and TNF-α can induce intestinal epithelial barrier dysfunction by up-regulating MLCK protein expression and promoting MLC phosphorylation.</p>

Role of asymmetric dimethylarginine in acute lung injury induced by cerebral ischemia/reperfusion injury in rats / 南方医科大学学报

<p><b>OBJECTIVE</b>To determine the role of asymmetric dimethylarginine (ADMA) in acute lung injury induced by cerebral ischemia/reperfusion (I/R) injury in rats.</p><p><b>METHODS</b>Adult male SD rats were randomly divided into 4 groups, namely the sham-operated group (S), cerebral I/R model group, ADMA+I/R group, and dimethylarginine dimethylaminohydrolase (DDAH)+I/R group. In the latter 3 groups, acute lung injury was induced by left middle cerebral artery occlusion for 120 min. After a 24-h reperfusion, the rats were sacrificed and the activities of nitric oxide synthase (NOS) and contents of nitric oxide (NO) were measured using reductase and colorimetric assay. The mRNA and protein expressions of protein kinase C (PKC) and myosin light chain kinase (MLCK) in the lung tissues were detected with RT-PCR and Western blotting, respectively. The contents of ADMA in the bronchoalveolar lavage fluid (BALF) and blood flowing into and out of the lungs were measured by ELISA.</p><p><b>RESULTS</b>Cerebral I/R injury caused significantly elevated ADMA levels in the BALF and blood flowing into the lungs, and obviously lowered the NO concentration and NOS activity in the lung tissues (P<0.05). Following cerebral I/R injury, MLCK and PKC mRNA and protein expressions were significantly upregualted in the lung tissues (P<0.05). Exogenous DDAH obviously decreased the levels of ADMA in the BALF and blood flowing into the lungs, increased NO concentration and NOS activity, and down-regulated MLCK and PKC mRNA and protein expressions in lung tissues of rats with cerebral I/R injury (P<0.05).</p><p><b>CONCLUSION</b>ADMA contributes to the development of acute lung injury following cerebral I/R injury in rats by upregulating MLCK and PKC expression. ADMA may serve as a novel therapeutic biomarker and a potential therapeutic target for acute lung injury induced by cerebral I/R injury.</p>

MLCK and PKC Involvements via Gi and Rho A Protein in Contraction by the Electrical Field Stimulation in Feline Esophageal Smooth Muscle

We have shown that myosin light chain kinase (MLCK) was required for the off-contraction in response to the electrical field stimulation (EFS) of feline esophageal smooth muscle. In this study, we investigated whether protein kinase C (PKC) may require the on-contraction in response to EFS using feline esophageal smooth muscle. The contractions were recorded using an isometric force transducer. On-contraction occurred in the presence of NG-nitro-L-arginine methyl ester (L-NAME), suggesting that nitric oxide acts as an inhibitory mediator in smooth muscle. The excitatory composition of both contractions was cholinergic dependent which was blocked by tetrodotoxin or atropine. The on-contraction was abolished in Ca2+-free buffer but reappeared in normal Ca2+-containing buffer indicating that the contraction was Ca2+ dependent. 4-aminopyridine (4-AP), voltage-dependent K+ channel blocker, significantly enhanced on-contraction. Aluminum fluoride (a G-protein activator) increased on-contraction. Pertussis toxin (a Gi inactivator) and C3 exoenzyme (a rhoA inactivator) significantly decreased on-contraction suggesting that Gi or rhoA protein may be related with Ca2+ and K+ channel. ML-9, a MLCK inhibitor, significantly inhibited on-contraction, and chelerythrine (PKC inhibitor) affected on the contraction. These results suggest that endogenous cholinergic contractions activated directly by low-frequency EFS may be mediated by Ca2+, and G proteins, such as Gi and rhoA, which resulted in the activation of MLCK, and PKC to produce the contraction in feline distal esophageal smooth muscle.

Comparing the effect of high frequency oscillatory ventilation and conventional mandatory ventilation on the myocardial function of rabbit with inhalation injury / 中华烧伤杂志

<p><b>OBJECTIVE</b>To compare the effect of high frequency oscillatory ventilation (HFOV) and conventional mandatory ventilation (CMV) on the myocardial function of rabbits with inhalation injury.</p><p><b>METHODS</b>Steam inhalation injury model was reproduced in 16 New Zealand albino rabbits. They were randomly divided into CMV group (n = 8) and HFOV group (n = 8) by drawing lots, and they received ventilation in metered volume and HFOV treatment respectively. Heart blood was drawn from rabbits before they were sacrificed 4 hours after treatment to determine the plasma activity of lactate dehydrogenase 1 (LDH1) and creatine phosphorylated kinase (CPK-MB). Myocardial tissue from left ventricle was harvested and homogenized to determine the concentration of TNF-α and IL-8, the activity of caspase-1, and the activity of myosin-light-chain kinase (MLCK) and the ATPase of myosin light chain (MLC-ATPase) by enzyme-linked immunosorbent assay, spectrophotometry, and the nuclide liquid scintillation technique respectively. Part of the myocardial tissue sample was examined pathologically. Data were processed with analysis of variance.</p><p><b>RESULTS</b>(1) The activities of LDH1 and CPK-MB in plasma were obviously higher in CMV group than in HFOV group [(643 ± 108), (342 ± 48) U vs. (233 ± 92), (186 ± 36) U, with F value respectively 10.326 and 9.846, P values all below 0.01]. (2) The contents of TNF-α, IL-8 and the activity of caspase-1 in myocardial tissue homogenate were obviously higher in CMV group than in HFOV group [(181 ± 35), (89 ± 19) pg/g, and (0.56 ± 0.27) g/g protein vs. (94 ± 21), (43 ± 11) pg/g, and (0.24 ± 0.12) g/g protein, with F value respectively 8.239, 7.826, 5.716, P values all below 0.01]. (3) The activities of MLC-ATPase and MLCK were lower in CMV group than in HFOV group [(0.24 ± 0.12) µmol×mg(-1)×min(-1), (3.3 ± 1.1) mmol×mg(-1)×min(-1) vs. (0.48 ± 0.16) µmol×mg(-1)×min(-1), (7.7 ± 1.7) mmol×mg(-1)×min(-1), with F value respectively 4.125, 4.766, P values all below 0.01]. (4) No obvious necrosis, degeneration or inflammatory cell infiltration was observed in myocardial tissue of rabbits in 2 groups under light microscope; but the myocardial fiber was slightly swollen, and it was less marked in the HFOV group.</p><p><b>CONCLUSIONS</b>The influence of HFOV on myocardial myosin phosphorylation system of rabbits with inhalation injury is less than that of CMV.</p>

Research on intestinal tight junction barrier dysfunction should be emphasized in burn injury / 中华烧伤杂志

Severe burn injury is often accompanied by intestinal epithelial tight junction barrier dysfunction, which is believed to be closely associated with postburn shock, inflammation, hypermetabolism, infection, organ dysfunction etc. Recent studies have documented the critical role of tight junction-associated protein regulation in intestinal epithelial barrier dysfunction induced by severe burn injury. Myosin light chain (MLC) phosphorylation regulated by both myosin light chain kinase, which can phosphorylate MLC directly, and Rho-associated kinase, which can inhibit MLC phosphatase and then induce MLC phosphorylation indirectly, play a critical role in intestinal epithelial tight junction barrier dysfunction which occurs in severe burn injury. Recent advances have provided new insights into the mechanisms and the therapeutic strategies of intestinal epithelial tight junction barrier dysfunction following severe burn injury.

Altered Gene Expression in Cerulein-Stimulated Pancreatic Acinar Cells: Pathologic Mechanism of Acute Pancreatitis

Acute pancreatitis is a multifactorial disease associated with the premature activation of digestive enzymes. The genes expressed in pancreatic acinar cells determine the severity of the disease. The present study determined the differentially expressed genes in pancreatic acinar cells treated with cerulein as an in vitro model of acute pancreatitis. Pancreatic acinar AR42J cells were stimulated with 10(-8) M cerulein for 4 h, and genes with altered expression were identified using a cDNA microarray for 4,000 rat genes and validated by real-time PCR. These genes showed a 2.5-fold or higher increase with cerulein: lithostatin, guanylate cyclase, myosin light chain kinase 2, cathepsin C, progestin-induced protein, and pancreatic trypsin 2. Stathin 1 and ribosomal protein S13 showed a 2.5-fold or higher decreases in expression. Real-time PCR analysis showed time-dependent alterations of these genes. Using commercially available antibodies specific for guanylate cyclase, myosin light chain kinase 2, and cathepsin C, a time-dependent increase in these proteins were observed by Western blotting. Thus, disturbances in proliferation, differentiation, cytoskeleton arrangement, enzyme activity, and secretion may be underlying mechanisms of acute pancreatitis.

Transmigração endotelial do fungo patogênico Sporothrix schenckii: modulação da via de p38MAPK/MLCK, Src e de moléculas de adesão celular / Endothelial transmigration of the pathogenic fungus, Sporothrix schenckii: pathway modulation of p38MAPK/MLCK, Src and cell adhesion molecules

Sporothrix schenckii é um fungo dimórfico, agente etiológico da esporotricose, uma micose subaguda ou crônica que pode eventualmente evoluir para complicações sistêmicas, principalmente em pacientes imunocomprometidos. O endotélio exerce um papel crucial durante infecções disseminadas já que, juntamente com as células epiteliais, representa uma barreira a ser ultrapassada por microorganismos invasores. Em estudos anteriores, observamos que S. schenckii transmigra preferencialmente pela rota paracelular (passagem entre células endoteliais adjacentes), interagindo em seguida com componenetes da matriz subendotelial. Também foram identificadas algumas vias de sinalização relacionadas à diferentes fases da interação de leveduras de S. schenckii com o endotélio in vitro (associação/endocitose, transmigração). No entanto, a correlação entre tais vias de sinalização e os mecanismos celulares da invasão do endotélio pelo fungo não foram efetivamente demonstrados. No presente trabalho, a análise do perfil de proteínas endoteliais totais fosforiladas em resíduos de tirosina mostrou que S. schenckii induz fosforilações em tempos curtos (< 15 minutos), em proteínas de massas moleculares 20, 13, 12 e 6KDa, enquanto alunas proteínas de mais alto peso molecular (83, 123, 136, 140 e 193 KDa) persistem fosforiladas em tempos mais longos durante a infecção (6 horas). As vias de transdução de sinais disparadas pela interação do fungo com o endotélio foram investigadas através do uso de inibidores da ativação de MAPKs p38 (SB 203580) e ERK (PD 98059), MLCK (W7) e de um quelante de Ca2+ intracelular (BAPTA). A transmigração de S. schenckii através de monocamadas de HUVECs por 6 horas mostrou ser dependente da ativação de ERK e p38, ions Ca2+ intracelular e MLCK. Estas vias estão também envolvidas nos rearranjos do citoesqueleto de actina que levam à contratilidade celular e aumento da permeabilidade endotelial. A interação do fungo com HUVECs induziu ativação de Src...

Sporothrix schenckii, a dimorphic fungus, is the causative agent of sporotrichosis, a cutaneous/subcutaneous mycosis which can eventually evolve to systemic complications, mainly in immunocompromised patients. The primary interaction of pathogenic fungi with endothelial cells (EC) is throught to be essential for the development of systemic infections. We have previously shown that S. schenckii cross endothelial monolayers through a paracellular pathway, in a process also modulated by the subendothelial matrix, and that the fungus is able to alter host signaling pathways. We observed that the interaction of S. schenckii with human umbilical vein endothelial cells (HUVECs) was regulated by tyrosine-phosphorylation of EC proteins. In the present work, we observed that S. schenckii stimulates the early increase (<15 minutes) in tyrosine-phorphorylation of 20, 13, 12 e 6 KDa endothelial proteins, whereas tyrosine-phosphorylation of higher molecular weight proteins (83, 123, 136, 140 e 193 KDa) persists up to 6 hours of endothelial infection. Selective signal transduction inhibitors (SB203580 and W7, for blocking p38 MAPK and MLCK activation, respectively) were able to inhibit transendothelial migration of S. schenckii. The process was also modulated by Ca++ions. These signaling pathways are crucial for the actin rearrangement associated to impairment of endothelial permeability. Long-term (3 hours) interaction of S. schenckii with HUVECs lead to increase of MLC2 phosphorylation and Src activation. Src was shown by others to be involved in the phosphorylation of VE-cadherin, thus provoking adherent junctions (AJs) disassembly. We found that S. schenckii induces tyrosine-phosphorylation of endothelial VE-cadherin up to 3 hours of interaction with endothelial cells. VE-cadherin phosphorylation can be triggered by the activation of E-selectin in endothelial cells. Since the time-course of the major signaling events correlated with the time needed...

The role of myosin light chain kinase in intestinal epithelial barrier dysfunction due to hypoxia / 中华烧伤杂志

<p><b>OBJECTIVE</b>To study the role of myosin light chain kinase (MLCK) in intestinal epithelial barrier dysfunction after hypoxia.</p><p><b>METHODS</b>The Caco-2 monolayers developed with Transwell inserts were exposed to hypoxia for 0 h (NC group), 2, 6, 8, 12 and 24 h (H group), and 6 h hypoxic specimens were treated with 100 mol/L ML-9 (T group). The transepithelial electrical resistance (TER) of monolayers was measured with an ohmmeter. The tight junction protein ZO-1 of monolayers was analyzed by immunofluorescence assay. The protein expressions of phosphorylated myosin light chain (p-MLC) and MLCK were detected by Western blotting.</p><p><b>RESULTS</b>The TER of monolayers in H group at 6, 8, 12 and 24 h was 422 +/- 17, 427 +/- 27, 403 +/- 40 and 426 +/- 22 ohms respectively, which was significantly lower than that of NC group (451 +/- 27 ohms, P < 0.05). The TER of monolayers in T group was 558 +/- 110 ohms, which was significantly higher than that in H group at each time point ( P < 0.01). The ZO-1 of monolayers in H group at 6 h was irregular in arrangement, with interruptions and rugae, and sawtooth. These abnormalities were ameliorated in T group (regular in arrangement, with little or without ruga and sawtooth). The protein expressions of p-MLC and MLCK in H group at each time point were higher than those in NC group.</p><p><b>CONCLUSIONS</b>Intestinal epithelial barrier dysfunction after hypoxia can be mediated by MLCK.</p>

Role of phosphatidylinositol 3-kinase and myosin light chain kinase during the activation of thrombin receptors / 中国实验血液学杂志

The objective of study was to compare the influences of wortmannin on platelet aggregation and platelet membrane surface glycoproteins GPIb expression after thrombin receptor activation, and to investigate the role of phosphatidylinositol 3-kinase (PI3-K) and myosin light chain kinase (MLCK) in the course of thrombin receptor activation. Peptide SFLLRN (PAR1-AP) and AYPGKF (PAR4-AP) were used for stimulating platelet, and the changes of platelet aggregation and GPIb were analyzed with 100 nmol/L wortmannin (inhibitor of PI3-K) and 10 micromol/L wortmannin (inhibitor of MLCK). The results indicated that the platelet activation was influenced by either concentration of wortmannin in response to PAR stimulation. Platelet aggregation was apparently inhibited by 10 micromol/L wortmannin through both PAR peptides, and was slightly inhibited by 100 nmol/L wortmannin only under PAR1-AP activation. In addition, GPIbalpha internalization was partly inhibited by 100 nmol/L wortmannin in response to PAR1 (p < 0.05 at 1, 2, 5 min) and PAR4 (p < 0.05 at 2, 5, 10 min) activation. Meanwhile, 10 micromol/L wortmannin induced little change for GPIbalpha centralisation in the course of PAR activation, with a delayed restoration of surface GPIbalpha observed under PAR1-AP activation, and no change of GPIbalpha redistribution existed under PAR4-AP activation. It is concluded that the different roles of PI3-K and MLCK exist in the course of thrombin receptor activation. PI3-K accelerates the short course of GPIb centralisation for two PAR signal pathways, while MLCK inhibits the restoration of GPIbalpha in PAR1 pathway.

Functional regulation of endothelial Myosin light chain kinase in extravascular migration of fibrosarcoma cells / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To evaluate the functional regulation of endothelial Myosin light chain kinase (MLCK) in extravascular migration of fibrosarcoma HT1080 cells.</p><p><b>METHODS</b>An in vitro model of fibrosarcoma cell transmigration across a monolayer of HUVEC cultured on collagen gel was applied to observe extravascular migration of HT1080 cells,and were the electrical resistance of HUVEC monolayer and endothelial MLC phosphorylation in extravascular migration of HT1080 cells.</p><p><b>RESULT</b>HT1080 cells migrated through endothelial cells into collagen gel, the electrical resistance of a HUVEC monolayer was reduced and endothelial MLC phosphorylation was enhanced in extravascular migration of fibrosarcoma cells. Endothelial MLCK inhibitor (ML-7) blocked extravascular migration of HT1080 cells and inhibited reduction of electrical resistance of a HUVEC monolayer and enhancement of endothelial MLC phosphorylation in extravascular migration of HT1080 cells in a dose-dependent manner.</p><p><b>CONCLUSION</b>Endothelial MLCK regulates fibrosarcoma cell transendothelial migration through MLC phosphorylation, leading to cytoskeletal reorganization and endothelial cell constriction, then fibrosarcoma cells migrate into extravascular tissue through the gaps between endothelial cells.</p>