[Protective effects of hydrogen sulfide on diaphragmatic muscle of Type 1 diabetic rats and its anti-apoptotic mechanisms].

OBJECTIVE: To explore the protective effects of hydrogen sulfide (H2S) on diaphragmatic muscle of Type 1 diabetic rats and its anti-apoptotic mechanism.
 METHODS: Thirty male Sprague Dawley rats were randomly divided into a control group, a diabetes group and a treatment group (n=10 per group). Streptozotocin (i.p.) was utilized to establish a rat model of Type 1 diabetes mellitus (DM). The DM rats were treated with NaHS solution (i.p.). After 8 weeks, the diaphragmatic muscle contractility was assessed by isolated diaphragmatic strips experiments. The peak twitch tension (Pt), maximum tetanic tension (Po), time to peak contraction (CT), half relaxation time (1/2RT) and maximal rates of contraction/relaxation (±dT/dtmax) were measured. The alterations of diaphragmtic ultrastructure were observed by electron microscopy. The content of malondialdehyde (MDA), the activities of superoxide dismutase (SOD) and caspase-3 were analyzed by spectrophotometric method. The expressions levels of Bcl-2 and Bax mRNA in diaphragmatic muscle were detected by RT-PCR.
 RESULTS: Compared with the control group, in the diabetic group, the Pt, Po and ±dT/dtmax were significantly reduced (all P<0.01), while CT and 1/2RT were significantly increased (both P<0.01); ultrastructure in the diaphragmatic muscle were obviously changed; the content of MDA and the activity of caspase-3 were increased (both P<0.01), while the activity of SOD was decreased (P<0.01); the ratio of Bcl-2/Bax at mRNA level was decreased (P<0.01). Compared with the diabetes group, in the treatment group, the diaphragm contractility and ultrastructural damage were improved; the content of MDA and the activity of caspase-3 were decreased (P<0.05, P<0.01 respectively), while the activity of SOD was increased (P<0.01), the ratio of Bcl-2/Bax at mRNA level was also increased (P<0.01). 
 CONCLUSION: The exogenous H2S can protect diaphragmatic muscle of Type 1 diabetic rats, which is related to reducing oxidative damage and suppressing cell apoptosis.

Negative modulation of NO for diaphragmatic contractile reduction induced by sepsis and restraint position.

In practice of forensic medicine, potential disease can be associated with fatal asphyxia in restraint position. Research has demonstrated that nitric oxide (NO) and nitric oxide synthase (NOS) are plentifully distributed in skeletal muscle, contributing to the regulation of contractile and relaxation. In the current study, respiratory functions, indices of diaphragmatic biomechanical functions ex vivo, as well as NO levels in serum, the expressions of diaphragmatic inducible NOS (iNOS) mRNA, and the effects of L-NNA on contractility of the diaphragm were observed in sepsis induced by cecal ligation and puncture (CLP) under the condition of restraint position. The results showed that in the CLP12-18h rats, respiratory dysfunctions; indices of diaphragmatic biomechanical functions (Pt, +dT/dt(max), -dT/dt(max), CT, Po, force over the full range of the force-frequency relationship and fatigue resistance) declined progressively; the NO level in serum, and iNOS mRNA expression in the diaphragm increased progressively; force increased significantly at all stimulation frequencies after L-NNA pre-incubation. Restraint position 1 h in CLP12 h rats resulted in severe respiratory dysfunctions after relative stable respiratory functions, almost all the indices of diaphragmatic biomechanical functions declined further, whereas little change took place in NO level in serum and diaphragmatic iNOS mRNA expression; and the effects of L-NNA were lack of statistical significance compared with those of CLP12 h, but differed from CLP18 h group. These results suggest that restraint position and sepsis act together in a synergistic manner to aggravate the great reduction of diaphragmatic contractility via, at least in part, the negative modulation of NO, which may contribute to the pathogenesis of positional asphyxia.

Calcium activated potassium channel and protein kinase C participate in the cardiac protection of remote post conditioning.

The present study was designed to investigate the roles of Ca(2+) activated K(+) channel (KCa) and protein kinase C (PKC) in the protective mechanisms of remote ischemic post conditioning (RPostC) when rat heart was subjected to ischemia/reperfusion (I/R) injury in vivo. Rat heart was subjected to regional ischemia for 45 min and reperfusion for 180 min in vivo to mimic I/R injury. RPostC was induced by 5 min right femoral artery occlusion followed by 5 min reperfusion for 3 cycles (totally 30 min) after 15 min of cardiac ischemia. Delayed remote ischemic post conditioning (delayed RPostC) was induced after 10 min of cardiac reperfusion. The hemodynamic parameters including mean arterial blood pressure and heart rate (HR) were recorded, and lactate dehydrogenase (LDH) release in plasma and infarct size were determined, and arrhythmia scores were calculated. In contrast to I/R, RPostC reduced infarct size and LDH release during reperfusion, the occurrence of arrhythmia was decreased, but no changes in delayed RPostC. The specific inhibitor of KCa iberiotoxin and PKC inhibitor chelerythrine both attenuated the role of RPostC. The findings indicated that RPostC had a protective effect on myocardial ischemia/reperfusion injury. Opening of KCa and activating of PKC may be involved in the mechanisms of RPostC.

[Effects of restraint position on changes of diaphragmatic mechanical characteristic in rats].

OBJECTIVE: To observe effects of restraint position on the changes of diaphragmatic mechanical characteristic in rats, and try to explore the role of nitric oxide (NO). METHODS: Rat model of restraint position was established. Rats were divided into control group, restraint position 12h and 24h groups. The markers of respiratory functions in vivo and the biomechanical markers of diaphragmatic characteristic ex vivo were evaluated. Serum NO levels were measured with spectrophotometry. The expressions of nNOS and iNOS mRNA in diaphragm were detected using RT-PCR. RESULTS: Compared with control group, respiratory rate, tidal volume and minute ventilation were significantly decreased in the restraint position 12h and 24h groups. Pt of diaphragm significantly decreased and force-generating capacity reduced at low frequency stimulation in 12h group. Force-generating capacity over the full range reduced at low and high frequency stimulation in 24h group. Pt of diaphragm in control and restraint position groups increased after L-NNA pre-incubation. Force-frequency relationship after L-NNA pre-incubation reduced in 24h group. NO level in serum increased significantly in the restraint position groups. Diaphragmatic nNOS mRNA expression was upregulated significantly in the restraint position groups. CONCLUSION: Restraint position induces the decreasement of diaphragmatic contractility and the decreasement is mediated by NO from diaphragm or circulation blood.

Ca2+ and acidosis synergistically lead to the dysfunction of cortical GABAergic neurons during ischemia.

Cell death in cerebral ischemia is presumably initiated by neural excitotoxicity resulted from the dysfunction of inhibitory neurons in early stage. Molecular processes underlying the ischemic injury of inhibitory neurons remain to be elusive, which we investigated by biochemical manipulations with cellular imaging and patch clamp at GFP-labeled GABAergic cells in cortical slices. Ischemia induces Ca(2+) elevation, acidosis and dysfunction in GABAergic cells. An elevation of cytoplasmic Ca(2+) or H(+) impairs the encoding of action potentials in these neurons. The effects of Ca(2+) and H(+) are additive in nature and occlude ischemic outcomes. Ischemia impairs spike production through prolonging spike refractory periods and raising threshold potentials. Therefore, calcium toxicity and acidosis during ischemia synergistically impair the dynamics of sodium channels and function of cortical GABAergic neurons, which lead to neural excitotoxicity. Our results also suggest that the cocktail therapeutics is needed to prevent neuronal death from ischemia.

[Activation of mitochondrial aldehyde dehydrogenase 2 and inhibition of mitochondrial permeability transition pore involved in cardioprotection of ethanol postconditioning].

OBJECTIVE: To investigate whether activation of mitochondrial aldehyde dehydrogenase 2 (ALDH2) and inhibition of mitochondrial permeability transition pore (mitoPTP) were involved in the cardioprotection of ethanol postconditioning in isolated rat heart. METHODS: Hearts isolated from male Sprague-Dawley rats were perfused on a langendorff apparatus and subjected to 30 min of regional ischemia (occlusion of left anterior descending artery) followed by 120 min of reperfusion. The ventricular hemodynamic parameters and lactate dehydrogenase (LDH) release during reperfusion were measured. Infarct size was measured by TTC staining method and the expression of ALDH2 at mRNA level of left anterior myocardium was detected by RT-PCR. RESULT: In contrast to ischemia and reperfusion, ethanol postconditioning improved the recovery of left ventricular developed pressure, maximal rise/fall rate of left ventricular pressure during reperfusion, reduced LDH release and infarct size. The expression of ALDH2 mRNA level was increased. Administration of mitoPTP activator atractyloside attenuated the effect of ethanol postconditioning, LDH release and infarct size were increased, and the recovery of hemodynamic parameters was inhibited. The expression of ALDH2 mRNA was decreased. CONCLUSION: Ethanol postconditioning has cardioprotection effect, which may be associated with upregulating mitochondrial ALDH2 mRNA expression and inhibiting the opening of mitochondrial permeability transition pore.

The postnatal development of intrinsic properties and spike encoding at cortical GABAergic neurons.

GABAergic neurons play a critical role in maintaining the homeostasis of brain functions for well-organized behaviors. It is not known about the dynamical change in signal encoding at these neurons during postnatal development. We investigated this issue at GFP-labeled GABAergic neurons by whole-cell recording in cortical slices of mice. Our results show that the ability of spike encoding at GABAergic neurons is improved during postnatal development. This change is associated with the reduction of refractory periods and threshold potentials of sequential spikes, as well as the improvement of linear correlations between intrinsic properties and spike capacity. Therefore, the postnatal maturation of the spike encoding capacity at GABAergic neurons will stabilize the excitatory state of cerebral cortex.

Intracellular Ca2+ regulates spike encoding at cortical GABAergic neurons and cerebellar Purkinje cells differently.

Spike encoding at GABAergic neurons plays an important role in maintaining the homeostasis of brain functions for well-organized behaviors. The rise of intracellular Ca2+ in GABAergic neurons causes synaptic plasticity. It is not clear how intracellular Ca2+ influences their spike encoding. We have investigated this issue at GFP-labeled GABAergic cortical neurons and cerebellar Purkinje cells by whole-cell recording in mouse brain slices. Our results show that an elevation of intracellular Ca2+ by infusing adenophostin-A lowers spike encoding at GABAergic cortical neurons and enhances encoding ability at cerebellar Purkinje cells. These differential effects of cytoplasmic Ca2+ on spike encoding are mechanistically associated with Ca2+-induced changes in the refractory periods and threshold potentials of sequential spikes, as well as with various expression ratios of CaM-KII to calcineurin in GABAergic cortical neurons and cerebellar Purkinje cells.

Ischemia deteriorates the spike encoding of rat cerebellar Purkinje cells by raising intracellular Ca2+.

Ischemia-induced excitotoxicity at cerebellar Purkinje cells is presumably due to a persistent glutamate action. To the fact that they are more vulnerable to ischemia than other glutamate-innervated neurons, we studied whether additional mechanisms are present and whether cytoplasm Ca(2+) plays a key role in their ischemic excitotoxicity. Ischemic changes in the excitability of Purkinje cells were measured by whole-cell recording in cerebellar slices of rats with less glutamate action. The role of cytoplasm Ca(2+) was examined by two-photon cellular imaging and BAPTA infusion in Purkinje cells. Lowering perfusion rate to cerebellar slices deteriorated spike timing and raised spike capacity of Purkinje cells. These changes were associated with the reduction of spike refractory periods and threshold potentials, as well as the loss of their control to spike encoding. Ischemia-induced functional deterioration at Purkinje neurons was accompanied by cytoplasm Ca(2+) rise and prevented by BAPTA infusion. Therefore, the ischemia destabilizes the spike encoding of Purkinje cells via raising cytoplasm Ca(2+) without a need for glutamate, which subsequently causes their excitotoxic death.

PKC and CaMK-II inhibitions coordinately rescue ischemia-induced GABAergic neuron dysfunction.

Cerebral ischemia leads to neuronal death for stroke, in which the imbalance between glutamatergic neurons and GABAergic neurons toward neural excitotoxicity is presumably involved. GABAergic neurons are vulnerable to pathological factors and impaired in an early stage of ischemia. The rescue of GABAergic neurons is expected to be the strategy to reserve ischemic neuronal impairment. As protein kinase C (PKC) and calmodulin-dependent protein kinase II (CaMK-II) are activated during ischemia, we have investigated whether the inhibitions of these kinases rescue the ischemic impairment of cortical GABAergic neurons. The functions of GABAergic neurons were analyzed by whole-cell recording in the cortical slices during ischemia and in presence of 1-[N,O-bis(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazine (CaMK-II inhibitor) and chelerythrine chloride (PKC inhibitor). Our results indicate that PKC inhibitor or CaMK-II inhibitor partially prevents ischemia-induced functional deficits of cortical GABAergic neurons. Moreover, the combination of PKC and CaMK-II inhibitors synergistically reverses this ischemia-induced deficit of GABAergic neurons. One of potential therapeutic strategies for ischemic stroke may be to rescue the ischemia-induced deficit of cortical GABAergic neurons by inhibiting PKC and CaMK-II.

Coordinated Plasticity among Glutamatergic and GABAergic Neurons and Synapses in the Barrel Cortex Is Correlated to Learning Efficiency.

Functional plasticity at cortical synapses and neurons is presumably associated with learning and memory. Additionally, coordinated refinement between glutamatergic and GABAergic neurons occurs in associative memory. If these assumptions are present, neuronal plasticity strength and learning efficiency should be correlated. We have examined whether neuronal plasticity strength and learning efficiency are quantitatively correlated in a mouse model of associative learning. Paired whisker and odor stimulations in mice induce odorant-induced whisker motions. The fully establishment of this associative memory appears fast and slow, which are termed as high learning efficiency and low learning efficiency, respectively. In the study of cellular mechanisms underlying this differential learning efficiency, we have compared the strength of neuronal plasticity in the barrel cortices that store associative signals from the mice with high vs. low learning efficiencies. Our results indicate that the levels of learning efficiency are linearly correlated with the upregulated strengths of excitatory synaptic transmission on glutamatergic neurons and their excitability, as well as the downregulated strengths of GABAergic neurons' excitability, their excitatory synaptic inputs and inhibitory synaptic outputs in layers II~III of barrel cortices. The correlations between learning efficiency in associative memory formation and coordinated plasticity at cortical glutamatergic and GABAergic neurons support the notion that the plasticity of associative memory cells is a basis for memory strength.

Activity strengths of cortical glutamatergic and GABAergic neurons are correlated with transgenerational inheritance of learning ability.

The capabilities of learning and memory in parents are presumably transmitted to their offsprings, in which genetic codes and epigenetic regulations are thought as molecular bases. As neural plasticity occurs during memory formation as cellular mechanism, we aim to examine the correlation of activity strengths at cortical glutamatergic and GABAergic neurons to the transgenerational inheritance of learning ability. In a mouse model of associative learning, paired whisker and odor stimulations led to odorant-induced whisker motion, whose onset appeared fast (high learning efficiency, HLE) or slow (low learning efficiency, LLE). HLE male and female mice, HLE female and LLE male mice as well as HLE male and LLE female mice were cross-mated to have their first generation of offsprings, filials (F1). The onset of odorant-induced whisker motion appeared a sequence of high-to-low efficiency in three groups of F1 mice that were from HLE male and female mice, HLE female and LLE male mice as well as HLE male and LLE female mice. Activities related to glutamatergic neurons in barrel cortices appeared a sequence of high-to-low strength in these F1 mice from HLE male and female mice, HLE female and LLE male mice as well as HLE male and LLE female mice. Activities related to GABAergic neurons in barrel cortices appeared a sequence of low-to-high strength in these F1 mice from HLE male and female mice, HLE female and LLE male mice as well as HLE male and LLE female mice. Neuronal activity strength was linearly correlated to learning efficiency among three groups. Thus, the coordinated activities at glutamatergic and GABAergic neurons may constitute the cellular basis for the transgenerational inheritance of learning ability.

The postnatal development of refractory periods and threshold potentials at cerebellar Purkinje neurons.

Cerebellum is involved in the motion coordination and working memory, to which spike programming at Purkinje neurons are essential. The development of Purkinje neurons in the embryonic stage has been well studied. However, it is not clear about the maturation of their intrinsic property related to spike programming during postnatal period. We developed the approach to quantify the intrinsic property of sequential spikes with whole-cell recording, and analyzed the postnatal development of Purkinje neurons in cerebellar slices. Our results demonstrate that the threshold potentials shift toward more negatively than resting membrane potential, refractory periods following each of spikes decrease, as well as the relationship between refractory periods and inter-spike intervals converts to be more linear during the postnatal maturation. This postnatal plasticity of neuronal intrinsic properties enhances the firing ability and spike capacity, in turn strengthens spike programming, at cerebellar Purkinje neurons.

Associations of Unilateral Whisker and Olfactory Signals Induce Synapse Formation and Memory Cell Recruitment in Bilateral Barrel Cortices: Cellular Mechanism for Unilateral Training Toward Bilateral Memory.

Somatosensory signals and operative skills learned by unilateral limbs can be retrieved bilaterally. In terms of cellular mechanism underlying this unilateral learning toward bilateral memory, we hypothesized that associative memory cells in bilateral cortices and synapse innervations between them were produced. In the examination of this hypothesis, we have observed that paired unilateral whisker and odor stimulations led to odorant-induced whisker motions in bilateral sides, which were attenuated by inhibiting the activity of barrel cortices. In the mice that showed bilateral cross-modal responses, the neurons in both sides of barrel cortices became to encode this new odor signal alongside the innate whisker signal. Axon projections and synapse formations from the barrel cortex, which was co-activated with the piriform cortex, toward its contralateral barrel cortex (CBC) were upregulated. Glutamatergic synaptic transmission in bilateral barrel cortices was upregulated and GABAergic synaptic transmission was downregulated. The associative activations of the sensory cortices facilitate new axon projection, glutamatergic synapse formation and GABAergic synapse downregulation, which drive the neurons to be recruited as associative memory cells in the bilateral cortices. Our data reveal the productions of associative memory cells and synapse innervations in bilateral sensory cortices for unilateral training toward bilateral memory.

Activation of ALDH2 with Low Concentration of Ethanol Attenuates Myocardial Ischemia/Reperfusion Injury in Diabetes Rat Model.

The aim of this paper is to observe the change of mitochondrial aldehyde dehydrogenase 2 (ALDH2) when diabetes mellitus (DM) rat heart was subjected to ischemia/reperfusion (I/R) intervention and analyze its underlying mechanisms. DM rat hearts were subjected to 30 min regional ischemia and 120 min reperfusion in vitro and pretreated with ALDH2 activator ethanol (EtOH); cardiomyocyte in high glucose (HG) condition was pretreated with ALDH2 activator Alda-1. In control I/R group, myocardial tissue structure collapse appeared. Compared with control I/R group, left ventricular parameters, SOD activity, the level of Bcl-2/Bax mRNA, ALDH2 mRNA, and protein expressions were decreased and LDH and MDA contents were increased, meanwhile the aggravation of myocardial structure injury in DM I/R group. When DM I/R rats were pretreated with EtOH, left ventricular parameters, SOD, Bcl-2/Bax, and ALDH2 expression were increased; LDH, MDA, and myocardial structure injury were attenuated. Compared with DM + EtOH I/R group, cyanamide (ALDH2 nonspecific blocker), atractyloside (mitoPTP opener), and wortmannin (PI3K inhibitor) groups all decreased left ventricular parameters, SOD, Bcl-2/Bax, and ALDH2 and increased LDH, MDA, and myocardial injury. When cardiomyocyte was under HG condition, CCK-8 activity and ALDH2 protein expression were decreased. Alda-1 increased CCK-8 and ALDH2. Our findings suggested enhanced ALDH2 expression in diabetic I/R rats played the cardioprotective role, maybe through activating PI3K and inhibiting mitoPTP opening.

Acidosis-Induced Dysfunction of Cortical GABAergic Neurons through Astrocyte-Related Excitotoxicity.

BACKGROUND: Acidosis impairs cognitions and behaviors presumably by acidification-induced changes in neuronal metabolism. Cortical GABAergic neurons are vulnerable to pathological factors and their injury leads to brain dysfunction. How acidosis induces GABAergic neuron injury remains elusive. As the glia cells and neurons interact each other, we intend to examine the role of the astrocytes in acidosis-induced GABAergic neuron injury. RESULTS: Experiments were done at GABAergic cells and astrocytes in mouse cortical slices. To identify astrocytic involvement in acidosis-induced impairment, we induced the acidification in single GABAergic neuron by infusing proton intracellularly or in both neurons and astrocytes by using proton extracellularly. Compared the effects of intracellular acidification and extracellular acidification on GABAergic neurons, we found that their active intrinsic properties and synaptic outputs appeared more severely impaired in extracellular acidosis than intracellular acidosis. Meanwhile, extracellular acidosis deteriorated glutamate transporter currents on the astrocytes and upregulated excitatory synaptic transmission on the GABAergic neurons. Moreover, the antagonists of glutamate NMDA-/AMPA-receptors partially reverse extracellular acidosis-induced injury in the GABAergic neurons. CONCLUSION: Our studies suggest that acidosis leads to the dysfunction of cortical GABAergic neurons by astrocyte-mediated excitotoxicity, in addition to their metabolic changes as indicated previously.

[Effect of soybean isoflavones on heart function of rats with adriamycin-induced heart failure].

OBJECTIVE: To observe the protective effect of soybean isoflavones (SI) on the heart function of the rats with adriamycin induced heart failure. METHODS: Thirty adult male SD rats were divided into 5 groups:normal control (NC) group, adriamycin (ADR) group, L-SI group, M-SI group and H-SI group. SI of 30, 60, 120 mg.kg(-1).d(-1) was orally administered through a stomach tube once a day for 6 days in L-SI group, M-SI group and H-SI group, respectively. The other two groups were given the same amount of normal saline the same way. Then ADR of 10 mg/kg was given intraperitoneally once to copy the model of heart-failure. The MedLab-U/4c biological signal collecting system was used to record and analyze the LVSP of the rats. The pathological changes of the cardiomyocytes were observed. RESULTS: As compared with NC group, the LVSP,+/-dp/dt max, Vpm of the ADR group were significantly lower (P<0.05 or P<0.01), but those of the H-SI group were markedly higher than those of the ADR group (P<0.01). Electron microscopic morphometry of the heart samples of the rats in ADR group revealed typical alterations, consisting an increase of collagen content, vacuolation, diminishing of the cardiomyocyte diameter, alteration of myofilaments and Z-lines of myofibers, and myofibrillar degeneration. SI of 120 mg.kg(-1).d(-1) treatment could prevent the loss of myofibrillae and the reduction of myocyte diameter, and the degeneration of myofilaments and Z-lines were reversed by SI. CONCLUSION: SI of 120 mg.kg(-1).d(-1) treatment can relieve the toxic effect of ADR on myocardium, and also obviously improve the cardiac contractility of heart-failure rats.

Effect of Shengmai injection () on diaphragmatic contractility in doxorubicin-treated rats.

OBJECTIVE: To explore the diaphragmatic toxicity in doxorubicin (DOX)-treated rats and the related mechanisms, as well as the effects of Shengmai Injection (SMI, ) on the diaphragmatic dysfunction. METHODS: Thirty Sprague-Dawley male rats were randomly divided into three groups: control, DOX-treated and DOX+SMI treated groups. DOX was given to rats in DOX and DOX+SMI groups in 6 equal doses [2.5 mg/kg, intraperitoneal injection (i.p.)], on alternate days, over a period of 2 weeks for a cumulative dose of 15 mg/kg. SMI was given to DOX+SMI rats in 12 doses (3 mL/kg, i.p.) for a period of 2 weeks before the administration of DOX and 2 weeks during the administration of DOX. The rats in the control group received equal volume of normal saline. Subsequently, the twitch and tetanic characteristics and force-frequency relationships, and the malondialdehyde (MDA) levels and the superoxide dismutase (SOD) activities, as well as the mRNA content and proteins of inducible nitric oxide synthase (iNOS) were determined. RESULTS: The DOX-treated rats had decreased the peak twitch tension (Pt), maximal tetanic tension (P0) and force-frequency relationship as compared with the control rats (P<0.01), while the diaphragm contractility in rats treated with SMI were significantly higher than that in DOX-treated rats (P<0.01). The DOX-treated rats had increased MAD levels and decreased SOD activities (P<0.05), and SMI decreased the MDA levels and increased the SOD activities in DOX-treated rats (P<0.05). Ultrastructure of diaphragm in the DOX-treated rats revealed typical alterations including fracture of diaphragm fibers, and edema and degeneration of mitochondria; these changes were relieved by SMI treatment. The mRNA content and protein of iNOS in DOX-treated rats were remarkably higher than those in control rats (P<0.01), while SMI decreased the mRNA expression level of iNOS in DOX-treated rats (P<0.05). CONCLUSIONS: Lipid peroxidation is responsible for DOX-induced diaphragm toxicity. SMI protects diaphragm muscles and their function from DOX impairment, and these beneficial effects may be somehow correlated with the decrease in expression of iNOS and lipid peroxidation.

Remote ischemic postconditioning protects the heart by upregulating ALDH2 expression levels through the PI3K/Akt signaling pathway.

Remote ischemic postconditioning (RIPostC) has been demonstrated to protect the myocardium against ischemia/reperfusion (I/R) injury; however, the mediator and underlying mechanisms remain to be elucidated. It has been confirmed that aldehyde dehydrogenase 2 (ALDH2) is involved in the remote ischemic preconditioning pathway, but whether it is involved in RIPostC remains unknown. The aim of the present study was to determine whether increased ALDH2 expression levels were involved in the cardioprotective effect evoked by RIPostC via the phosphatidylinositol­3­kinase (PI3K)/Akt signaling pathway. Male Sprague Dawley rats (n=48) were randomly allocated into the following four groups: Sham group, I/R group, RIPostC group, and RIPostC plus wortmannin group (RIPostC+Wort). With the exception of the Sham group, the anesthetized rats underwent 45 min of coronary artery occlusion followed by 180 min of reperfusion to mimic an I/R injury model. Hemodynamic parameters, including the mean arterial pressure and heart rate, were recorded, the infarct size was determined and the plasma lactate dehydrogenase (LDH) content and creatine kinase (CK) activity levels were measured. The expression levels of Bcl­2 and Bax at the mRNA level and ALDH2, Akt, phospho­Akt (p­Akt), caspase­3 and cleaved caspase­3 at the protein level in the left anterior myocardium were assessed. In the RIPostC group, the infarct size was reduced versus that of the I/R group. The plasma LDH content and CK activity levels were also reduced. The expression levels of ALDH2 protein were elevated, accompanied with increases in the levels of Bcl­2/Bax and p­Akt/Akt and a reduction in the levels of cleaved caspase­3. When the PI3K inhibitor wortmannin was administered at reperfusion, the p­Akt/Akt ratio was markedly reduced and associated with a reduction in the ALDH2 and Bcl­2/Bax levels, and the cleaved caspase­3 expression levels were elevated. In conclusion, ALDH2 may be an important mediator in the cardioprotection of RIPostC through the PI3K/Akt­dependent signaling pathway.

[Diaphragm dysfunction and expressions of calcium regulatory proteins in diabetic rats].

OBJECTIVE: To study the changes in diaphragmatic function and gene expressions of calcium regulatory proteins in diabetic rats and explore the mechanism of diaphragm dysfunction in diabetes mellitus. METHODS: SD rats were randomly divided into normal control group and diabetic (induced by intraperitoneal STZ injection) group. After 4 and 8 weeks, the body weight and diaphragm to body weight ratio were measured, and the activities of succinic dehydrogenase (SDH) in the diaphragm and blood glucose were assayed. The diaphragm contractility was assessed and the alterations of diaphragm ultrastructure were observed. RT-PCR was used to detect the changes in sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) and phospholamban (PLB) mRNA expressions in the diaphragm. RESULTS: The diabetic rats showed a significant weight loss with a lowered diaphragm to body weight ratio (P<0.01) and SDH activity (P<0.01). The peak twitch tension and maximum tetanic tension of the diaphragm were significantly lowered and the time to peak contraction and half relaxation time significantly prolonged (P<0.01) in the diabetic rats, which also exhibited a lowered tetanic force in response to stimulus (P<0.01). Transmission electron microscopy revealed obvious ultrastructural changes of the diaphragm in diabetic rats. RT-PCR showed significantly decreased SERCA and increased PLB mRNA expressions in diabetic rat diaphragm (P<0.01), and these changes intensified with time (P<0.01). CONCLUSION: Diabetes can cause impairment of diaphragmatic ultrastructure, mitochondrial injuries, and lowered SDH activity and ATP production. Decreased SERCA and increased PLB mRNA expressions in diabetes result in reduced Ca(2+) uptake by the diaphragm sarcoplasmic reticulum to induce diaphragm dysfunction.