Objective:To evaluate the role of silent information regulator sirtuin 1 (SIRT1) in mitochondrial dysfunction in mice with lipopolysaccharide (LPS)-induced brain injury.Methods:Eighty clean-grade male C57BL/6 mice, aged 6-8 weeks, were divided into 4 groups ( n=20 each) by the random number table method: control group (group C), LPS-induced brain injury group (LPS group), LPS-induced brain injury plus SIRT1 inhibitor EX527 group (LPS+ E group), and LPS-induced brain injury plus SIRT1 agonist SRT1720 group (LPS+ S group). Brain injury was induced by intravenous injection of LPS 10 mg/kg. EX527 10 mg/kg was intraperitoneally injected at 72 h before LPS injection in group LPS+ E, and the equal volume of dimethyl sulfoxide was intraperitoneally injected instead in the other three groups. SRT1720 100 mg/kg was intraperitoneally injected at 30 min before LPS injection in group LPS+ S, and the equal volume of dimethyl sulfoxide was intraperitoneally injected instead in the other three groups. The novel object recognition test was performed at 24 h after LPS injection, then the mice were sacrificed, and hippocampal tissues were harvested for determination of the number of the normal neurons in the hippocampal CA1 area, ATP content and activities of mitochondrial respiratory chain complexes Ⅰ, Ⅱ, Ⅲ and Ⅳ (by spectrophotometry), and mitochondrial membrane potential (MMP) (by Jc-1 staining) and for microscopic examination of pathological changes (by Nissl staining) and ultrastructure of neuronal mitochondria (with a transmission electron microscope). Results:Compared with group C, the preference index in novel object recognition, normal neuron count, activities of mitochondrial respiratory chain complexes Ⅰ, Ⅱ, Ⅲ and Ⅳ, MMP and ATP content were significantly decreased ( P<0.05), damage to hippocampal neurons was found, mitochondrial swelling was observed and cristae structure ruptured in LPS, LPS+ S and LPS+ E groups. Compared with group LPS, the preference index in novel object recognition, activities of mitochondrial respiratory chain complexes, MMP and ATP content were significantly decreased ( P<0.05), neuronal damage was aggravated, the mitochondrial swelling and fracture of crista structure were accentuated in group LPS+ E; the preference index in novel object recognition, activities of mitochondrial respiratory chain complexes, MMP and ATP content were significantly increased ( P<0.05), neuronal damage was alleviated, and the mitochondrial swelling and fracture of crista structure were ameliorated in group LPS+ S. Conclusions:Activation of SIRT1 can improve mitochondrial dysfunction and alleviate LPS-induced brain injury in mice.

Objective:To investigate the effect of electroacupuncture on calcium homeostasis in hippocampal neurons of mice with sepsis-associated encephalopathy (SAE).Methods:Twenty-four healthy male C57BL/6J mice, weighing 18-22 g, were divided into 4 groups ( n=6 each) using a random number table method: sham operation group (Sham group), SAE group, SAE plus electroacupuncture group (SAE+ EA group), and SAE plus sham electroacupuncture group (SAE+ SEA group). The virus carrying calcium ion (Ca 2+ ) fluorescent probes was injected and then an optical fiber was implanted into the hippocampal CA1 area to record the fluorescence signals of Ca 2+ . SAE was induced by cecal ligation and puncture in anesthetized mice at 3 weeks after administration. Starting from 3 days before surgery, Baihui and bilateral Quchi and bilateral Zusanli acupoints were stimulated for 30 min per day for 7 consecutive days in SAE+ EA group. In SAE+ SEA group, electroacupuncture was performed at the points 0.2 mm lateral to the corresponding acupoints without electrical stimulation. Open field tests were conducted at 5 days after surgery to record the number of rearing and changes in related Ca 2+ signals in hippocampal CA1 neurons. Novel object recognition tests were conducted at 6-7 days after surgery to record the recognition time and changes in related Ca 2+ signals in hippocampal CA1 neurons. Mice were sacrificed after the end of behavioral testing on 7 days after surgery, and brain tissues ipsilateral to the optical fiber implant were obtained and the fluorescence intensity of Ca 2+ in the hippocampal CA1 neurons was acquired using a fluorescent microscope. Results:Compared with Sham group, the number of rearing and amplitudes of related Ca 2+ signals in hippocampal CA1 neurons while rearing were significantly decreased in SAE group and SAE+ SEA group ( P<0.05), and no statistically significant changes were found in the parameters mentioned above in SAE+ EA group ( P>0.05), and the recognition index and amplitudes of related Ca 2+ signals while recognizing were significantly deceased, and the fluorescence intensity of Ca 2+ in hippocampal CA1 neurons was increased in SAE, SAE+ EA and SAE+ SEA groups ( P<0.05). Compared with SAE group and SAE+ SEA group, the number of rearing and amplitudes of related Ca 2+ signals in hippocampal CA1 neurons while rearing were significantly increased, the recognition index and amplitudes of related Ca 2+ signals in hippocampal CA1 neurons while recognizing were increased, and the fluorescence intensity of Ca 2+ in hippocampal CA1 neurons was decreased in SAE+ EA group ( P<0.05). There were no statistically significant differences in the parameters mentioned above between SAE group and SAE+ SEA group ( P>0.05). Conclusions:The mechanism by which electroacupuncture alleviates SAE may be related to regulation of Ca 2+ homeostasis in hippocampal neurons of mice.

Objective:To evaluate the role of small ubiquitin-associated modifier (SUMO) E3 ligase (PIAS)-regulated SUMOylation of peroxisome proliferator-activated receptor γ (PPARγ) in the endogenous protective mechanism against endotoxin-induced acute lung injury (ALI) in mice.Methods:Experiment Ⅰ Twenty-four clean-grade wild type male C57BL/6 mice, aged 6-8 weeks, weighing 18-22 g, were divided into 4 groups ( n=6 each) using a random number table method: control group (C group), ALI group, ALI+ PPARγ inducer TZD group (ALI+ T group) and ALI+ TZD+ SUMOylation inhibitor anacardic acid group (ALI+ T+ A group). Lipopolysaccharide (LPS) 15 mg/kg was injected into the tail vein to develop the ALI model. In ALI+ T+ A group, anacardic acid 5 mg/kg was intraperitoneally injected at 1 h before LPS administration. In ALI+ T group and ALI+ T+ A group, TZD 50 mg/kg was intraperitoneally injected at 30 min before LPS administration. The mice were sacrificed at 12 h after LPS administration, and the lung tissues were obtained to examine the pathological changes which were scored and to determine the wet/dry (W/D) weight ratio, and expression of PIAS1, PIAS2, PIAS3 and PIASy protein and mRNA (by Western blot or polymerase chain reaction). Experiment Ⅱ Mouse alveolar macrophages (MH-S cells) were cultured in vitro and divided into 4 groups ( n=5 each) using a random number table method: control group (C group), LPS group, LPS+ PIAS2 siRNA group (L+ P group) and LPS+ Con siRNA group (L+ C group). Cells were routinely cultured in group C. Cells were stimulated with 10 μg/ml LPS to develop the model of endotoxin challenge. PIAS2 siRNA 50 nmol/L and Con siRNA 50 nmol/L were transfected at 48 h before LPS was added in L+ P group and L+ C group, respectively. The cells were collected at 24 h of incubation with LPS to determine the cell viability, levels of M1 and M2 alveolar macrophages (by flow cytometry), expression of PIAS2 and PPARγ (by Western blot), co-expression of PPARγ-SUMO1 (by immunoprecipitation) and expression of tumor necrosis factor-alpha (TNF-α) and interleukin-10 (IL-10) mRNA (by polymerase chain reaction). The ratio of M1/M2 was calculated. Results:Experiment Ⅰ Compared with C group, the lung injury scores and W/D ratio were significantly increased, and the expression of PIAS2 protein and mRNA was up-regulated in the other three groups ( P<0.05). Compared with ALI group, the lung injury scores and W/D ratio were significantly decreased, and the expression of PIAS2 protein and mRNA was up-regulated in ALI+ T group and ALI+ T+ A group ( P<0.05). Compared with ALI+ T group, the lung injury scores and W/D ratio were significantly increased, and the expression of PIAS2 protein and mRNA was down-regulated in ALI+ T+ A group ( P<0.05). There was no significant difference in the expression of PIAS1, PIAS3 and PIASy protein and mRNA in lung tissues among the four groups ( P>0.05). Experiment Ⅱ Compared with C group, the cell viability was significantly decreased, the expression of PPARγ and co-expression of PPARγ-SUMO1 was up-regulated, the levels of M1 and M2 macrophages and M1/M2 ratio were increased, the expression of TNF-α mRNA was up-regulated, and the expression of IL-10 mRNA was down-regulated in the other three groups, and PIAS2 expression was significantly up-regulated in L group and L+ C group ( P<0.05). Compared with L group, the cell viability was significantly decreased, the expression of PIAS2 and PPARγ and PPARγ-SUMO1 co-expression were down-regulated, the M1 macrophage level and M1/M2 ratio were increased, TNF-α mRNA expression was up-regulated, and the expression of IL-10 mRNA was down-regulated in L+ P group ( P<0.05), and no significant change was found in the parameters mentioned above in L+ C group ( P>0.05). Compared with L+ C group, the cell viability was significantly decreased, the expression of PIAS2 and PPARγ and co-expression of PPARγ-SUMO1 were down-regulated, the level of M1 alveolar macrophages and M1/M2 ratio were increased, the expression of TNF-α mRNA was down-regulated, and the expression of IL-10 mRNA was up-regulated in L+ P group ( P<0.05). Conclusions:PIAS2-regulated SUMOylation of PPARγ is the endogenous protective mechanism against endotoxin-induced ALI in mice, which may be related to inhibition of macrophage polarization into M1 type and alleviation of inflammatory responses.

Objective:To evaluate the relationship between heme oxygenase-1 (HO-1) and peroxisome proliferator-activated receptor γ (PPARγ) during alveolar macrophage polarization in a mouse model of endotoxin-induced acute lung injury (ALI).Methods:Thirty clean-grade male C57BL/6 mice (24 wide-type mice and 6 HO-1 knockout mice), aged 6-8 weeks, weighing 18-22 g, were studied.Wide-type mice were divided into 4 groups ( n=6 each) using a random number table method: control group (C group), ALI group, ALI+ HO-1 agonist hemin group (ALI+ H group), and ALI+ hemin+ PPARγ antagonist T0070907 group (ALI+ H+ T group).HO-1 knockout mice in which the ALI model was developed served as ALI+ HO-1 -/- group.ALI model was developed by injecting lipopolysaccharide (LPS) 15 mg/kg via the tail vein in anesthetized animals.T0070907 1.5 mg/kg was intraperitoneally injected at 1 h before LPS administration in ALI+ H+ T group, and hemin 50 mg/kg was intraperitoneally injected at 30 min before LPS administration in ALI+ H group and ALI+ H+ T group.Mice were sacrificed at 12 h after LPS administration, and lung tissues were obtained to measure the wet to dry weight ratio (W/D ratio), to observe pathological changes which were scored, and to determine the F4/80+ /CD86+ labeled M1 alveolar macrophages and the F4/80+ /CD206+ labeled M2 alveolar macrophages (by flow cytometry), contents of M1 macrophage-related genes inducible nitric oxide synthase (iNOS) and M2 macrophage-related genes Arginase-1 (Arg-1) (by enzyme-linked immunosorbent assay), and the expression of HO-1 and PPARγ (by Western blot). Results:Compared with C group, the lung injury score, W/D ratio, levels of CD86 and CD206, and contents of iNOS and Arg-1 were significantly increased, and PPARγ expression was up-regulated in the other four groups ( P<0.05), and HO-1 protein expression was up-regulated in ALI, ALI+ H and ALI+ H+ T groups ( P<0.05).Compared with ALI group, the lung injury score, W/D ratio, and levels of CD86 and iNOS were significantly increased, the levels of CD206 and Arg-1 were decreased, and the expression of HO-1 and PPARγ was down-regulated in ALI+ HO-1 -/- group, the lung injury score, W/D ratio and levels of CD86 and iNOS were significantly decreased, the levels of CD206 and Arg-1 were increased, and the expression of HO-1 and PPARγ was up-regulated in ALI+ H group ( P<0.05), and no significant change was found in the parameters mentioned above in ALI+ H+ T group ( P>0.05).Compared with ALI+ H group, the lung injury score, W/D ratio and levels of CD86 and iNOS were significantly increased, the levels of CD206 and Arg-1 were decreased, the expression of PPARγ was down-regulated ( P<0.05), and no significant change was found in the expression of HO-1 in ALI+ H+ T group ( P>0.05). Conclusions:HO-1 can up-regulate the expression of PPARγ, inhibit the polarization of alveolar macrophages toward M1 phenotype and promote the polarization toward M2 phenotype, thus playing an endogenous protective role in endotoxin-induced ALI in mice.

Objective:To investigate the effect of electroacupuncture (EA) on synaptic damage to hippocampal neurons in rats with sepsis-associated encephalopathy (SAE).Methods:A total of 48 healthy adult male Sprague-Dawley rats, weighing 250-300 g, were divided into 4 groups ( n=12 each) using a random number table method: sham operation group (Sham group), SAE group, SAE+ EA group and SAE+ sham EA group (SAE+ SEA group). SAE was induced by cecal ligation and puncture in anesthetized rats.Baihui, Quchi and Zusanli acupoints were stimulated with constant voltage (2/15 Hz) and disperse-dense waves for 30 min once a day for 10 consecutive days, and the stimulation intensity was defined as less than 1.5 mA causing slight muscle contraction at 2 days before operation in group SAE+ EA.In group SAE+ SEA, stimulating electrodes were placed at the points 5 mm lateral to the corresponding acupoints, but no electrical stimulation was applied.On day 14 after operation, the rats were sacrificed, and hippocampal tissues were obtained and stained with haematoxylin and eosin for examination of the pathological changes in the hippocampal CA1 region, for determination of the expression of synaptophysin (SYN) and postsynaptic density protein 95 (PSD-95) (by Western blot), and for calculation of dendritic spine density of neurons in the hippocampal CA1 area (using Golgi staining) and pyramidal neurons counts. Results:Compared with Sham group, the expression of SYN and PSD-95 in hippocampus was significantly decreased, and the basal and apical dendrite spine density of neurons in hippocampal CA1 area was decreased in SAE group, the expression of PSD-95 was decreased, and the apical dendrite spine density of neurons in the hippocampal CA1 area was increased in SAE+ EA group, and the pyramidal neuron counts in the hippocampal CA1 area were reduced in SAE, SAE+ EA and SAE+ SEA groups ( P<0.05). Compared with group SAE, the expression of SYN and PSD-95 was significantly up-regulated, the basal and apical dendrite spine density of neurons in the hippocampal CA1 area was increased and the pyramidal neuron counts were increased in group SAE+ EA ( P<0.05), the pathological damage of hippocampal CA1 area was alleviated and no significant change was found in the parameters mentioned above in group SAE+ SEA ( P>0.05). Compared with group SAE+ EA, the expression of SYN and PSD-95 was down-regulated, the basal and apical dendrite spine density of neurons in the hippocampal CA1 area was decreased, and the pyramidal neuron counts were reduced in SAE+ SEA group ( P<0.05). Conclusion:The mechanism by which EA alleviates SAE may be related to reducing synaptic damage to hippocampal neurons in rats.

Objective:To evaluate the effect of electroacupuncture (EA) pretreatment on oxidative stress response of hippocampus in rats with sepsis-associated encephalopathy (SAE) and the relationship with nuclear factor E2-related factor 2 (Nrf2)/heme oxygenase-1 (Nrf2/HO-1) signaling pathway.Methods:A total of 64 healthy adult male Sprague-Dawley rats, weighing 250-300 g, were divided into 4 groups ( n=16 each) using a random number table method: sham operation group (Sham group), SAE group, SAE+ EA group and SAE plus sham EA group (SAE+ SEA group). In SAE+ EA group, Baihui, Quchi and Zusanli acupoints were stimulated for 30 min once a day for 5 consecutive days.Sepsis was induced by cecal ligation and puncture immediately after the end of the last EA.At 1 and 7 days after establishment of the model, the hippocampal malondialdehyde (MDA) and superoxide dismutase (SOD) levels were detected by enzyme-linked immunosorbent assay, the expression of hippocampal Nrf2 mRNA was detected using real-time reverse transcription polymerase chain reaction, and the expression of Nrf2 and HO-1 was determined by Western blot.At 3-7 days after establishment of the model, cognitive function was assessed using the Morris water maze test, and the escape latency and the target quadrant exploration time were recorded. Results:Compared with Sham group, the content of MDA was significantly increased and the activity of SOD was decreased at 1 and 7 days after establishment of the model, the expression of Nrf2 protein and mRNA and HO-1 was down-regulated at day 7 after establishment of the model, the escape latency was prolonged, and the target quadrant exploration time was shortened in SAE group ( P<0.05). Compared with SAE group, the content of MDA was significantly decreased and the activity of SOD was increased at 1 and 7 days after establishment of the model, the expression of Nrf2 protein and mRNA and HO-1 was up-regulated at day 7 after establishment of the model, the escape latency was shortened, and the target quadrant exploration time was prolonged in group SAE+ EA ( P<0.05), and no significant change was found in the parameters mentioned above in group SAE+ SEA ( P>0.05). Conclusion:EA pretreatment can reduce oxidative stress response of hippocampus in rats with SAE, and the mechanism may be related to activating Nrf2/HO-1 signaling pathway.

Objective:To evaluate the role of heme oxygenase-1 (HO-1) in electroacupuncture (EA)-induced alleviation of cognitive dysfunction in mice with sepsis-associated encephalopathy (SAE) and the relationship with mitochondrial fusion-division balance.Methods:Thirty clean-grade male C57BL/6 mice (24 wide-type mice and 6 HO-1 knockout mice), aged 6-8 weeks, weighing 18-22 g, were studied.Twenty-four wide-type mice were divided into 4 groups ( n=6 each) using a random number table method: control group (group C), SAE group, SAE plus EA group (group SAE+ EA), and SAE plus sham EA group (group SAE+ SEA). HO-1 knockout mice in which EA intervention was performed after establishing SAE model served as SAE plus EA plus HO-1 knockout group (group SAE + EA+ H). Sepsis was induced by intraperitoneally injecting lipopolysaccharide 15 mg/kg.EA of Zusanli and Baihui acupoints lasting 30 min was performed after intraperitoneal injection of lipopolysaccharide once a day for 5 consecutive days in SAE+ EA and SAE+ EA+ H groups.Cognitive function was assessed using Morris water maze test before stimulation every day.The mice were sacrificed, and hippocampal tissues were removed for detection of the expression of mitofusin 2 (Mfn2), optic atrophy 1 (OPA1) and mitochondrial dynamin-related protein 1 (Drp1) by Western blot. Results:Compared with group C, the expression of Mfn2 and OPA1 was significantly down-regulated, the escape latency was prolonged, and the time spent in the target quadrant was shorted in SAE, SAE+ SEA and SAE+ EA+ H groups, and the expression of Drp1 was significantly up-regulated in SAE, SAE+ EA, SAE+ SEA and SAE+ EA+ H groups ( P<0.05). Compared with group SAE, the expression of Mfn2 and OPA1 was significantly up-regulated, the expression of Drp1 was down-regulated, the escape latency was shortened, and the time spent in the target quadrant was prolonged in group SAE+ EA ( P<0.05), and no significant change was found in the parameters mentioned above in group SAE+ SEA ( P>0.05). Compared with group SAE+ EA, the expression of Mfn2 and OPA1 was significantly down-regulated, the expression of Drp1 was up-regulated, the escape latency was prolonged, and the time spent in the target quadrant was shortened in SAE+ SEA and SAE+ EA+ H groups ( P<0.05). Conclusion:HO-1 is involved in EA-induced alleviation of cognitive dysfunction in mice with SAE, and the mechanism may be related to the regulation of mitochondrial mitochondrial fusion-division balance.

Objective:To evaluate the effect of electroacupuncture (EA) on lung injury caused by extremity ischemia-reperfusion.Methods:Forty-five American Society of Anesthesilogists physical status ⅠorⅡpatients, aged 20-60 yr, with body mass index of 18-28 kg/m 2, undergoing unilateral lower extremity operation requiring tourniquet with neuraxial anesthesia were divided into 3 groups ( n=15 each) using a random number table method: control group (C group), EA group and EA at non-acupoint group (group N). Bilateral acupoints Feshu and Zusanli were stimulated with disperse-dense waves, frequency 2/15 Hz, the current intensity the maximum current that patients could tolerant until the end of surgery in group EA.EA was performed at the points 1 cm lateral to the acupoints of Feshu and Zusanli in group N. Before anesthesia (T 1) and at 10, 30 and 60 min after tourniquet loosening (T 2-4), blood samples were collected from the radial artery for blood gas analysis, the partial pressure of arterial oxygen(PaO 2) and arterial carbon dioxide partial pressure (PaCO 2) were recorded, alveolar-arterial oxygen partial pressure difference (P A-aDO 2), oxygenation index (OI) and respiratory index (RI) were calculated, the malondialdehyde (MDA) content was measured by thiobarbituric acid method, the concentration of serum nitric oxide (NO) was determined by nitrate reductase method, and the concentrations of serum endothelin-1 (ET-1) and interleukin-6 (IL-6) were measured by enzyme-linked immunosorbent assay. Results:Compared with the baseline at T 1, OI and RI were significantly decreased, P A-aO 2 was increased, and serum MDA, IL-6, ET-1 and NO levels were increased at T 2-4 in three groups ( P<0.05). Compared with group C, OI was significantly increased, P A-aO 2 and RI were decreased, serum MDA, IL-6, ET-1 and NO levels were decreased at T 2-4 in group EA ( P<0.05). Conclusion:EA can reduce lung injury caused by extremity ischemia-reperfusion, and the mechanism may be related to maintaining NO/ET-1 balance.

Objective:To evaluate the role of hippocampal hemeoxygenase-1 (HO-1) in electroacupuncture (EA)-induced reduction of lipopolysaccharide (LPS)-induced brain injury in mice.Methods:Twenty-four healthy adult C57BL/6J mice of both sexes, weighing 18-22 g, were divided into 4 groups ( n=6 each) using a random number table method: control group (group C), LPS-induced brain injury group (LPS group), LPS plus EA group, and LPS plus EA plus HO-1 inhibitor zinc protoporphyria (ZnPP) group (LPS+ EA+ ZnPP group). A virus carrying calcium ion fluorescent probes was injected into and an optical fiber was implanted into the hippocampal CA1 region to record changes in the calcium fluorescence signals.Three weeks later, Baihui, Quchi and Zusanli acupoints were stimulated with constant voltage (2/15 Hz) and disperse-dense waves for 30 min once a day for 5 consecutive days, and the stimulation intensity was defined as less than 1 mA causing slight muscle contraction.ZnPP 50 μmol/kg was intraperitoneally injected at 12 h before each stimulation in LPS+ EA+ ZnPP group, and the equal volume of normal saline was given instead in the other groups.After the end of EA stimulation on the last day, LPS 5 mg/kg was intraperitoneally injected to induce brain injury.Open field tests were performed at 1 day after LPS injection to record the number of rearing and amplitude of neuronal calcium signals during rearing.Novel object recognition tests were conducted at 3 days after LPS injection, and the exploration index and amplitude of neuronal calcium signals while exploring novel objects were recorded.The mice were sacrificed after the end of behavioral testing, and the brain tissues were obtained and stained by Nissl, and the neurons in the hippocampal CA1 region were counted. Results:Compared with group C, the number of rearing and amplitude of calcium signals in neurons in the hippocampal CA1 region during rearing were significantly decreased, the exploration index and amplitude of calcium signals in neurons in the hippocampal CA1 region while exploring novel objects were decreased, and the neuron counts were reduced in LPS, LPS+ EA and LPS+ EA+ ZnPP groups ( P<0.05 or 0.01). Compared with group LPS, the number of rearing and amplitude of calcium signals in neurons in the hippocampal CA1 region during rearing were significantly increased, and the exploration index and amplitude of calcium signals in neurons in the hippocampal CA1 region while exploring novel objects were increased in group LPS+ EA ( P<0.05), and no significant change was found in the parameters mentioned above in group LPS+ EA+ ZnPP ( P>0.05). Compared with group LPS+ EA, the number of rearing and amplitude of calcium signals in neurons in the hippocampal CA1 region during rearing were significantly decreased, and the exploration index and amplitude of calcium signals in neurons in the hippocampal CA1 region while exploring novel objects were decreased in group LPS+ EA+ ZnPP ( P<0.05). Conclusion:The mechanism by which EA reduces LPS-induced brain injury is related to the activation of the endogenous protective mechanism HO-1 in mice.

Objective:To evaluate the relationship between melatonin receptors and mitochondrial fission proteins and to clarify the mechanism of melatonin alleviating lipopolysaccharide(LPS)-induced damage to type Ⅱ alveolar epithelial cells of rats.Methods:The rat type Ⅱalveolar epithelial cells were seeded in 6-well plates at a density of 2×10 5 cells/ml and divided into 5 groups ( n=10 each) using a random number table method: control group (C group), LPS group (L group), LPS plus melatonin group (LM group), LPS plus melatonin receptor blocking group (LL group), and LPS plus melatonin plus melatonin receptor blocker group (LML group). The model of LPS-induced damage to cells was established by incubating with LPS 10 μg/ml for 24 h. Melatonin 0.1 mmol/L and/or melatonin receptor blocker luzindole 0.2 μmol/L was added in LM group, LL group and LML group.The concentrations of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) were measured by enzyme-linked immunosorbent assay after the end of incubation.The mitochondrial respiratory control rate (RCR) was measured by GENMED purified mitochondrial RCR quantitative detection kit in each group.Western blot was used to detect the expression of dynamin-related protein 1 (Drp1) and mitochondrial adaptor fission 1 (Fis1). Results:Compared with C group, the concentrations of TNF-α and IL-6 in culture medium were significantly increased, RCR was decreased, and the expression of Drp1 and Fis1 was up-regulated in L, LM, LL and LML groups ( P<0.05). Compared with L group, the concentrations of TNF-α and IL-6 in culture medium were significantly decreased, RCR was increased, and the expression of Drp1 and Fis1 was down-regulated in LM group ( P<0.05), and no significant change was found in parameters mentioned above in LL group ( P>0.05). Compared with LM group, the concentrations of TNF-α and IL-6 in culture medium were significantly increased, RCR was decreased, and the expression of Drp1 and Fis1 was up-regulated in LML group ( P<0.05). Conclusion:The mechanism by which melatonin attenuates LPS-induced damage to type Ⅱ alveolar epithelial cells is related to activating melatonin receptors and inhibiting the expression of mitochondrial fission proteins in rats.