GLP-2 ameliorates D-galactose induced muscle aging by IGF-1/Pi3k/Akt/FoxO3a signaling pathway in C2C12 cells and mice.

BACKGROUND: The study aimed to investigate the effect of Glucagon-like peptide-2 (GLP-2) on muscle aging in vivo and in vitro. METHODS: Six-week-old C57BL/6J mice were administered with D-galactose (200 mg/kg/day, intraperitoneally) for 8weeks, followed by daily subcutaneous injections of GLP-2 (300 or 600 µg/kg/day) for 4weeks. Skeletal muscle function and mass were evaluated using relative grip strength and muscle weight. The sizes and types of muscle fibers and apoptosis were assessed through histological analysis, immunofluorescence staining, and TUNEL staining, respectively. C2C12 myotubes were treated with D-galactose (40 mg/mL) and GLP-2. Protein expression of differentiation-related myogenic differentiation factor D (MyoD), myogenin (MyoG), and myosin heavy chain (Myhc), degradation-related Muscle RING finger 1 (MuRF-1), and muscle atrophy F-box (MAFbx)/Atrogin-1, and apoptosis-related B-cell leukemia/lymphoma 2 (Bcl-2) and Bax, were assessed using western blots. The Pi3k inhibitor LY294002 was applied to investigate whether GLP-2 regulated myogenesis and myotube aging via IGF-1/Pi3k/Akt/FoxO3a signaling pathway. RESULTS: The results demonstrated that GLP-2 significantly reversed the decline in muscles weight, relative grip strength, diameter, and cross-sectional area of muscle fibers induced by D-galactose in mice. Apart from suppressing the expressions of MuRF-1 and Atrogin-1 in the muscles and C2C12 myotubes, GLP-2 significantly increased the expressions of MyoD, MyoG, and Myhc compared to the D-galactose. GLP-2 significantly suppressed cell apoptosis. Western blot analysis indicated that the regulation of GLP-2 may be attributed to the activation of theIGF-1/Pi3k/Akt/FoxO3a phosphorylation pathway. CONCLUSIONS: This study suggested that GLP-2 ameliorated D-galactose induced muscle aging by IGF-1/Pi3k/Akt/FoxO3a pathway.

SGLT2 inhibitor empagliflozin alleviates cardiac remodeling and contractile anomalies in a FUNDC1-dependent manner in experimental Parkinson's disease.

Recent evidence shows a close link between Parkinson's disease (PD) and cardiac dysfunction with limited treatment options. Mitophagy plays a crucial role in the control of mitochondrial quantity, metabolic reprogramming and cell differentiation. Mutation of the mitophagy protein Parkin is directly associated with the onset of PD. Parkin-independent receptor-mediated mitophagy is also documented such as BCL2/adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP3) and FUN14 domain containing 1 (FUNDC1) for receptor-mediated mitophagy. In this study we investigated cardiac function and mitophagy including FUNDC1 in PD patients and mouse models, and evaluated the therapeutic potential of a SGLT2 inhibitor empagliflozin. MPTP-induced PD model was established. PD patients and MPTP mice not only displayed pronounced motor defects, but also low plasma FUNDC1 levels, as well as cardiac ultrastructural and geometric anomalies (cardiac atrophy, interstitial fibrosis), functional anomalies (reduced E/A ratio, fractional shortening, ejection fraction, cardiomyocyte contraction) and mitochondrial injury (ultrastructural damage, UCP2, PGC1α, elevated mitochondrial Ca2+ uptake proteins MCU and VDAC1, and mitochondrial apoptotic protein calpain), dampened autophagy, FUNDC1 mitophagy and apoptosis. By Gene set enrichment analysis (GSEA), we found overtly altered glucose transmembrane transport in the midbrains of MPTP-treated mice. Intriguingly, administration of SGLT2 inhibitor empagliflozin (10 mg/kg, i.p., twice per week for 2 weeks) in MPTP-treated mice significantly ameliorated myocardial anomalies (with exception of VDAC1), but did not reconcile the motor defects or plasma FUNDC1. FUNDC1 global knockout (FUNDC1-/- mice) did not elicit any phenotype on cardiac geometry or function in the absence or presence of MPTP insult, but it nullified empagliflozin-caused cardioprotection against MPTP-induced cardiac anomalies including remodeling (atrophy and fibrosis), contractile dysfunction, Ca2+ homeostasis, mitochondrial (including MCU, mitochondrial Ca2+ overload, calpain, PARP1) and apoptotic anomalies. In neonatal and adult cardiomyocytes, treatment with PD neurotoxin preformed fibrils of α-synuclein (PFF) caused cytochrome c release and cardiomyocyte mechanical defects. These effects were mitigated by empagliflozin (10 µM) or MCU inhibitor Ru360 (10 µM). MCU activator kaempferol (10 µM) or calpain activator dibucaine (500 µM) nullified the empagliflozin-induced beneficial effects. These results suggest that empagliflozin protects against PD-induced cardiac anomalies, likely through FUNDC1-mediated regulation of mitochondrial integrity.

Metformin attenuates inflammation and boosts autophagy in the liver and intestine of chronologically aged rats.

BACKGROUND: Our previous studies found that autophagy levels in liver and intestinal segments of naturally aging rats were downregulated, and the expression of pro-inflammatory factors was increased. The increased expression of pro-inflammatory factors might be related to the downregulation of autophagy. AMPK is the most critical upstream targeting and regulating molecule of autophagy, and Metformin, as an agonist of AMPK, has the effects of anti-inflammation and anti-aging. We pretreated 29-month-old naturally aging rats with Metformin for a short period and observed the changes in autophagy levels and pro-inflammatory factors in the liver, ileum, and colon after 31 days of intervention and preliminarily investigated the mechanism of its action. METHODS: 29-month-old SPF male Wistar rats were divided into three groups: The control group, the Metformin 100 mg/kg intervention group, and the Metformin 250 mg/kg intervention group, with eight rats in each group. At 29 months, different concentrations of Metformin (100 mg/kg, 250 mg/kg) were given by gavage once a day until 30 months, and the control group was kept generally until 30 months. Western Blot was used to assess the expression levels of AMPK, P-AMPK, LC3, and P62 proteins in the liver and intestinal tissues. Intestinal and liver tissues were immunofluorescence labeled for LC3 and P62 proteins. Moreover, RT-qPCR was conducted to detect the expression levels of pro-inflammatory factors IL-1ß, TNF-α, IL-6, and MMP-9 mRNA in liver and intestinal tissues. RESULTS: Short-term Metformin pretreatment (31 days) in naturally aging rats (29 months old) increased autophagy levels and down-regulated the expression of various pro-inflammatory cytokines (IL-1ß, TNF-α, MMP-9, and IL-6) in various intestinal segments and the liver-the expression of LC3II protein enriched with the increase of Metformin concentration. The level of P62 protein decreased with the accumulation of Metformin concentration. And a higher concentration of Metformin was associated with increased expression of P-AMPK protein. CONCLUSIONS: Metformin intervention can boost the autophagy level in the liver and intestine and reduce the expression of aging-related inflammatory factors in aged rats, and these effects may be related to the increase of the AMPK phosphorylation level.

The Relationship between Skeletal Muscle Mass and Bone Mass at Different Sites in Older Adults.

INTRODUCTION: It has been well recognized that sarcopenia is closely related with osteoporosis, while the relationship between bone mass at different sites and muscle mass remains largely unexplored. This study aims to explore the relationship between bone mass at different sites and skeletal muscle mass in older adults. METHODS: A total of 228 patients over 65 years old were enrolled in this study, and then 180 valid participants with accessible dual-energy X-ray absorptiometry (DXA) scanning data and absence of malignant tumors, mobility disorders, serious liver and kidney disease, and cardiac insufficiency were selected (138 male and 42 female). These individuals were further divided into control group and low skeletal muscle mass index (SMI) group. DXA scanning was used to access skeletal muscle mass and bone mass. SMI or body mass index was defined as appendicular muscle mass or weight divided by squared height, respectively. Low SMI <7.0 kg/m2 in male or <5.4 kg/m2 in female was defined as low SMI; while the bone density score at or below 2.5 standard deviations (T-score) below normal peak bone values, was regarded as osteoporosis. RESULTS: The average age of enrolled patients was 82.72 years; the ratios of osteoporosis, low SMI, and low SMI with osteoporosis were 48.8%, 23.3%, and 15.0%, respectively. Compared with the control group, the prevalence of osteoporosis was higher, and the total bone mass and bone mass at various sites including limbs, spine, and pelvis, were all lower in low SMI group. Correlation analysis showed that SMI was positively related with total bone mass and bone mass at various sites. Covariance analysis showed that only total bone mass and appendicular bone mass decreased with decreasing SMI. After multiple adjustment, osteoporosis was positively related with the prevalence of low SMI, as evidenced by logistic regression analysis (odds ratio = 1.33, 95% confidential interval: 1.04-3.24, p = 0.045). Furthermore, compared with the highest quartile of appendicular bone mass, the lowest quartile was related with the increasing prevalence of low SMI (odds ratio = 7.29, 95% confidential interval: 1.21-67.45, p = 0.042). CONCLUSION: Compared with the other sites, the bone mass reduction at limbs of older adults was positively associated with skeletal muscle loss. It may be more beneficial to increase bone mass at the limbs for improved sarcopenia prevention and therapy. Further investigations are needed to explore the effects of other confounders (e.g., energy, calcium and vitamin D intake, and physical activity) on the osteoporosis and sarcopenia in older adults.

Age-Related Changes in the Composition of Intestinal Microbiota in Elderly Chinese Individuals.

INTRODUCTION: Intestinal microbiota affects human health and aging. The composition of intestinal microbiota and inflammation indices in elderly Chinese, especially centenarians, is unclear. OBJECTIVE: This study aimed to explore the relationships between intestinal microbiota and inflammation in healthy housebound elders in Shanghai, China. METHODS: We enrolled 156 differently aged adults and assigned them into 4 groups: those aged 35-64 years were assigned into Group AD; 65-79 years into Group YO; 80-94 years into Group MO; and 95-102 years into Group VO. RESULTS: The diversity of intestinal microbiota in Group VO was significantly reduced compared with that of the other 3 groups. Bacteroidetes abundance in Group VO was significantly lower than that in Groups AD, YO, or MO; Proteobacteria abundance showed the opposite trend. Akkermansia, Bifidobacterium, and Lactobacillus abundance in Group VO was significantly higher than that in the other 3 groups; Anaerostipes, Butyricicoccus, and Faecalibacterium abundance showed the opposite trend. Solobacterium abundance in Group VO was significantly lower than that in the other 3 groups; Campylobacter, Porphyromonas, Escherichia, and Pseudomonas abundance showed the opposite trend. Plasma levels of tumor necrosis factor-α (TNF-α), IL-6, and IL-8 in Group VO were significantly higher than those in Groups AD, YO, and MO, while those in Group MO were significantly higher than those in Groups AD and YO. IL-1ß and IL-10 plasma levels were not significantly different among the 4 groups. Proteobacteria abundance was positively correlated with TNF-α and IL-8 levels, while Campylobacter abundance was positively correlated with those of TNF-α and IL-6. Anaerostipes and Faecalibacterium abundance was negatively correlated with TNF-α and IL-6 levels. CONCLUSIONS: The diversity of intestinal microbiota in the oldest participants (centenarians) decreased significantly, with several beneficial bacterial strains showing increased or decreased abundance; harmful bacterial species showed a similar trend. Our oldest participants (centenarians) demonstrated significantly increased levels of pro-inflammatory cytokines, which may be related to inflammaging.

Glucagon like peptide 2 has a positive impact on osteoporosis in ovariectomized rats.

AIMS: In this study, we evaluate the effects of glucagon-like peptide 2 (GLP-2) on bone microarchitecture, bone turnover markers (BTMs) and inflammation markers in ovariectomized (OVX) rats. MATERIAL AND METHODS: In total, 31 Sprague-Dawley rats were divided into the following three groups: sham (control sham-operated with vehicle, n = 7), OV (OVX with vehicle, n = 12), and GLP-2 (OVX with GLP-2, n = 12). Intervention began at the 12th week after surgery and lasted for 4 weeks. The dosage of the GLP-2 was 160 µg/kg/d through subcutaneous injections, and normal saline was used as the vehicle agent. After 4 weeks of treatment, serum BTM and inflammation marker levels were measured by ELISA, and femora samples were analyzed by qRT-PCR, micro-CT, histology and histomorphometry. KEY FINDINGS: After 4 weeks of treatment, serum TRAcP-5b and RANKL levels as well as the CTX-1/P1NP ratio in the GLP-2 group decreased, and ALP activity, P1NP level, and OPG/RANKL ratio increased significantly; qRT-PCR analysis showed that mRNA levels of RANKL decreased, and Runx2, ALP, and Col-1 levels as well as the OPG/RANKL ratio increased significantly in the GLP-2 group compared with the OV group. In bone histology analysis, GLP-2 significantly decreased the AV/MV, Oc.N and Oc.S but increased the Ob.N, BFR and MAR. Analysis with µ-CT showed that the BMD, BV/TV, Tb.N and Conn.D increased significantly in the GLP-2 group compared with the OV group. The levels of serum inflammation markers TNF-α, IL-1ß and IL-6 decreased, and TGF-ß levels increased in the GLP-2 group compared with the OV group. SIGNIFICANCE: GLP-2 may have a positive impact on osteoporosis by promoting bone formation, inhibiting bone resorption and decreasing circulatory inflammation in ovariectomized rats.

Regulation of the NLRP3 inflammasome and macrophage pyroptosis by the p38 MAPK signaling pathway in a mouse model of acute lung injury.

Acute lung injury and acute respiratory distress syndrome (ALI/ARDS) is characterized by uncontrolled progressive lung inflammation. Macrophages serve a key role in the pathogenesis of ALI/ARDS. Macrophage pyroptosis is a process of cell death releasing the proinflammatory cytokines interleukin (IL)­1ß and IL­18. It was hypothesized that macrophage pyroptosis may partially account for the uncontrolled lung inflammation of ALI/ARDS. In the present study, greater macrophage pyroptosis in lipopolysaccharide (LPS)­treated macrophages and the ALI/ARDS mouse model was observed. The expression of nucleotide­binding domain, leucine­rich­containing family, pyrin domain­containing (NLRP)3 and IL­1ß and cleavage of caspase­1 were significantly elevated following LPS treatment accompanied by greater activation of p38 mitogen­activated protein kinase (MAPK) signaling in vitro and in vivo. However, blocking p38 MAPK signaling through the inhibitor SB203580 significantly suppressed the acute lung injury and excessive lung inflammation in vivo, consistent with the reduced expression of the NLRP3 inflammasome and IL­1ß and cleavage of caspase­1. Pretreatment of the rat NR8383 macrophage cell line with SB203580 significantly decreased the population of caspase­1+PI+ pyroptotic cells and expression of NLRP3/IL­1ß. However, a larger population of Annexin V+PI­ apoptotic cells was observed following blocking of the p38 MAPK signaling pathway. The results indicated that blockage of p38 MAPK signaling pathway skewed macrophage cell death from proinflammatory pyroptosis towards non­inflammatory apoptosis. These effects may contribute to attenuated acute lung injury and excessive inflammation in the SB203580­treated mice. The results may provide a novel therapeutic strategy for the treatment of uncontrolled lung inflammation in patients with ALI/ARDS.

MD-2 regulates LPS-induced NLRP3 inflammasome activation and IL-1beta secretion by a MyD88/NF-κB-dependent pathway in alveolar macrophages cell line.

Myeloid differentiation protein 2 (MD-2) is required in the recognition of lipopolysaccharide (LPS) by toll-like receptor 4 (TLR4), and participates in LPS-induced alveolar macrophage (AM) inflammation during acute lung injury (ALI). Activation of the NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome aggravates inflammation in LPS-induced ALI. However, there is currently little known about the relationship between MD-2 signaling and the NLRP3 inflammasome. This study showed that NLRP3 expression, IL-1beta (IL-1ß) secretion, and pyroptosis were up-regulated after LPS stimulation in the NR8383 AM cell-line. MD-2 gene knock-down reduced LPS-induced mRNA and protein expression of NLRP3 and IL-1ß secretion in NR8383 cells, and inhibited the MyD88/NF-κB signaling pathway. Conversely, over-expression of MD-2 not only heightened NLRP3, MyD88, and NF-κB p65 protein expression, it also aggravated the LPS-induced inflammatory response. Furthermore, the NF-κB inhibitor SN50 had a beneficial role in decreasing NLRP3 and caspase-1 mRNA and protein expression. The observations suggest that MD-2 helps to regulate LPS-induced NLRP3 inflammasome activation and the inflammatory response in NR8383 cells, and likely does so by affecting MyD88/NF-κB signaling.

Role of transgelin-2 in diabetes-associated pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy with poor prognosis. Diabetes is a significant risk factor for PDAC and >50% of PDAC patients have concomitant diabetes. How diabetes influences the initiation and progression of PDAC remains elusive. Here, we show that transgelin-2 is dominantly expressed in PDAC tissues compared with adjacent normal tissues. The high level of transgelin-2 indicates poor survival of patients with PDAC. Remarkably, transgelin-2 expression is correlated with diabetic status. Hyperinsulinemia is frequently observed in type 2 diabetes. Our results indicate that upregulation of transgelin-2 is induced by insulin via sterol regulatory element-binding protein (SREBP)-1-mediated transcription in PDAC cells. Transgelin-2 is a novel target of SREBP-1. Our data support a novel mechanism in diabetes-associated PDAC by which transgelin-2 mediates proliferation of PDAC cells upon insulin stimulation. The insulin/SREBP-1/transgelin-2 network should be further explored as a diagnostic marker or a novel therapeutic target for diabetes-associated PDAC.

Phosphorylation of Ser6 in hnRNPA1 by S6K2 regulates glucose metabolism and cell growth in colorectal cancer.

Abnormal glucose metabolism is critical in colorectal cancer (CRC) development. Expression of the pyruvate kinase (PK) M2 isoform, rather than the PKM1 isoform, serves important functions in reprogramming the glucose metabolism of cancer cells. Preferential expression of PKM2 is primarily driven by alternative splicing, which is coordinated by a group of splicing factors including heterogeneous nuclear ribonucleoprotein (hnRNP)A1, hnRNPA2 and RNA binding motif containing. However, the underlying molecular mechanisms associated with cancer cell expression of PKM2, instead of PKM1, remain unknown. The mRNA levels of PKM isoform and glucose metabolism were analyzed in CRC cells. The results of the present study indicated that S6 kinase 2 (S6K2) promotes glycolysis and growth of CRC cells by regulating alternative splicing of the PKM gene. In addition, chromatin immunoprecipitation assay indicated that S6K2 phosphorylation of Ser6 of hnRNPA1 facilitated hnRNPA1 binding to the splicing site of the PKM gene. As a result, cancer cells preferentially expressed the PKM2 isoform, instead of the PKM1 isoform. Furthermore, Cox regression analysis demonstrated that the phosphorylation of Ser6 of hnRNPA1 was a predictor of poor prognosis for patients with CRC. Therefore, the results of the present study revealed that the phosphorylation of Ser6 in hnRNPA1 by S6K2 was a novel mechanism underlying glucose metabolic reprogramming, and suggested that S6K2 is a potential therapeutic target for CRC treatment.

SREBP1 regulates tumorigenesis and prognosis of pancreatic cancer through targeting lipid metabolism.

Sterol regulatory element-binding protein 1 (SREBP1) is a known transcription factor of lipogenic genes, which plays important roles in regulating de novo lipogenesis. Accumulating evidences indicate SREBP1 is involved in tumorigenesis, yet its role in pancreatic cancer remains unclear. Here, we explored the expression characteristic and function of SREBP1 in pancreatic cancer. Analysis of 60 patients with pancreatic ducat cancer showed that SREBP1 level was significantly higher in pancreatic cancer than that in adjacent normal tissues. High expression of SREBP1 predicted poor prognosis in patients with pancreatic cancer. Multivariate analysis revealed that SREBP1 was an independent factor affecting overall survival. SREBP1 silencing resulted in proliferation inhibition and induction of apoptosis in pancreatic cancer cells. Mechanistically, lipogenic genes (acetyl-CoA carboxylase (ACC), fatty acid synthase (FASN), and stearoyl-CoA desaturase-1 (SCD1)) and de novo lipogenesis were promoted by SREBP1. Inhibition of lipogenic genes through specific inhibitors ablated SREBP1-mediated growth regulation. Furthermore, depletion of SREBP1 could suppress lipid metabolism and tumor growth in vivo. Our results indicate that SREBP1 had important role in tumor progression and appears to be a novel prognostic marker for pancreatic cancer.

Plasminogen activator inhibitor-1 regulates LPS induced inflammation in rat macrophages through autophagy activation.

BACKGROUND: The mechanisms by which plasminogen activator inhibitor-1 (PAI-1) regulates inflammation, especially in acute respiratory distress syndrome (ARDS), are largely unknown. OBJECTIVE: To assess the relationship between PAI-1 and autophagy in inflammatory reactions induced by LPS in rat NR8383 cells. METHODS: ELISA was used to assess the amounts of TNF-α, IL-1ß, and PAI-1 in cell culture supernatants; TLR4, MyD88, PAI-1, LC3, Beclin1, and mTOR protein and mRNA levels were determined by western blot and quantitative RT-PCR, respectively; western blot was used to determine NF-κB protein levels. To further evaluate the role of PAI-1, the PAI-1 gene was downregulated and overexpressed using the siRNA transfection technology and the pCDH-PAI-1, respectively. Finally, the GFP Positive Expression Rate Method was used to determine the rate of GFP-LC3 positive NR8383 cells. RESULTS: In LPS-induced NR8383 cells, TNF-α, IL-1ß, and PAI-1 expression levels increased remarkably. Upon PAI-1 knockdown, TNF-α, IL-1ß, PAI-1, TLR4, MyD88, NF-κB, LC3, and Beclin1 levels were decreased, while mTOR increased. Conversely, overexpression of PAI-1 resulted in increased amounts of TNF-α, IL-1ß, PAI-1, TLR4, MyD88, NF-κB, LC3, and Beclin1. However, no significant change was observed in mTOR expression. CONCLUSIONS: In NR8383 cells, PAI-1 contributes in the regulation of LPS-induced inflammation, likely by promoting autophagy.

The pro-apoptotic role of the regulatory feedback loop between miR-124 and PKM1/HNF4α in colorectal cancer cells.

Accumulating evidence indicates that miRNA regulatory circuits play important roles in tumorigenesis. We previously reported that miR-124 is correlated with prognosis of colorectal cancer due to PKM-dependent regulation of glycolysis. However, the mechanism by which miR-124 regulates apoptosis in colorectal cancer remains largely elusive. Here, we show that miR-124 induced significant apoptosis in a panel of colorectal cancer cell lines. The mitochondrial apoptosis pathway was activated by miR-124. Furthermore, the pro-apoptotic role of miR-124 was dependent on the status of PKM1/2 level. PKM1 was required for miR-124-induced apoptosis. Via direct protein-protein interaction, PKM1 promoted HNF4α binding to the promoter region of miR-124 and transcribing miR-124. Moreover, HNF4α or PKM1 had a more dramatic effect on colorectal cancer cell apoptosis in the presence of miR-124. However, inhibition of miR-124 blocked cell apoptosis induced by HNF4α or PKM1. These data indicate that miR-124 not only alters the expression of genes involved in glucose metabolism but also stimulates cancer cell apoptosis. In addition, the positive feedback loop between miR-124 and PKM1/HNF4α plays an important role in colorectal cancer cell apoptosis; it suggests that disrupting this regulatory circuit might be a potential therapeutic tool for colorectal cancer treatment.

Myeloid differentiation protein 2 silencing decreases LPS-induced cytokine production and TLR4/MyD88 pathway activity in alveolar macrophages.

Lipopolysaccharides (LPSs) activate the innate immune response during Gram-negative bacterial infections through the Toll-like receptor 4 (TLR4)/myeloid differentiation protein 2 (MD-2) complex. MD-2 binds LPS with high affinity and is critical for TLR4-dependent signal transduction. However, the exact role of MD-2 on LPS signal transduction and cytokine production in alveolar macrophages (AMs) remains unclear. This study showed that the transcription levels of MD-2, TLR4 and MyD88 in the NR8383 cell line were up-regulated after LPS stimulation and that the increased transcript levels were attenuated after RNA interference of MD-2. Similarly, LPS induced increases in TNF-α, IL-1ß and IL-6 protein levels in NR8383 cell supernatants was significantly inhibited by MD-2 silencing. These results suggest that in association with the TLR4/MyD88 signaling pathway LPS-induced cytokine production can be partially reduced by MD-2 silencing in the rat pulmonary alveolar macrophage cell line NR8383. MD-2 silencing was proved to be a useful tool for testing the role of MD-2 in the LPS signaling pathway and may be a potential therapeutic tool against LPS-induced lung inflammation.

[The effect of lipopolysaccharide on gene expression of TLR4 and MD-2 in rat alveolar macrophage and its secretion of inflammation cytokines].

OBJECTIVE: To investigate the effect of lipopolysaccharide (LPS) on gene expression of Toll-Like receptor 4 (TLR4) and myeloid differentiation protein-2 (MD-2) in rat alveolar macrophage NR8383 cell and its secretion of inflammation cytokines with or without small interference RNA target MD-2 (MD2-siRNA) treatment. METHODS: NR8383 cell was cultured with F-12K medium and stimulated with LPS (0.01 approximately 10 mg/L) for 2 h or stimulated with 1 microg/ml LPS for 2-24 h. MD2-siRNA oligo was transfected into NR8383 cell by Lipofectamine 2000. The expression of TLR4 mRNA and MD-2 mRNA in cell were detected by semi-quantitative revels transcription polymerase (RT-PCR). The contents of TNF-alpha, IL-6 and IL-1beta in the cell cultured supernatant were tested by ELISA. One way ANOVA was used for difference comparison during groups and Pearson correlation was used for correlation analysis. RESULTS: (1) The mRNA expression of TLR4 and MD-2 in control NR8383 cell were 0.52+/-0.05 and 0.44+/-0.09, respectively. There was no obviously change after 0.01 mg/L LPS stimulation. The increase occurred in a dose dependent manner from 0.1 mg/L to 10 mg/L. The highest TLR4 and MD-2 mRNA expression were 0.72+/-0.06 and 0.65+/-0.10 (F=17.255 and 6.045, P<0.01). The changes of TNF-alpha, IL-6 and IL-1beta contents in cell cultured supernatant were similar with that of TLR4 and MD-2 gene expression. TNF-alpha, IL-6 and IL-1beta content were (25.8+/-3.4) ng/L, (62.4+/-4.7) ng/L and (31.6+/-1.7) ng/L in control group, while the corresponding contents were (58.9+/-5.3) ng/L, (96.5+/-3.9) ng/L and (55.4+/-5.4) ng/L after 10 mg/L LPS simulation (F=29.55, 54. 47 and 31.45, P<0. 01). (2) When stimulated with 1 microg/ml LPS, the mRNA expressions of TLR4 and MD-2 in NR8383 cell were increased from hour 2. The highest mRNA expressions of TLR4 and MD-2 occurred at hour 6, and then decreased slowly from hour 8. The mRNA expressions at hour 24 were still higher than those in cells without LPS stimulation (F=5.279 and 4.106, P<0.01). The changes of TNF-alpha, IL-6 and IL-1beta content in cell cultured supernatant were also similar with that of gene expression (F=10.64, 11.23 and 17.58, P<0. 01). The secretion peaks of TNF-alpha and IL-1beta occurred from hour 6 to hour 8, and the secretion peak of IL-6 occurred from hour 8 to hour12. (3) The mRNA expression of MD-2 was related with that of TLR4 positively (r=0.513, P<0.01). (4) The interfere efficiency of MD-2 siRNA was 67%. There was no obvious increase of TNF-alpha, Il-1beta and IL-6 in MD-2 siRNA treated group after LPS stimulation. CONCLUSION: Higher dose LPS can up-regulate the gene expression of TLR4 and MD-2 in rat alveolar macrophage NR8383 cell with a long time and promote the secretion of TNF-alpha, IL-6 and IL-1beta. MD-2 siRNA can inhibit NR8383 cell secrete TNF-alpha, IL-6 and IL-1beta induced by LPS.