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Background The severity of hypoalbuminemia has been sho wn to be related to morbidity and mortality in some critical illnesses, illustra ting the need for better understanding of molecular mechanism of hypoalbuminemia . Lipopolysaccharide (LPS) is a key mediator inducing hypoalbuminemia in sepsis and septic shock. The present study was designed to identify if the reduction of albumin expression is directly induced by LPS and modulated by activated extr acellular signal-regulated protein kinase (ERK) and p38 mitogen-activated prot ein kinase (MAPK) in rat hepatocytes. Methods Primary rat hepatocytes were divided into five groups. In two of them, hepatocytes were treated with normal saline or 1 μg/ml LPS, th en albumin mRNA expression was observed at 0, 2, 8, 12 and 24 hours after treatm ent. In another group, hepatocytes were pretreated with 100, 40 or 20 μmol/L o f cycloheximide (CHX, an inhibitor of protein synthesis) for 30 minutes followed by 1 μg/ml LPS for 24 hours. Then the RNA was extracted from the cells for RT -PCR to detect the expression of albumin. The other two groups were administer ed 1 μmol/L, 10 μmol/L and 50 μmol/L of SB203580 (p38 MAPK inhibitor) or PD98 059 (ERK inhibitor) 30 minutes prior to 1 μg/ml LPS treatment. After 24 hours of LPS treatment, the supernatant was collected and assayed for albumin concentr ations. Data were analyzed by one-way analysis of variance, followed by the Ne wman-Keul test; a P<0.05 was considered significant. Results There was no marked change in albumin mRNA expression i n the control group during 24-hours treatment with normal saline. The reductio n did not occur until 24 hours after LPS treatment, and albumin mRNA decreased b y 30% approximately compared to the control group at 24 hours (0.587 vs 0.832, P=0.007). CHX could inhibit the decline of albumin mRNA induced by LPS an d the effect was correlated with the dose of CHX. The ERK inhibitor PD98059 cau sed a significant increase in LPS-induced albumin production at the three conce ntrations (119.7, 111.4 and 80.0 ng/ml vs 44.4 ng/ml, P=0.0013, 0.0025 and 0.009, respectively), whereas SB203580 obviously blocked albumin reduction in LPS-treated cells at the concentrations of 10 and 50 μmol/L (87.5 a nd 93.6 ng/ml vs 44.4 ng/ml, P=0.0076 and 0.0049, respectively). Conclusions LPS can induce the reduction of albumin expression by new synthesized proteins indirectly, and the process may be related to the si gnal proteins of ERK and p38 kinase. The ERK and p38 kinase are critical signal ing pathways in LPS-induced hypoalbuminemia which is worthwhile to understand i n studying the molecular mechanism of hypoalbuminemia in sepsis and septic shock .
Background The severity of hypoalbuminemia has been sho wn to be related to morbidity and mortality in some critical illnesses, illustra ting the need for better understanding of molecular mechanism of hypoalbuminemia. Lipopolysaccharide (LPS) is a key mediator inducing hypoalbuminemia in sepsis and septic shock. The present study was designed to identify if the reduction of albumin expression is directly induced by LPS and modulated by activated extrinsic signal-regulated protein kinase (ERK) and p38 mitogen-activated prot ein kinase (MAPK) in rat hepatocytes. Methods Primary rat In two of them, the hepatocytes were treated with normal saline or 1 μg / ml LPS, th en albumin mRNA expression was observed at 0, 2, 8, 12 and 24 hours after treatm ent. In another group , hepatocytes were pretreated with 100, 40 or 20 μmol / L of cycloheximide (CHX, an inhibitor of protein synthesis) for 30 minutes followed by 1 μg / ml LPS for 24 hours. Then the RN A was extracted from the cells for RT-PCR to detect the expression of albumin. The other two groups were administer ed 1 μmol / L, 10 μmol / L and 50 μmol / L of SB203580 (p38 MAPK inhibitor) or PD98 059 inhibitor for 30 minutes prior to 1 μg / ml LPS treatment. After 24 hours of LPS treatment, the supernatant was collected and assayed for albumin concentrtions. Data were analyzed by one-way analysis of variance, followed by the Newman-Keul test ; a P <0.05 was considered significant. Results There was no marked change in albumin mRNA expression in the control group during 24-hours treatment with normal saline. The reductio n did not occur until 24 hours after LPS treatment, and albumin mRNA decreased by 30% approximately compared to the control group at 24 hours (0.587 vs 0.832, P = 0.007). CHX could inhibit the decline of albumin mRNA induced by LPS an d the effect was correlated with the dose of CHX. The ERK inhibitor PD98059 cau sed a significant increase in LPS-induced albumin pro ductionat the three concents (119.7, 111.4 and 80.0 ng / ml vs 44.4 ng / ml, P = 0.0013, 0.0025 and 0.009, respectively), while SB203580 obviously blocked albumin reduction in LPS-treated cells at the concentrations of 10 and 50 μmol / L (87.5 a nd 93.6 ng / ml vs. 44.4 ng / ml, P = 0.0076 and 0.0049, respectively). Conclusions LPS can induce the reduction of albumin expression by new synthesized proteins indirectly, and the process may be related to the si gnal proteins of ERK and p38 kinase. The ERK and p38 kinase are critical signaling pathways in LPS-induced hypoalbuminemia which is worthwhile to understand in the molecular mechanism of hypoalbuminemia in sepsis and septic shock.