Lichtman S N, Wang J, Schwab J H, Lemasters J J
Department of Pediatrics, University of North Carolina, Chapel Hill 27599-7220.
Hepatology. 1994 Apr;19(4):1013-22.
Endotoxin (lipopolysaccharide) is a cell wall polymer from gram-negative bacteria that stimulates Kupffer cell release of cytokines such as tumor necrosis factor-alpha and interleukin-1. Another bacterial cell wall polymer in both gram-negative and gram-positive organisms is peptidoglycan-polysaccharide. Lipopolysaccharide and peptidoglycan-polysaccharide exist together in the intestinal lumen and can cross the intestinal mucosa, enter the portal vein and activate Kupffer cells. The purpose of this study was to compare the effects of lipopolysaccharide stimulation and peptidoglycan-polysaccharide stimulation of Kupffer cells on release of tumor necrosis factor-alpha and interleukin-1. Both bacterial polymers caused maximum tumor necrosis factor-alpha release from Kupffer cells after incubation for 4 to 8 hr. Maximum tumor necrosis factor-alpha release induced by 400 ng/ml lipopolysaccharide was 704 +/- 258 pg/ml, compared with 329 +/- 91 pg/ml tumor necrosis factor-alpha after 100 micrograms/ml peptidoglycan-polysaccharide (p < 0.001). Polymyxin B blocked lipopolysaccharide stimulation of tumor necrosis factor-alpha by 95% +/- 5% but blocked peptidoglycan-polysaccharide-stimulated tumor necrosis factor-alpha by 30% +/- 14% (p < 0.001). Repeat incubation of Kupffer cells with lipopolysaccharide after prior lipopolysaccharide incubation induced low tumor necrosis factor-alpha release (tolerance). Repeat incubation with peptidoglycan-polysaccharide induced no tolerance to tumor necrosis factor-alpha release. Incubation of lipopolysaccharide plus peptidoglycan-polysaccharide released less tumor necrosis factor-alpha than did each polymer used alone, but this inhibition was prevented by indomethacin. Dibutyryl cyclic AMP, prostaglandin E1, prostaglandin E2 and the adenosine A2-receptor agonist N-ethylcarboxyamideadenosine inhibited lipopolysaccharide-stimulated tumor necrosis factor-alpha release by 83%, 97%, 90% and 94%, respectively, but inhibited peptidoglycan-polysaccharide-stimulated tumor necrosis factor-alpha release by 52%, 60%, 45% and 51%, respectively (p < 0.001 for each). This indicates that intracellular signaling pathways differ for lipopolysaccharide-stimulated and peptidoglycan-polysaccharide-stimulated tumor necrosis factor-alpha release. After incubation for 8 and 24 hr, 100 micrograms/ml peptidoglycan-polysaccharide had induced significantly more interleukin-1 release from cultured Kupffer cells than had 400 ng/ml lipopolysaccharide (p < 0.001). Lipopolysaccharide induced tolerance to interleukin-1 release after repeat incubation, but peptidoglycan-polysaccharide caused no tolerance. These studies show that peptidoglycan-polysaccharide, a ubiquitous bacterial cell wall polymer, shares several proinflammatory properties with lipopolysaccharide but that there are differences that may have pathophysiological significance.
内毒素（脂多糖）是革兰氏阴性菌的一种细胞壁聚合物，可刺激库普弗细胞释放细胞因子，如肿瘤坏死因子-α和白细胞介素-1。革兰氏阴性菌和革兰氏阳性菌中的另一种细菌细胞壁聚合物是肽聚糖-多糖。脂多糖和肽聚糖-多糖共同存在于肠腔中，可穿过肠黏膜，进入门静脉并激活库普弗细胞。本研究的目的是比较脂多糖刺激和肽聚糖-多糖刺激库普弗细胞对肿瘤坏死因子-α和白细胞介素-1释放的影响。两种细菌聚合物在孵育4至8小时后均引起库普弗细胞释放最大量的肿瘤坏死因子-α。400 ng/ml脂多糖诱导的最大肿瘤坏死因子-α释放量为704±258 pg/ml，而100 μg/ml肽聚糖-多糖作用后肿瘤坏死因子-α释放量为329±91 pg/ml（p<0.001）。多粘菌素B可使脂多糖刺激的肿瘤坏死因子-α释放减少95%±5%，但使肽聚糖-多糖刺激的肿瘤坏死因子-α释放减少30%±14%（p<0.001）。预先用脂多糖孵育库普弗细胞后再用脂多糖重复孵育，诱导的肿瘤坏死因子-α释放量较低（耐受性）。用肽聚糖-多糖重复孵育未诱导出对肿瘤坏死因子-α释放的耐受性。脂多糖加肽聚糖-多糖孵育后释放的肿瘤坏死因子-α比单独使用每种聚合物时少，但吲哚美辛可防止这种抑制作用。二丁酰环磷腺苷、前列腺素E1、前列腺素E2和腺苷A2受体激动剂N-乙基羧酰胺腺苷分别使脂多糖刺激的肿瘤坏死因子-α释放减少83%、97%、90%和94%，但使肽聚糖-多糖刺激的肿瘤坏死因子-α释放分别减少52%、60%、45%和51%（每种情况p<0.001）。这表明脂多糖刺激和肽聚糖-多糖刺激的肿瘤坏死因子-α释放的细胞内信号通路不同。孵育8小时和24小时后，100 μg/ml肽聚糖-多糖比400 ng/ml脂多糖诱导培养的库普弗细胞释放的白细胞介素-1显著更多（p<0.001）。脂多糖重复孵育后诱导对白细胞介素-1释放的耐受性，但肽聚糖-多糖未引起耐受性。这些研究表明，肽聚糖-多糖这种普遍存在的细菌细胞壁聚合物与脂多糖具有一些促炎特性，但也存在可能具有病理生理学意义的差异。
