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Kupffer cell activation by different microbial isolates: toll-like receptor-2 plays pivotal role on thromboxane A2 production
Kupffer cell activation by different microbial isolates: toll-like receptor-2 plays pivotal role on thromboxane A2 production
Background: Spontaneous bacterial peritonitis (SBP) is a bacterial infection that often occurs in patients with cirrhosis and can be fatal. Sinusoidal endothelial cells (SECs), Kupffer cells (KCs), and hepatic stellate cells (HSC) are major components of liver non-parenchymal cells. They play an important role in combating pathogenic bacteria, usually the earliest cells that come into contact with antigens. Thromboxane A2 (TXA2) was proved to be the critical vasoconstrictor secreted by activated KCs. Objection: We aimed to investigate the role of toll-like receptors (TLRs) in bacterial-induced TXA2 increase in liver nonparenchymal cells and to identify the most potent antagonists as potential therapeutic options in the future. Method: Primary nonparenchymal liver cells (including KCs, SECs, and HSCs) were isolated from mice, THP-1 macrophages (TMCs) differentiated by phorbol myristate acetate treatment and primary human KCs (HKCs) were investigated. Cells were characterized by immunostaining with special antibodies. Microbial isolates derived from patients with SBP and the special TLR-1 to -9 agonists were used to treat the related cells. TXB2, the stable degradation of TXA2, was measured in supernatants before and after stimulation. The special TLR-1/-2/-4 antagonists were additionally added in some experiments 1 h before stimulation. Result: TLR agonists only increased TXB2 in mouse KCs (MKCs) but not in SECs or HSCs. TLR-1, -2 and -4 rather than other agonists caused TXB2 increase in HKCs and MKCs, TLR-1 and -2 agonists also worked on TMCs. Pretreatment with TLR-1, -2 or -4 antagonist in HKCs significantly reduced the TXB2 increase caused by Gram-negative bacteria. TLR-1 and -2 antagonist also had effects on Gram-positive bacteria. Only Mab-mTLR2 worked on Candida albicans-induced TXB2 increase. Combination of TLR-1, -2 and -4 antagonists achieved a better effect. Conclusion: This is the first study to investigate the effect of human microbial isolates on the vasoconstrictor TXA2 after stimulation and activation of human KCs. TLR-1, -2 and -4 play an important role in bacterial-induced TXA2 secretion, the TLR-2 antagonist showed the most effective reduction in bacterial-induced TXA2 secretion. Therefore, TLR-2 might be a potential marker and an attractive target for the treatment of infections and liver cirrhosis.
toll-like receptor, spontaneous bacterial peritonitis, thromboxane A2, Kupffer cell, nonparenchymal liver cells
Zhang, Jiang
2019
English
Universitätsbibliothek der Ludwig-Maximilians-Universität München
Zhang, Jiang (2019): Kupffer cell activation by different microbial isolates: toll-like receptor-2 plays pivotal role on thromboxane A2 production. Dissertation, LMU München: Faculty of Medicine
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Abstract

Background: Spontaneous bacterial peritonitis (SBP) is a bacterial infection that often occurs in patients with cirrhosis and can be fatal. Sinusoidal endothelial cells (SECs), Kupffer cells (KCs), and hepatic stellate cells (HSC) are major components of liver non-parenchymal cells. They play an important role in combating pathogenic bacteria, usually the earliest cells that come into contact with antigens. Thromboxane A2 (TXA2) was proved to be the critical vasoconstrictor secreted by activated KCs. Objection: We aimed to investigate the role of toll-like receptors (TLRs) in bacterial-induced TXA2 increase in liver nonparenchymal cells and to identify the most potent antagonists as potential therapeutic options in the future. Method: Primary nonparenchymal liver cells (including KCs, SECs, and HSCs) were isolated from mice, THP-1 macrophages (TMCs) differentiated by phorbol myristate acetate treatment and primary human KCs (HKCs) were investigated. Cells were characterized by immunostaining with special antibodies. Microbial isolates derived from patients with SBP and the special TLR-1 to -9 agonists were used to treat the related cells. TXB2, the stable degradation of TXA2, was measured in supernatants before and after stimulation. The special TLR-1/-2/-4 antagonists were additionally added in some experiments 1 h before stimulation. Result: TLR agonists only increased TXB2 in mouse KCs (MKCs) but not in SECs or HSCs. TLR-1, -2 and -4 rather than other agonists caused TXB2 increase in HKCs and MKCs, TLR-1 and -2 agonists also worked on TMCs. Pretreatment with TLR-1, -2 or -4 antagonist in HKCs significantly reduced the TXB2 increase caused by Gram-negative bacteria. TLR-1 and -2 antagonist also had effects on Gram-positive bacteria. Only Mab-mTLR2 worked on Candida albicans-induced TXB2 increase. Combination of TLR-1, -2 and -4 antagonists achieved a better effect. Conclusion: This is the first study to investigate the effect of human microbial isolates on the vasoconstrictor TXA2 after stimulation and activation of human KCs. TLR-1, -2 and -4 play an important role in bacterial-induced TXA2 secretion, the TLR-2 antagonist showed the most effective reduction in bacterial-induced TXA2 secretion. Therefore, TLR-2 might be a potential marker and an attractive target for the treatment of infections and liver cirrhosis.