Background:
Thromboxane A2 (TXA2; the stable degradation product is thromboxane B2) was identified as an important vasoconstrictor upon Kupffer cell (KC) activation via Toll-like receptors (TLRs).
Objectives:
We aimed at investigating the relevant TLRs on KCs activated by different microbial products.
Methods:
THP-1 cell line and primary KC isolated from human tissues (HKC, tissues from HTCR foundation) or mice (MKC) were investigated. Thromboxane B2 (TXB2) in supernatants was measured after 24h stimulation by TLR 1 – 9 agonists or bacterial isolates [Klebsiella pneumoniae (KLPN), Escherichia coli (E. coli), Enterobacter cloacae (ENCL), Enterococcus faecium (ENCF), Streptococcus pneumoniae (STPN), Staphylococcus aureus (STAU) and Candida albicans (CAAL), each 8 µg/ml]. The special TLR antagonists (CU-CPT22, 10µM; Mab-mTLR2, 1 µg/ml and TAK-242, 1µM) were additionally investigated.
Results:
All cell types were characterized by immunostaining. Stimulation with microbial products increased TXB2 efflux in THP-1, HKCs and MKCs (for HKCs see according figure).
TLR1, 2 and 4 agonists also increased TXB2 efflux on different kinds of KCs: TLR1 149 ± 26 vs. 267 ± 130*, 6380 ± 5357 vs. 127004 ± 150292* and 21 ± 13 vs. 88 ± 58*; TLR2 122 ± 36 vs. 1399 ± 681*, 5724 ± 1649 vs. 281468 ± 358872* and 74 ± 40 vs. 336 ± 199*; TLR4 136 ± 40 vs. 117 ± 28, 8782 ± 6931 vs. 106933 ± 110249* and 48 ± 32 vs. 231 ± 120* pg/ml each in THP-1 cells, HKCs and MKCs. The other TLR agonists had no effect on TXB2 production.
Additional 1h pretreatment with TLR1, 2 or 4 antagonist in HKCs reduced the TXB2 increase by E. coli, ENCF and STPN.
Abb. 1:
Fig-HKC&bacteria
Conclusions:
This is the first study describing the increase of the vasoconstrictor TXB2 following activation of human KCs with different, clinically relevant human microbial isolates. These results might improve individual medical treatment e.g. using specific inhibition for TLR 2 on patients with liver diseases and portal hypertension triggered by microbes.
