The mechanism of proprotein convertase subtilisin/kexin type 9 in the inflammatory response induced by Helicobacter pylori infection / 中华消化杂志

ABSTRACT

Objective:To explore the mechanism of proprotein convertase subtilisin/kexin type 9 (PCSK9) in the inflammatory response induced by Helicobacter pylori ( H. pylori) infection. Methods:From May 1, 2020 to January 31, 2021, 60 patients with gastritis (30 H. pylori positive and 30 H. pylori negative)and 30 healthy individuals, who initially visited the Department of Gastroenterology, Shiyan Taihe Hospital were collected, and their serum PCSK9 levels were detected. Normal gastric epithelial cell line GES-1 and macrophages induced from THP-1 cells, and GES-1 infected with H. pylori were selected to prepare different supernatant media. Phosphate buffer saline empty medium (negative control group), normal GES-1 cell supernatant medium ( H. pylori-uninfected GES-1 group), H. pylori infected GES-1 cell supernatant medium ( H. pylori infected GES-1 group), H. pylori infected GES-1 cell supernatant + PCSK9 neutralizing antibody medium (anti PCSK9 group), H. pylori infected GES-1 cell supernatant+ human immunoglobulin G medium (isotype control group) were established. The differences between H. pylori infected GES-1 group and H. pylori-uninfected GES-1 group, negative control group, anti PCSK9 group and isotype control group in number of migrated macrophages, relative expression level of CC chemokine receptor ( CCR2), the levels of released interleukin(IL)-6 and cell necrosis factor (TNF)- α, level of CD8 + T cell membrane phosphorylation, and the number of macrophage colonies were determined by Transwell assay, real time fluorescence quantitative polymerase chain reaction, plate colony assay, H. pylori and phagocytosis lysosome co-localization assay. The regulating mechanism of PCSK9 in H. pylori infection induced inflammation was analyzed. Independent sample t test was used for statistical analysis. Results:The serum level of PCSK9 of patients with H. pylori positive gastritis was higher than that of patients with H. pylori negative gastritis and healthy individuals ((384.00±57.57) g/L vs. (208.80±48.89) and (176.10±47.14) g/L), and the differences were statistically significant ( t=12.71 and 15.31; both P<0.001). Compared with negative control group, H. pylori standard strain and 4 isolated H. pylori strains could stimulate GES-1 to secrete PCSK9 ((1 267.00±287.50) g/L vs.(2 717.00±199.20), (4 858.00±302.40), (3 167.00±334.20), (6 075.00±597.30), (4 283.00±331.20) g/L), and the differences were statistically significant( t=10.15, 21.09, 10.56, 17.77, 16.85, all P<0.001). The number of migrated macrophages, CCR2 mRNA expression level in macrophage, expression levels of IL-6 and TNF-α, and the number of macrophage colonies of H. pylori-infected GES-1 group were all higher than those of H. pylori-uninfected GES-1 group and negative control group (132.20±5.67 vs.84.83±4.62, 39.83±4.12; 8.66±0.94 vs. 6.52±0.47 and 1.00±0.09, (281.00±8.56) ng/L vs. (115.00±7.72) and (64.00±5.44) ng/L, (619.80±18.47) ng/L vs.(373.30±12.85)and (225.70±6.44) ng/L, (357.00±16.31) colony forming unit (CFU) vs. (134.80±8.64) and (74.17±9.68) CFU), and the differences were statistically significant ( t=15.85, 32.27; 4.96, 19.79; 35.28, 52.43; 26.84, 49.37; 29.49, 36.53; all P<0.001). The percentage of co-localization of H. pylori and phagocytosis lysosome, and the expression of cell membrane CD3ζ Tyr142, granzyme B and perforin in CD8 + T cell of H. pylori-infected GES-1 group were lower than that of H. pylori-uninfected GES-1 group ((15.33±1.86)% vs. (34.50±3.72)% and (65.67±3.56)%, 464.20±120.80 vs. 1 924.00±262.10 and 2 390.00±484.10; (6.41±0.42)% vs.(17.37±0.73)% and (26.60±1.57)%; (6.84±1.37)% vs.(14.53±0.48)% and (26.22±1.21)%), and the differences were statistically significant( t=11.27 and 30.70, 12.39 and 9.45, 30.50 and 31.90, 25.96 and 13.00; all P<0.001). The number of migrated macrophages, the relative expression level of CCR2 mRNA, the expression levels of IL-6 and TNF-α, and the number of macrophage colonies of anti-PCSK9 group were all lower than those of isotype control group (72.50±4.97 vs. 128.30±6.74, 0.82±0.06 vs. 1.00±0.08, (85.50±4.37) ng/L vs. (277.70±8.98) ng/L, (291.80±13.69) ng/L vs. (615.30±12.65) ng/L, (111.50±10.21) CFU vs. (346.20±18.04) CFU), and the differences were statistically significant ( t=16.33, 4.40, 47.13, 42.50 and 27.73, all P<0.001). The percentage of co-localization of H. pylori and phagocytosis lysosome, the expression levels of CD3ζ Tyr142, granzyme B and perforin of anti-PCSK9 group were all higher than those of isotype control group ((51.05±3.03)% vs. (16.71±1.91)%, 2 948.00±384.00 vs. 1 156.00±178.60, (53.88±3.86)% vs. (5.88±0.93)%, (32.80±2.07)% vs. (6.83±0.54)%), and the differences were statistically significant ( t=23.49, 10.36, 29.60 and 29.76, all P<0.001). Conclusions:H. pylori can inhibit CD8 + T activation and cytotoxicity by inducing the release of PCSK9 from gastric epithelial cells, and can also recruit macrophages, activate nuclear factor-κB signal axis to up-regulate the level of released inflammatory factors from macrophages, inhibit the phagocytosis and killing effects of macrophages, so as to regulate the inflammatory response.