Correlation Analysis of TAM Subfamily of Receptor Tyrosine Kinases in Ulcerative Colitis / 胃肠病学

Background: TAM receptors (Tyro3, Axl and Mertk), as subfamily of receptor tyrosine kinases, are intracellular negative feedback regulators and play a crucial role in regulating inflammation and immune response. Aims: To study the expressions and clinical value of TAM receptors in serum and intestinal mucosa of patients with ulcerative colitis (UC). Methods: Forty⁃five patients who were initially diagnosed as active UC from June, 2020 to May, 2021 at the First Affiliated Hospital of Kunming Medical University were enrolled prospectively. Fifteen healthy subjects were served as the control group. Eight cases each in moderate UC group and healthy control group were selected randomly for detection of TAM receptors in serum and intestinal mucosa by ELISA, real⁃time PCR and Western blotting. The correlations of serum Tyro3 with routine clinical indicators of UC were analyzed by Pearson correlation coefficient. Furthermore, immunohistochemistry was used to detect the expression level of TAM receptors in intestinal mucosa in all UC patients and the healthy controls. Results: Expressions of Axl and Mertk were not fully consistent in serum and intestinal mucosa in UC patients. While the serum Tyro3 level, as well as the intestinal Tyro3 mRNA and protein expressions were consistently increased in moderate UC patients than in controls (all P<0.05). Serum level of Tyro3 was positively correlated with platelet count and C⁃reactive protein, and negatively correlated with albumin in moderate UC patients (r=0.97, r=0.96, r=-0.86, all P<0.05). Positivity rate of Tyro3 in intestinal mucosa of UC patients was positively correlated with the disease severity (all P<0.05). Conclusions: Tyro3 is closely related to UC and positively correlated with the disease severity. It might be a promising novel molecular marker and therapeutic target of UC.

Association between Genetic Variations of MERTK and Chronic Obstructive Pulmonary Disease in Koreans

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a debilitating lung disease. To date, a large number of clinical studies have been conducted to investigate the association between genetic variations and COPD. However, little is known regarding the genetic susceptibility of Koreans to this disease. MER receptor tyrosine kinase (MERTK) plays important roles in the inhibition of inflammation and in the clearance of apoptotic cells. Here, we investigated the association between genetic variations in MERTK and the development of COPD in Koreans. METHODS: We conducted genetic analysis of MERTK using genomic DNA samples from 87 patients with COPD and 88 healthy controls and compared the frequency of each variation or haplotype between the patient and control groups. Subsequently, the effect of each variation was evaluated using in vitro assays. RESULTS: Ten variations were identified in this study, four of them for the first time. In addition, we found that the frequency of each variation or haplotype was comparable between the patient and control groups. However, we observed that the frequency for the wild-type haplotype was higher in the control group, compared to that in the group of patients with COPD, in the subgroup analysis of current smokers, although the difference was not statistically significant (P = 0.080). In in vitro assays, we observed that none of the variations affected the activity of the promoter or the expression of MERTK. CONCLUSION: Our findings indicate that the susceptibility to COPD is not related to the genetic variations or haplotypes of MERTK in Koreans.

The role of receptor protein tyrosine kinase MERTK and intracellular Ca2+ playing in the phagocytosis of human retinal pigment epithelial cells / 中华眼底病杂志

Objective To investigate the role of intraeellular Ca2+ and MERTK in the phagocytosis of human retinal pigment epithelial (RPE) cells, and reveal the relationship between MERTK and intraeellular Ca2+. Methods The euhured RPE cells were incubated with rod outer segments (ROS) at 37℃, the phagoeytosis was terminated at different incubation time points. The concentration of intraeellular Ca2+ was assayed by Fluro-3/AM loading methods combined with fluorescence microscope and CCD system, and the mRNA level of MERTK gene was measured by reverse transcription polymerase chain reaction (RT-PCR). Treating the RPE cells with stimulator (A23187)or inhibitor(verapamile)of intraeellular Ca2+ to observe the changes of MERTK gene expression. Results ROS adhered to hRPE cells at the 15th minute, and the ingestion saturated at the 24th hour. The concentration of intracellular Ca2+ increased at the 15th minute, and kept the high level in 24 hours. The level of MERTK mRNA increased at the 5th minute, and kept the high level duration the whole incubation. When RPE cells were treated by A23187, the expression of MERTK increased in a dose-dependent manner. After RPE cells was pretreated by A23187, the expression level of MERTK was higher in the proceeding incubation groups than which in the control group except at the 3rd hour. When RPE cells were treated by verapamil, the expression level of MERTK decreased in a dose-dependent manner. After RPE cells were pretreated by verapamil , the expression level of MERTK was lower in all the proceeding incubation groups than which in the control group (P<0.05). Conclusion MERTK gene and Ca2+ play an important role in sustaining RPE cells phagoeytizing ROS. As an up-stream regulator, the receptor tyrosine kinase MERTK keeps RPE cells phagocytizing ROS by starting the intracellular Ca2+.