Increased N-Acetyltaurine in the Skeletal Muscle After Endurance Exercise in Rat.

Taurine is metabolized to a novel metabolite, N-acetyltaurine (NAT), through N-acetylation with acetate. Furthermore, NAT production increases when the endogenous production of acetate is elevated in some situations, such as alcohol catabolism and endurance exercise. We have previously reported that both the serum concentration and urinary excretion of NAT from humans were increased after endurance exercise, and that NAT was secreted by cultured skeletal muscle cells exposed to both acetate and taurine. The present study evaluated the hypothesis that NAT is synthesized in the skeletal muscle after endurance exercise. Normal rats were loaded to a transient treadmill running until exhaustion. Serum, skeletal muscle, and liver were collected immediately after the exercise. The NAT concentration in the plasma and in the soleus muscle from the exercised rats was significantly increased compared to that in the samples from the sedentary control rats. There was a significant positive correlation in the NAT concentration between the plasma and soleus muscle. The NAT concentration in the liver was unchanged after the endurance exercise. These results confirm that the significantly increased NAT in both the serum and urine after endurance exercise is derived from NAT synthesis in the skeletal muscle.

TX99 Is a Neutralizing Monoclonal Antibody Against Mouse TIGIT.

T cell immunoglobulin and ITIM domains (TIGIT) is an inhibitory immunoreceptor expressed on NK cells, effector and memory T cells, and regulatory T cells (Tregs). The ligands for TIGIT are CD155 (PVR) and CD112 (PVRL2, nectin-2), which are broadly expressed on hematopoietic cells and nonhematopoietic cells. TIGIT negatively regulates antitumor responses, but promotes autoimmune reaction. Although neutralizing anti-human TIGIT mAbs are under clinical trials for cancers, how the blockade of TIGIT interaction with the ligands shows tumor immunity still remains unclear. Although analyses of mouse tumor model using a neutralizing anti-mouse TIGIT (mTIGIT) mAbs should be useful to address this issue, there are limitations to this type of studies due to unavailability of neutralizing anti-mTIGIT mAbs. In this study, we generated five clones of anti-mTIGIT mAbs, designated TX99, TX100, TX103, TX104, and TX105. We show that TX99 and TX100 showed the strongest binding to TIGIT. We also show that TX99 interfered with the interaction between TIGIT and CD155 and increased NK cell-mediated cytotoxicity against CD155-expressing RMA-S cells. Thus, TX99 is a unique neutralizing mAb that can be used for studies of mTIGIT functions.