Tsunoda, M. | bioRxiv Science

bioRxiv2021

Role of TLR4 signaling on Porphyromonas gingivalis LPS-induced cardiac dysfunction in mice

Oral infections, particularly periodontitis, are a well-established risk factor for cardiovascular diseases, although the molecular mechanisms involved remain elusive. The aims of the present study were to investigate the effects of lipopolysaccharide derived from Porphyromonas gingivalis (PG-LPS) on cardiac function in mice, and to elucidate the underlying mechanisms. Mice (C57BL/6) were injected with PG-LPS (0.8 mg/kg/day) with or without an inhibitor of Toll-like receptor 4 (TLR4) signaling (TAK-242, 0.8 mg/kg/day) for 4 weeks. Left ventricular ejection function was significantly decreased at 1 week (from 67 {+/-} 0.5 to 58 {+/-} 1.2 %) and remained low at 4 weeks (57 {+/-} 1.0 %). The number of apoptotic myocytes was increased (approximately 7.4-fold), the area of fibrosis was increased (approximately 3.3-fold) and the number of 8-hydroxydeoxyguanosine-positive myocytes, a sensitive indicator of oxidative DNA damage, was increased (approximately 7.6-fold) at 4 weeks in the heart of PG-LPS treated mice. However, levels of various serum pro-inflammatory cytokines in PG-LPS-treated mice were similar to those in control mice. The impairment of cardiac function in PG-LPS-treated mice appears to involve activation of TLR4-NADPH oxidase (NOX) 4 signaling, leading to abundant production of reactive oxygen species and Ca2+ leakage from sarcoplastic reticulumn induced by calmodulin kinase II (CaMKII)-mediated phosphorylation of phospholamban (at Thr-17) and ryanodine receptor 2 (at Ser-2448). Pharmacological inhibition of TLR4 with TAK-242 attenuated the changes in cardiac function in PG-LPS-treated mice. Our results indicate that TLR4-NOX4 signaling may be a new therapeutic target for treatment of cardiovascular diseases in patients with periodontitis.

physiology↗

bioRxiv2021

T cell receptor (TCR) repertoire analysis reveals a highly conserved TCR repertoire in a bilateral tumor mouse model

Temporal analysis of the T cell receptor (TCR) repertoire has been used to monitor treatment-induced changes in antigen-specific T cells in patients with cancer. However, the lack of experimental models that allow temporal analysis of the TCR repertoire in the same individual in a homogeneous population limits the understanding of the causal relationship between changes in TCR repertoire and antitumor responses. A bilateral tumor model, where tumor cells were inoculated bilaterally into the backs of mice, could be used for temporal analysis of the TCR repertoire. This study examined the prerequisite for this strategy: the TCR repertoire is conserved between bilateral tumors with the same growth rate. Bilateral tumors with equivalent size and draining lymph nodes (dLNs) were collected 13 days after tumor inoculation to analyze the TCR repertoire of CD4+ and CD8+ T cells. The tumor-infiltrating T cell clones were highly conserved between the bilateral tumors, and the extent of clonal expansion was equivalent. In addition, the similarity between the bilateral tumors was equivalent to heterogeneity on one side of the tumor. The similarity of the TCR repertoire in the bilateral dLNs was markedly lower than that in the tumor, suggesting that tumor-reactive T cell clones induced independently in each dLN integrated during recirculation and then infiltrated the tumor. These findings suggest that our bilateral tumor model is suitable for temporal monitoring of the TCR repertoire to evaluate temporal and treatment-induced changes in tumor-reactive T cell clones. Significance StatementThe bilateral subcutaneous tumor model, where tumor cells were inoculated bilaterally into the backs of mice, is a promising model for temporal analysis of the antitumor response in cancer immunotherapy. This study demonstrated a highly conserved TCR repertoire in bilateral tumors and provided the basis for using a bilateral tumor model for evaluating temporal and treatment-induced changes in tumor-responsive T cell clones in individual mice. In humans, accurate statistical analysis is hampered by various background factors, including cancer type and stage and history of treatment. Moreover, temporal tumor biopsy in patients is highly invasive. Our bilateral tumor model overcomes these clinical issues and is expected to be a valuable tool for the development of novel immune monitoring and therapeutic strategies.

immunology↗