Skeletal Muscle Myofibers Directly Contribute to LPS-Induced Systemic Inflammatory Tone

Association Between Plasma Levels of Monocyte Chemoattractant Protein-1 (MCP-1) and 28-Day Mortality in Elderly Patients with Sepsis: A Retrospective Single-Center Study

BACKGROUND Previous studies have identified an association between plasma levels of the inflammatory cytokine, monocyte chemoattractant protein-1 (MCP-1), and outcomes for patients with sepsis. This retrospective single-center study assessed the association between plasma levels of MCP-1 and 28-day mortality in 136 patients ≥65 years diagnosed with sepsis between October 2020 and October 2021. MATERIAL AND METHODS The objective was to compare and analyze the parameters in the survival group (n=35) and the 28-day mortality group (n=101), including Sequential Organ Failure Assessment (SOFA), Acute Physiology and Chronic Health Evaluation II (APACHE II), plasma MCP-1, and laboratory test results. Plasma MCP-1 was quantified by cytokine test kit (LKTM014B, R&D). Statistical analysis was carried out in SPSS 26.0 and MedCalc 92.1.0 software. RESULTS The 28-day mortality group exhibited higher levels of SOFA, APACHEII, and plasma MCP-1 (all P<0.001), as well as lower levels of albumin, compared to the survival group (P<0.05). The logistic regression analysis findings indicated that SOFA, APACHEII, plasma MCP-1, and SBP are all independent risk factors for 28-day mortality. The area under the curve for SOFA, APACHEII, MCP-1, MCP-1+ SOFA, and MCP-1+APACHEII were 0.845, 0.744, 0.712, 0.879, and 0.822, respectively. MCP-1+SOFA exhibited higher sensitivity than SOFA alone. Furthermore, the assessment values of plasma MCP-1 combined with SOFA were superior to those of APACHE II or plasma MCP-1 (Z₁=2.661, Z₂=3.272, both P<0.01). CONCLUSIONS The findings from this study from a single center support those of previous studies that increased plasma levels of MCP-1 are significantly associated with 28-day mortality in patients with sepsis.

Secretion of Interleukin 6 in Human Skeletal Muscle Cultures Depends on Ca2+ Signalling

The systemic effects of physical activity are mediated by the release of IL-6 and other myokines from contracting muscle. Although the release of IL-6 from muscle has been extensively studied, the information on the cellular mechanisms is fragmentary and scarce, especially regarding the role of Ca²⁺ signals. The aim of this study was to characterize the role of the main components of Ca²⁺ signals in human skeletal muscle cells during IL-6 secretion stimulated by the Ca²⁺ mobilizing agonist ATP. Primary cultures were prepared from surgical samples, fluorescence microscopy was used to evaluate the Ca²⁺ signals and the stimulated release of IL-6 into the medium was determined using ELISA. Intracellular calcium chelator Bapta, low extracellular calcium and the Ca²⁺ channels blocker La³⁺ reduced the ATP-stimulated, but not the basal secretion. Secretion was inhibited by blockers of L-type (nifedipine, verapamil), T-type (NNC55-0396) and Orai1 (Synta66) Ca²⁺ channels and by silencing Orai1 expression. The same effect was achieved with inhibitors of ryanodine receptors (ryanodine, dantrolene) and IP3 receptors (xestospongin C, 2-APB, caffeine). Inhibitors of calmodulin (calmidazolium) and calcineurin (FK506) also decreased secretion. IL-6 transcription in response to ATP was not affected by Bapta or by the T channel blocker. Our results prove that ATP-stimulated IL-6 secretion is mediated at the post-transcriptional level by Ca²⁺ signals, including the mobilization of calcium stores, the activation of store-operated Ca²⁺ entry, and the subsequent activation of voltage-operated Ca²⁺ channels and calmodulin/calcineurin pathways.