Tissue inhibitor of metalloproteinases 1 is involved in ROS-mediated inflammation via regulating matrix metalloproteinase 1 expression in the sea cucumber Apostichopus japonicus

PPARα alleviates inflammation via inhibiting NF-κB/Rel pathway in Vibrio splendidus challenged Apostichopus japonicus

Organisms trigger pro-inflammatory responses to resist the invasion of foreign pathogens in the early infection stage. However, excessive or chronic inflammation can also cause several diseases. We previously validated IL-17 from sea cucumbers mediated inflammatory response by the IL-17R-TRAF6 axis. But the anti-inflammatory effect was largely unknown in the species. In this study, the conserved PPARα gene was obtained from Apostichopus japonicus by RNA-seq and RACE approaches. The expression of AjPPARα was found to be significantly induced at the late stage of infection not only in Vibrio splendidus-challenged sea cucumbers, but also in LPS-exposed coelomocytes, which was negative correlation to that of AjIL-17 and AjNLRP3. Both silencing AjPPARα by specific siRNA and treatment with AjPAPRα inhibitor MK-886 could significantly upregulate the transcriptional levels of pro-inflammatory factors the AjIL-17 and AjNLRP3. The infiltration of inflammatory cells and tissues damage were also detected in the body walls in the same condition. In contrast, AjPAPRα agonist of WY14643 treatment could alleviate the V. splendidus-induced tissue injury. To further explore the molecular mechanism of AjPPARα-mediated anti-inflammatory in A. japonicus, the expression of the transcriptional factors of AjStat5 and AjRel (subunit of NF-κB) were investigated under AjPPARα aberrant expression conditions and found that AjRel exhibited a negative regulatory relationship to AjPPARα. Furthermore, silencing AjRel was led to down-regulation of AjIL-17 and AjNLRP3. Taken together, our results supported that AjPPARα exerted anti-inflammatory effects through inhibiting AjRel in response to V. splendidus infection.

Possible Mechanisms of Stiffness Changes Induced by Stiffeners and Softeners in Catch Connective Tissue of Echinoderms

The catch connective, or mutable collagenous, tissue of echinoderms changes its mechanical properties in response to stimulation. The body wall dermis of sea cucumbers is a typical catch connective tissue. The dermis assumes three mechanical states: soft, standard, and stiff. Proteins that change the mechanical properties have been purified from the dermis. Tensilin and the novel stiffening factor are involved in the soft to standard and standard to stiff transitions, respectively. Softenin softens the dermis in the standard state. Tensilin and softenin work directly on the extracellular matrix (ECM). This review summarizes the current knowledge regarding such stiffeners and softeners. Attention is also given to the genes of tensilin and its related proteins in echinoderms. In addition, we provide information on the morphological changes of the ECM associated with the stiffness change of the dermis. Ultrastructural study suggests that tensilin induces an increase in the cohesive forces with the lateral fusion of collagen subfibrils in the soft to standard transition, that crossbridge formation between fibrils occurs in both the soft to standard and standard to stiff transitions, and that the bond which accompanies water exudation produces the stiff dermis from the standard state.