Lamichhane A, et al. J Adv Prosthodont. 2014 Feb;6(1):60-65. http://dx.doi.org/10.4047/jap.2014.6.1.60

Human periodontal ligament (PDL) cells underwent apoptosis after mechanical stretch loading. However, the exact signalling pathway remains unknown. This study aimed to elucidate how the apoptotic caspases functioned in the cyclic stretch-induced apoptosis in human PDL cells. In the present study, 20% cyclic stretch was selected to load the cells for 6 or 24 h. The following parameters were analyzed: apoptotic rates, the protein levels of caspase-3, -7, -8 and -9 and the activities of caspase-8 and -9. Subsequently, the influences of caspase-8 and caspase-9 inhibitors on the apoptotic rate and the protein level of the activated caspase-3 were assessed as well. The apoptotic rates increased in response to cyclic stretch, but the cells entered different apoptotic stages after 6 and 24 h stretches. Caspase-3, -7, -8 and -9 were all activated after stretch loading. The stretch-induced apoptosis and the protein level of the activated caspase-3 were inhibited after inhibiting both caspase-8 and caspase-9 in both 6 and 24 h stretched cells and after inhibiting caspase-9 in 24 h stretched cells. Caspase-8 and -9 functioned differently at different apoptotic stages in human PDL cells after cyclic stretch.

Activation of NLRP1 and NLRP3 inflammasomes contributed to cyclic stretch-induced pyroptosis and release of IL-1β in human periodontal ligament cells Activation of NLRP1 and NLRP3 inflammasomes contributed to cyclic stretch-induced pyroptosis and release of IL-1β in human periodontal ligament cells