TNF and periodontitis: Moreover, IL-1β in periodontal tissue was shown the lowest expression level in the TRAF-STOP/hydrogel treatment group (Figure 5C), which was consistent with the mRNA levels of IL-1β, IL-6, and TNF-α (Figure 5D), suggesting the combination of TRAF-STOP and hydrogel might be more effective than TRAF-STOP alone for the treatment of periodontitis.