Thapsigargin Increases IL-2 Production in T Cells at Nanomolar Concentrations

7-Hydroxy Frullanolide, a sesquiterpene lactone, increases intracellular calcium amounts, lowers CD4+ T cell and macrophage responses, and ameliorates DSS-induced colitis

Sesquiterpene lactones are a class of anti-inflammatory molecules obtained from plants belonging to the Asteraceae family. In this study, the effects of 7-hydroxy frullanolide (7HF), a sesquiterpene lactone, in inhibiting CD4⁺ T cell and peritoneal macrophage responses were investigated. 7HF, in a dose dependent manner, lowers CD69 upregulation, IL2 production and CD4⁺ T cell cycling upon activation with the combination of anti-CD3 and anti-CD28. Further mechanistic studies demonstrated that 7HF, at early time points, increases intracellular Ca²⁺ amounts, over and above the levels induced upon activation. The functional relevance of 7HF-induced Ca²⁺ increase was confirmed using sub-optimal amounts of BAPTA, an intracellular Ca²⁺ chelator, which lowers lactate and rescues CD4⁺ T cell cycling. In addition, 7HF lowers T cell cycling with the combination of PMA and Ionomycin. However, 7HF increases CD4⁺ T cell cycling with sub-optimal activating signals: only PMA or anti-CD3. Furthermore, LPS-induced nitrite and IL6 production by peritoneal macrophages is inhibited by 7HF in a Ca²⁺-dependent manner. Studies with Ca²⁺ channel inhibitors, Ruthenium Red and 2-Aminoethoxydiphenyl borate, lowers the inhibitory effects of 7HF on CD4⁺ T cell and macrophage responses. In silico studies demonstrated that 7HF binds to Ca²⁺ channels, TRPV1, IP3R and SERCA, which is mechanistically important. Finally, intraperitoneal administration of 7HF lowers serum inflammatory cytokines, IFNγ and IL6, and reduces the effects of DSS-induced colitis with respect to colon length and colon damage. Overall, this study sheds mechanistic light on the anti-inflammatory potential of 7HF, a natural plant compound, in lowering immune responses.

Sarco/Endoplasmic Reticulum Calcium ATPase Inhibitors: Beyond Anticancer Perspective

The sarco/endoplasmic reticulum calcium ATPase (SERCA), which plays a key role in the maintenance of Ca²⁺ ion homeostasis, is an extensively studied enzyme, the inhibition of which has a considerable impact on cell life and death decision. To date, several SERCA inhibitors have been thoroughly studied and the most notable one, a derivative of the sesquiterpene lactone thapsigargin, is gradually approaching a clinical application. Meanwhile, new compounds with SERCA-inhibiting properties of natural, synthetic, or semisynthetic origin are being discovered and/or developed; some of these might also be suitable for the development of new drugs with improved performance. This review brings an up-to-date comprehensive overview of recently discovered compounds with the potential of SERCA inhibition, discusses their mechanism of action, and highlights their potential clinical applications, such as cancer treatment.