The Human Host Defense Peptide LL-37 Induces Apoptosis in a Calpain- and Apoptosis-Inducing Factor–Dependent Manner Involving Bax Activity

Abstract

LL-37 is a human cationic host defense peptide (antimicrobial peptide) belonging to the cathelicidin family of peptides. In this study, LL-37 was shown to kill Jurkat T leukemia cells via apoptosis. A loss of mitochondrial membrane potential, DNA fragmentation, and phosphatidylserine externalization were detected following LL-37 exposure, whereas apoptosis was independent of caspase family members. The specific apoptotic pathway induced by LL-37 was defined through the utilization of Jurkat cells modified to express antiapoptotic proteins, as well as cells deficient in various proteins associated with apoptosis. Of interest, both Bcl-2-overexpressing cells and cells deficient in Bax and Bak proteins displayed a significant reduction in LL-37-induced apoptosis. In addition, Jurkat cells modified in the Fas receptor-associated pathway showed no reduction in apoptosis when exposed to LL-37. Analysis of the involvement of apoptosis-inducing factor (AIF) in LL-37-mediated apoptosis revealed that AIF transferred from the mitochondria to the nucleus of cells exposed to LL-37, where it may lead to large-scale DNA fragmentation and chromatin condensation. AIF knockdown analysis resulted in LL-37-resistant cells. This suggests that AIF is mandatory in LL-37-mediated killing. Lastly, chelation or inhibition of Ca 2+ or calpains inhibited LL-37-mediated killing. Further analysis revealed that calpains were required for LL-37-mediated Bax translocation to mitochondria. Together, these data show that LL-37-induced apoptosis is mediated via the mitochondria-associated pathway in a caspase-independent and calpain-and AIF-dependent manner that involves Bax activation and translocation to mitochondria. (Mol Cancer Res 2009;7(5):689-702)

The Human Cathelicidin, LL-37, Induces Granzyme-mediated Apoptosis in Regulatory T Cells

“…An earlier paper published by our laboratory analyzed the mechanism of apoptosis induced in Jurkat T leukemia cells exposed to LL-37. 33 We found that Jurkat cells were killed by higher concentrations of LL-37 (50 to 200 mg/mL), through a calpain-dependent and apoptosis inducing factor-dependent pathway requiring the Bcl-2 family member, BAX.…”

“…This may be due to the activation of cell death pathways that are not reliant on grA or B, such as the calpain-dependent mechanism previously described. 33 In this earlier study, higher concentrations of LL-37 (100 mg/mL) were required to induce apoptosis in cell lines such as Jurkat. Activation of calpain and the release of apoptosis inducing factor from mitochondria were found to be critical in the demise of the cell.…”

“…In other cell types, this level of fragmentation required 100 to 200 mg/mL. 33 It was determined that Tregs exposed to LL-37 died through the induction of apoptosis, characterized by DNA fragmentation and chromatin condensation (Figs. 1A-C).…”

The random co-polymer glatiramer acetate rapidly kills primary human leukocytes through sialic-acid-dependent cell membrane damage

“…Accordingly, it seemed appropriate to test both compounds for one of the known influences of LL-37 on cells, namely its cell toxicity (31)(32)(33)(34). As a starting point, we chose concentrations of GA and LL-37 of 2-50 µg/ml, similar to the range used by Koenig et al for GA stimulation of cytokine production by RAW264.7 and murine bone-marrow-derived dendritic cells (12).…”

Roles and Mechanisms of Human Cathelicidin LL-37 in Cancer

“…Notably, recombinant LL-37 treatment reportedly kills Jurkat T leukemia cells by activating apoptosis that is caspase-independent but calpain-and AIF-dependent as shown by BAX activation and translocation to mitochondria (Fig. 5) [2,88]. Although LL-37 targeted receptor in Jurkat cells has not yet been reported, it is known that FPRL1, a LL-37-targeted GPCR is expressed in T lymphocytes [89].…”