Elsevier

Leukemia Research

Volume 29, Issue 8, August 2005, Pages 915-922
Leukemia Research

Targeting cannabinoid receptors to treat leukemia: Role of cross-talk between extrinsic and intrinsic pathways in Δ9-tetrahydrocannabinol (THC)-induced apoptosis of Jurkat cells

https://doi.org/10.1016/j.leukres.2005.01.014Get rights and content

Abstract

Targeting cannabinoid receptors has recently been shown to trigger apoptosis and offers a novel treatment modality against malignancies of the immune system. However, the precise mechanism of apoptosis in such cancers has not been previously addressed. In this study, we used human Jurkat leukemia cell lines with defects in intrinsic and extrinsic signaling pathways to elucidate the mechanism of apoptosis induced by Δ9-tetrahydrocannabinol (THC). We observed that Jurkat cells deficient in FADD or caspase-8 were partially resistant to apoptosis, while dominant-negative caspase-9 mutant cells were completely resistant to apoptosis. Use of caspase inhibitors confirmed these results. Furthermore, overexpression of Bcl-2 rendered the cells resistant to THC at early time points but not upon prolonged exposure. THC treatment led to loss of Δψm, in both wild-type and FADD-deficient Jurkat cells thereby suggesting that THC-induced intrinsic pathway was independent of FADD. THC treatment of wild-type Jurkat cells caused cytochrome c release, and cleavage of caspase-8, -9, -2, -10, and Bid. Caspase-2 inhibitor blocked THC-induced caspase-3 in wild-type Jurkat cells but not loss of Δψm. Together, these data suggest that the intrinsic pathway plays a more critical role in THC-induced apoptosis while the extrinsic pathway may facilitate apoptosis via cross-talk with the intrinsic pathway.

Introduction

Although marijuana is popularly known as one of the oldest and most widely used drugs of abuse worldwide, its medicinal properties have been exploited for centuries [1]. Marijuana's major psychoactive component, Δ9-tetrahydrocannabinol (THC), is now believed to act through two main receptors: cannabinoid receptor (CB) 1, expressed mainly on cells of the central nervous system, and CB2, expressed primarily on cells of the immune system [1], [2], [3]. THC and other synthetic cannabinoids have been proposed as potential therapeutic agents in the treatment of pain, cachexia and nausea in AIDS and cancer therapy patients, as well as intraocular pressure due to glaucoma [1], [4]. Recently, the use of THC has also been suggested in the treatment of gliomas and prostate cancer [5], [6]. In addition, studies conducted in our laboratory have shown that various cannabinoids, both plant-derived and synthetic, can induce apoptosis in transformed immune cells, suggesting the potential use of cannabinoids in the treatment of cancers of immune origin [7]. We have shown that apoptosis in normal and transformed immune cells is mediated through CB2 [7], [8], although the precise signaling mechanism still remains to be established.

Apoptosis is primarily mediated through two pathways: the death receptor pathway and the mitochondrial pathway [9], [10], [11]. In the death receptor pathway, a death receptor ligand, such as Fas ligand, binds to its receptor, such as Fas, triggering aggregation of the death receptor, recruitment of an adaptor molecule, such as FADD, as well as pro-caspase-8 or -10 forming a complex named the death inducing signaling complex (DISC) [12]. This results in the autocatalytic cleavage and activation of caspase-8 or caspase-10, leading to activation of caspase-3 or -7 and induction of apoptosis [9]. In the mitochondrial pathway, cytochrome c is released from the mitochondria to form a complex called the apoptosome with apoptosis protease activator factor-1 (Apaf-1), dATP, and pro-caspase-9 [13], [14], [15], [16]. The apoptosome then activates caspase-9, which in turn activates caspase-3, thereby inducing apoptosis. In cells referred to as type I cells, the death receptor pathway and the mitochondrial pathway are distinct [17]. In type II cells, such as the widely studied transformed human Jurkat T cell line, the amount of caspase-8 or -10 activated by death receptor ligation is insufficient to activate caspase-3 [17]. Instead, caspase-8 or -10 cleaves Bid, a pro-apoptotic Bcl-2 family member, which then translocates to the mitochondria, triggering release of cytochrome c and recruitment of the mitochondrial pathway [18], [19].

In the current study, we used Jurkat cells to further investigate the pathways of apoptosis induced by THC. While the mitochondrial pathway was sufficient to induce apoptosis, it was facilitated by activation of the death receptor pathway through cross-talk and, interestingly, THC-induced apoptosis was regulated at least in part by caspase-2 and caspase-10.

Section snippets

Reagents

THC was obtained from the National Institute of Drug Abuse (Rockville, MD) and was initially dissolved in dimethyl sulfoxide (DMSO, Sigma, St. Louis, MO) to a concentration of 20 mM and stored at −20 °C. For experiments, THC was further diluted in RPMI 1640 (Invitrogen, Carlsbad, CA) medium free of fetal calf serum.

Cell lines

Wild-type (WT) Jurkat is an acute T-lymphoblastic leukemia cell line generated from a 14-year-old male. In addition, we used Jurkat cell lines that were deficient in signaling pathways

Effect of THC on wild-type Jurkat cells and those deficient in FADD, caspase-8 and caspase-9

In order to characterize the respective roles of the death receptor and the mitochondrial pathways in THC-induced apoptosis, we examined the effect of THC on wild-type, FADD-deficient, caspase-8 deficient, and caspase-9 dominant negative Jurkat cells. As shown in Fig. 1a, after 3 h of incubation with THC at a concentration of 10 μM, there was 61.3% apoptosis in wild-type Jurkat cells, which was similar to the amount of apoptosis found in wild-type Jurkat cells incubated with membrane bound FasL,

Discussion

Recently, THC has been shown to induce apoptosis in a variety of cells [5], [6], [7], [8], although the precise mechanisms remain unclear. In the current study, we used Jurkat cells, which were shown to undergo apoptosis following exposure to THC [7], to further investigate the pathways of apoptosis. Treatment of wild-type Jurkat cells with THC triggered the extrinsic (death receptor) pathway of apoptosis, which was evidenced by the fact that THC treatment led to activation of caspase-8 and

Acknowledgment

This work was supported in part by National Institutes of Health grants.

References (40)

Cited by (58)

  • Cannabinoid-mediated targeting of mitochondria on the modulation of mitochondrial function and dynamics

    2023, Pharmacological Research
    Citation Excerpt :

    Cannabinoids induce apoptosis primarily through the activation of the intrinsic apoptotic signalling pathway (also known as the mitochondrial pathway), which is associated with the dysregulation of the Bcl-2 family of proteins, which in turn leads to mitochondrial dysfunction (i.e. depolarization and ROS production) and subsequent release of pro-apoptotic mitochondrial proteins (e.g., cytochrome c, serine protease OMI/HtrA2, endonuclease G and Smac/Diablo) into the cytosol [81–83]. Lombard et al. (2005) demonstrated that a 3 h exposure of Jurkat cells to 10 μM Δ9-THC induced apoptosis primarily through the activation of the intrinsic pathway, as evidenced by the increased cleavage of Bid (pro-apoptotic protein of the Bcl-2 family), loss of mitochondrial membrane potential and the release of cytochrome c into the cytosol [84]. Cytosolic cytochrome c then promoted the cleavage of caspases-2 and − 9 (two key effector caspases in the mitochondrial pathway), which in turn led to cell death.

  • THC shows activity against cultured Plasmodium falciparum

    2021, Bioorganic and Medicinal Chemistry Letters
  • The tamoxifen derivative ridaifen-B is a high affinity selective CB <inf>2</inf> receptor inverse agonist exhibiting anti-inflammatory and anti-osteoclastogenic effects

    2018, Toxicology and Applied Pharmacology
    Citation Excerpt :

    Mechanisms underlying the cytotoxic effect of RID-B in these cancer types include induction of apoptosis, activation of caspases-3, -8, and -9, and disruption of mitochondrial membrane potential. Similarly, the cannabinoids Δ9-tetrahydrocannabinol (Δ9-THC) and cannabidiol produce apoptosis of lymphoma and leukemia cell lines via disruption of mitochondrial membrane potential (Lombard et al., 2005; Mckallip et al., 2006). Furthermore, RID-B induces autophagy in the ER-negative Jurkat T-cell lymphoma cancer cell line, independent of the conventional Beclin 1 autophagy pathway (Nagahara et al., 2013).

View all citing articles on Scopus
View full text