Pharmacological inhibition of the NLRP3 inﬂammasome as a potential target for cancer-induced bone pain

doi:10.1016/j.phrs.2019.104339

Pharmacological Research

Volume 147, September 2019, 104339

https://doi.org/10.1016/j.phrs.2019.104339 Get rights and content

Abstract

Cancer-induced bone pain (CIBP) remains a major challenge in patients suffering from bone metastases because of the complex mechanisms and unsatisfactory treatments. Emerging evidence have shown that activation of inflammasomes contribute to the development of inflammatory and neuropathic pain. However, the role of spinal inflammasomes in CIBP remains unclear. In the present study, we explored the specific cellular mechanisms of NLRP3 inflammasome in the process of CIBP in rats. MCC950 is a small molecule inhibitor of the NLRP3 inflammasome that exhibits remarkable activity in inflammatory diseases. Our behavioral results confirmed that both single and persistent treatment with MCC950 markedly attenuated CIBP-related mechanical allodynia. The expression of NLRP3 inflammasome, including NLRP3, ASC, Caspase-1, were significantly increased in a time-dependent manner. Furthermore, spinal IL-1β, cleaved by cysteine-aspartic acid protease, was upregulated in this study. Chronic administration with MCC950 restored the protein expression of NLRP3 inflammasome and significantly suppressed the upregulation of IL-1β. Spinal NLRP3 inflammasome might be a novel therapeutic target for treatment of CIBP.

Graphical abstract

Introduction

Cancer-induced bone pain (CIBP) is a serious symptom for patients with advanced breast, lung, and prostate cancer [1,2]. In epidemiological studies, up to 90% of end-stage cancer patients experience chronic pain syndromes [3,4]. Although there are many basic and clinical studies, the exact mechanisms involving bone pain remain elusive [5]. Therefore, it is necessary to further clarify the mechanisms of CIBP and find more effective pharmacological treatments.

Multiple bodies of evidence show that numerous inflammatory cytokines involve in the development of pain by acting on nociceptors, including tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 [[6], [7], [8]]. IL-1β, one of the most important pro-inflammatory cytokines, is responsible for the induction and development of inflammatory pain [9,10]. Several lines of studies confirm that IL-1β is involved in the process of neuropathic pain [11,12]. Substantial studies mention that IL-1β possesses biological activity only after proteolysis by cysteine protease [[13], [14], [15]]. Recently, inflammasomes are reported to regulate the maturation of IL-1 family as a multi-protein complex platform [16,17]. Inflammasome complexes consist of intracellular nucleotide-binding oligomerization domain–like receptors (NLRs), the adapter molecule apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain (ASC), and pro-caspase-1, pro-caspase-5, or both [18,19]. Evidence is accumulating that caspase-1 is the well-known cysteine protease involved in the processing of IL-1β [14,20]. Moreover, other studies suggest that inflammasomes participate in the development of inflammatory diseases, cancers, pain, and metabolic disorders [9,18,21]. Inflammasomes are generally divided into four types, including leucine-rich repeat and pyrin domain containing protein 1 (NLRP1), leucine-rich repeat and pyrin domain containing protein 3 (NLRP3), NLR family CARD domain-containing protein 4 (NLRC4), and absent in melanoma 2 (AIM2). NLRP3 inflammasomes, the most described inflammasomes, were shown to be activated by diverse ligands and stimuli, such as ATP, low intracellular K⁺, and high extracellular glucose [[22], [23], [24]]. Once activated by microbial- or danger-associated molecular patterns, NLRP3 recruits ASC and pro-caspase-1, which promotes the release and maturation of several pro-inflammatory cytokines, including IL-1β, IL-18,and TNF-α [25,26]. Electroacupuncture is reported to inhibit NLRP3 inflammasomes activation through CB2 receptors to alleviate the inflammatory pain [27]. In a mouse model of neuropathic pain, peptide5 effectively attenuates mechanical pain via suppressing NLRP3 inflammasomes [28]. Bay11-7082, a selective inhibitor of IKK-β, reduces NF-κB and NLRP3 inﬂammasome activation along with attenuation of the pain in rat model of lumbar disc herniation [29]. However, the role of NLRP3 inflammasomes in CIBP remains yet to be elucidated.

Recently, a potent and selective inhibitor of NLRP3 inflammasome, MCC950, was described with early promise for treatment of inflammatory diseases [30]. MCC950 is a diarylsulphonylurea-containing compound that was reported to reduce ATP + LPS-induced mature IL-1β production in monocytes and macrophages [31]. Here, we explored whether the NLRP3 inflammasomes would be implicated in the rat model of CIBP. Firstly, we demonstrated the cellular expression of NLRP3 inflammasomes in spinal cord and the MCC950 (a selective NLRP3 inhibitor) effect. Then, we confirmed whether the analgesic effect of MCC950 was mediated by NLRP3 inflammasomes. Our results demonstrated that the activation of NLRP3 inflammasomes played a significant role in the process of CIBP. Moreover, pharmacological inhibition of the NLRP3 inﬂammasomes could be a novel strategy to alleviate the CIBP.

Section snippets

Animals and ethics statement

In this study, we chose virgin female Sprague Dawley rats (180–200 g, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People’s Republic of China). All animals were housed under a 12 h light/dark cycle with food and water available ad libitum. All experimental protocols were approved by the Animal Care and Use Committee of Huazhong University of Science & Technology and followed the policies issued by the guidelines for pain research of the International Association

MCC950, a selective NLRP3 inhibitor, relieved CIBP-induced mechanical allodynia

To evaluate the development of mechanical allodynia, ipsilateral PWTs were recorded at baseline and day 3, 7, 14 and 21 after TCI (tumor cell implantation). Among all groups, the baseline PWTs were similar. Consistent with our previous studies [36], the PWTs of CIBP rats were significantly decreased from day 7 to day 21, compared with the sham and naïve group (Fig. 1A). These findings testified that mechanical allodynia was developed after injection of Walker 256 cells.

To investigate the role

Discussion

In the present study, we demonstrated that: (1) inhibition of NLRP3 inflammasome via i.p treatment of MCC950, a selective NLRP3 inhibitor, markedly alleviated CIBP-related mechanical allodynia, (2) After TCI, the expression of NLRP3 inflammasome were upregulated in the spinal cord, including NLRP3, ASC, and Caspase-1, (3) inoculation of Walker 256 cells induced upregulation of spinal IL-1β in a time-dependent manner, (4) Chronic treatment of MCC950 suppressed the activation of NLRP3

Acknowledgements

This work was supported by grants from National Natural Science Foundation of P.R. China (Grant Nos. 81873732, 81371250, 81571053, and 81771196).

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Pharmacological inhibition of the NLRP3 inﬂammasome as a potential target for cancer-induced bone pain

Abstract

Graphical abstract

Introduction

Section snippets

Animals and ethics statement

MCC950, a selective NLRP3 inhibitor, relieved CIBP-induced mechanical allodynia

Discussion

Acknowledgements

Pharmacol. Res.

Exp. Neurol.

Free Radic. Biol. Med.

Phytomed.: Int. J. Phytother. Phytopharmacol.

J. Neuroinflammation

Immunity

Brain Behav. Immun.

Br. J. Anaesth.

Cancer Lett.

Cell

Int. Immunopharmacol.

Brain Behav. Immun.

Exp. Neurol.

J. Pain

Redox Biol.

Mol. Cell

Cell Rep.

Curr. Opin. Immunol.

Cellular and molecular mechanisms of calcium/calmodulin-dependent protein kinase II in chronic pain

J. Pharmacol. Exp. Ther.

Targeting glia for bone cancer pain

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PI3K/Akt pathway: a potential therapeutic target for chronic pain

Curr. Pharm. Des.

Resident macrophages initiating and driving inflammation in a monosodium urate monohydrate crystal-induced murine peritoneal model of acute gout

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Inhibition of peripheral macrophages by nicotinic acetylcholine receptor agonists suppresses spinal microglial activation and neuropathic pain in mice with peripheral nerve injury

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Caspase-1: is IL-1 just the tip of the ICEberg?

Cell Death Dis.

Molecular cloning of the interleukin-1 beta converting enzyme

Science