TRPV1 Antagonists Elevate Cell Surface Populations of Receptor Protein and Exacerbate TRPV1-Mediated Toxicities in Human Lung Epithelial Cells

Abstract

TRPV1 mediates cell death and pro-inflammatory cytokine production in lung epithelial cells exposed to prototypical receptor agonists. This study shows that NHBE, BEAS-2B and TRPV1 over-expressing BEAS-2B cells pre-treated with various TRPV1 antagonists become sensitized to the prototypical TRPV1 agonist, nonivamide, via a mechanism that involves translocation of existing receptor from the endoplasmic reticulum to the plasma membrane. As such, typical cellular responses to agonist treatment, as measured by calcium flux, inflammatory cytokine gene induction, and cytotoxicity were exacerbated. These data were in contrast to the results obtained when TRPV1 antagonists were co-administered with nonivamide; conditions which inhibited TRPV1-mediated effects. The antagonists LJO-328, SC0030, and capsazepine increased the cytotoxicity of nonivamide by approximately 20-fold and agonist-induced calcium flux by approximately 6-fold. Inflammatory-cytokine gene induction by nonivamide was also increased significantly by pre-treatment with the antagonists. The enhanced responses were inhibited by the co-administration of antagonists with nonivamide, confirming that increases in sensitivity were attributable to increased TRPV1-associated activity. Sensitization was attenuated by brefeldin A (a golgi transport inhibitor), but not cycloheximide (a protein synthesis inhibitor), or actinomycin D (a transcription inhibitor). Sensitized cells exhibited increased calcium flux from extracellular calcium sources, while unsensitized cells exhibited calcium flux originating primarily from intracellular stores. These results demonstrate the presence of a novel mechanism for regulating the sub-cellular distribution of TRPV1 and subsequent control of cellular sensitivity to TRPV1 agonists.

Effects of cell type and culture media on Interleukin-6 secretion in response to environmental particles

“…Recently our research group showed that both cytotoxicity and induction of IL-6 in response to the TRPV-1 receptor agonist nonivamide was modulated by short-term drug pretreatments through a mechanism involving translocation of receptors from the endoplasmic reticulum to cell surface (Johansen, Reilly et al 2006). Alternatively, the cell response could depend on the availability of receptor cofactors.…”

Structure-Activity Relationship of Capsaicin Analogs and Transient Receptor Potential Vanilloid 1-Mediated Human Lung Epithelial Cell Toxicity

“…In cultured human lung cells, capsaicin and other TRPV1 agonists activated TRPV1 and promoted both time-and dose-dependent cytokine release, ER stress, and cell death (Reilly et al, 2003b(Reilly et al, , 2005Thomas et al, 2007). Increased expression of interleukin-6 and interleukin-8 were associated with activation of cell surface TRPV1, and these molecules contribute to pulmonary inflammation and neutrophilia in the lung (Reilly et al, 2005;Johansen et al, 2006;Thomas et al, 2007). Activation of ER-associated/ intracellular TRPV1 causes ER stress, activation of eukaryotic translation initiation factor 2␣ kinase, induction of GADD153 mRNA and protein, and cell death (Reilly et al, 2003b(Reilly et al, , 2005Johansen et al, 2006;Thomas et al, 2007).…”

“…Increased expression of interleukin-6 and interleukin-8 were associated with activation of cell surface TRPV1, and these molecules contribute to pulmonary inflammation and neutrophilia in the lung (Reilly et al, 2005;Johansen et al, 2006;Thomas et al, 2007). Activation of ER-associated/ intracellular TRPV1 causes ER stress, activation of eukaryotic translation initiation factor 2␣ kinase, induction of GADD153 mRNA and protein, and cell death (Reilly et al, 2003b(Reilly et al, , 2005Johansen et al, 2006;Thomas et al, 2007). This latter process is proposed to be the mechanism by which capsaicin damages epithelial cells in the respiratory tract.…”

The Transient Receptor Potential Vanilloid-1 Channel in Thermoregulation: A Thermosensor It Is Not

“…A recent study in rats with Abbott Laboratories' drug ABT-102 (Honore et al, 2009) also has shown that repeated dosing can favorably shift the ratio of the desired effect (analgesia) to the unwanted side effect (hyperthermia). The selective restoration of some TRPV1-mediated functions after the administration of a TRPV1 antagonist can be due to the antagonist-sensitive regulation of the subcellular distribution of TRPV1; via such a mechanism, TRPV1 antagonists can increase the cell surface expression of the TRPV1 protein and, subsequently, the cellular sensitivity to TRPV1 agonists (Johansen et al, 2006). However, when AMG 517 was administered in humans in Amgen's trials, the results seemed less promising: of the three doses tested, only the highest dose (10 mg) caused a hyperthermic response that attenuated with repeated dosing (Fig.…”