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Prostaglandin metabolite induces inhibition of TRPA1 and channel-dependent nociception.

Weng Y, Batista-Schepman PA, Barabas ME, Harris EQ, Dinsmore TB, Kossyreva EA, Foshage AM, Wang MH, Schwab MJ, Wang VM, Stucky CL, Story GM - Mol Pain (2012)

Bottom Line: Ca2+ imaging studies of DRG neurons demonstrated that 15d-PGJ2 pre-exposure reduced the magnitude and number of neuronal responses to AITC, but not CAP.AITC responses were not reduced when neurons were pre-exposed to 15d-PGJ2 combined with HC-030031 (TRPA1 antagonist), demonstrating that inhibitory effects of 15d-PGJ2 depend on TRPA1 activation.Collectively, our studies support that TRPA1 agonists may be useful as pain therapeutics.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Anesthesiology, Washington University Pain Center, St. Louis, MO 63110, USA.

ABSTRACT

Background: The Transient Receptor Potential (TRP) ion channel TRPA1 is a key player in pain pathways. Irritant chemicals activate ion channel TRPA1 via covalent modification of N-terminal cysteines. We and others have shown that 15-Deoxy-Δ12, 14-prostaglandin J2 (15d-PGJ2) similarly activates TRPA1 and causes channel-dependent nociception. Paradoxically, 15d-PGJ2 can also be anti-nociceptive in several pain models. Here we hypothesized that activation and subsequent desensitization of TRPA1 in dorsal root ganglion (DRG) neurons underlies the anti-nociceptive property of 15d-PGJ2. To investigate this, we utilized a battery of behavioral assays and intracellular Ca2+ imaging in DRG neurons to test if pre-treatment with 15d-PGJ2 inhibited TRPA1 to subsequent stimulation.

Results: Intraplantar pre-injection of 15d-PGJ2, in contrast to mustard oil (AITC), attenuated acute nocifensive responses to subsequent injections of 15d-PGJ2 and AITC, but not capsaicin (CAP). Intraplantar 15d-PGJ2-administered after the induction of inflammation-reduced mechanical hypersensitivity in the Complete Freund's Adjuvant (CFA) model for up to 2 h post-injection. The 15d-PGJ2-mediated reduction in mechanical hypersensitivity is dependent on TRPA1, as this effect was absent in TRPA1 knockout mice. Ca2+ imaging studies of DRG neurons demonstrated that 15d-PGJ2 pre-exposure reduced the magnitude and number of neuronal responses to AITC, but not CAP. AITC responses were not reduced when neurons were pre-exposed to 15d-PGJ2 combined with HC-030031 (TRPA1 antagonist), demonstrating that inhibitory effects of 15d-PGJ2 depend on TRPA1 activation. Single daily doses of 15d-PGJ2, administered during the course of 4 days in the CFA model, effectively reversed mechanical hypersensitivity without apparent tolerance or toxicity.

Conclusions: Taken together, our data support the hypothesis that 15d-PGJ2 induces activation followed by persistent inhibition of TRPA1 channels in DRG sensory neurons in vitro and in vivo. Moreover, we demonstrate novel evidence that 15d-PGJ2 is analgesic in mouse models of pain via a TRPA1-dependent mechanism. Collectively, our studies support that TRPA1 agonists may be useful as pain therapeutics.

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Effect of 15d-PGJ2 on mechanical- and heat-sensitivity. (A) 15 mM 15d-PGJ2 (ipl.) attenuates CFA-induced mechanical hypersensitivity. Von Frey measurements were recorded before CFA injection (Naïve), 24 h post-CFA injection and at noted time points. 15d-PGJ2 was administered 1 h prior to von Frey measurements. (B) 15d-PGJ2 shows no analgesic effect (no change latency to licking or flicking) against inflammatory heat hypersensitivity in Hargreaves test. (C) 15d-PGJ2 itself does not cause mechanical hypersensitivity (1 h after ipl. injection), while AITC does (*p < 0.05, **p < 0.01, *** p < 0.001; n = 8 per group; values expressed as mean ± SEM). Data were analyzed using RMANOVA with Bonferonni post-hoc comparisons (A) or two-tailed Student’s t-test (B and C).
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Figure 1: Effect of 15d-PGJ2 on mechanical- and heat-sensitivity. (A) 15 mM 15d-PGJ2 (ipl.) attenuates CFA-induced mechanical hypersensitivity. Von Frey measurements were recorded before CFA injection (Naïve), 24 h post-CFA injection and at noted time points. 15d-PGJ2 was administered 1 h prior to von Frey measurements. (B) 15d-PGJ2 shows no analgesic effect (no change latency to licking or flicking) against inflammatory heat hypersensitivity in Hargreaves test. (C) 15d-PGJ2 itself does not cause mechanical hypersensitivity (1 h after ipl. injection), while AITC does (*p < 0.05, **p < 0.01, *** p < 0.001; n = 8 per group; values expressed as mean ± SEM). Data were analyzed using RMANOVA with Bonferonni post-hoc comparisons (A) or two-tailed Student’s t-test (B and C).

Mentions: In separate groups of mice, we measured mechanical thresholds using the up and down method at baseline and 24 h post-CFA injection (day 1, Figure 1A). One day after CFA injection, we injected 1.5 or 15 mM 15d-PGJ2 (10 μL) into the plantar hindpaw 1 h prior to von Frey measurements. As shown in Figure 1A, 15 mM 15d-PGJ2 induced a marked reversal of mechanical hypersensitivity relative to vehicle (and 1.5 mM 15d-PGJ2). The effect was maximal at 2 h post injection. In contrast, 15d-PGJ2 had no effect on heat hypersensitivity as measured with the Hargreaves assay, suggesting that the effect of 15d-PGJ2 is modality specific (Figure 1B). Administering 15d-PGJ2 prior to the induction of inflammation by CFA had no effect on mechanical thresholds in CFA- or vehicle-injected mice (data not shown, see also below).


Prostaglandin metabolite induces inhibition of TRPA1 and channel-dependent nociception.

Weng Y, Batista-Schepman PA, Barabas ME, Harris EQ, Dinsmore TB, Kossyreva EA, Foshage AM, Wang MH, Schwab MJ, Wang VM, Stucky CL, Story GM - Mol Pain (2012)

Effect of 15d-PGJ2 on mechanical- and heat-sensitivity. (A) 15 mM 15d-PGJ2 (ipl.) attenuates CFA-induced mechanical hypersensitivity. Von Frey measurements were recorded before CFA injection (Naïve), 24 h post-CFA injection and at noted time points. 15d-PGJ2 was administered 1 h prior to von Frey measurements. (B) 15d-PGJ2 shows no analgesic effect (no change latency to licking or flicking) against inflammatory heat hypersensitivity in Hargreaves test. (C) 15d-PGJ2 itself does not cause mechanical hypersensitivity (1 h after ipl. injection), while AITC does (*p < 0.05, **p < 0.01, *** p < 0.001; n = 8 per group; values expressed as mean ± SEM). Data were analyzed using RMANOVA with Bonferonni post-hoc comparisons (A) or two-tailed Student’s t-test (B and C).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3526547&req=5

Figure 1: Effect of 15d-PGJ2 on mechanical- and heat-sensitivity. (A) 15 mM 15d-PGJ2 (ipl.) attenuates CFA-induced mechanical hypersensitivity. Von Frey measurements were recorded before CFA injection (Naïve), 24 h post-CFA injection and at noted time points. 15d-PGJ2 was administered 1 h prior to von Frey measurements. (B) 15d-PGJ2 shows no analgesic effect (no change latency to licking or flicking) against inflammatory heat hypersensitivity in Hargreaves test. (C) 15d-PGJ2 itself does not cause mechanical hypersensitivity (1 h after ipl. injection), while AITC does (*p < 0.05, **p < 0.01, *** p < 0.001; n = 8 per group; values expressed as mean ± SEM). Data were analyzed using RMANOVA with Bonferonni post-hoc comparisons (A) or two-tailed Student’s t-test (B and C).
Mentions: In separate groups of mice, we measured mechanical thresholds using the up and down method at baseline and 24 h post-CFA injection (day 1, Figure 1A). One day after CFA injection, we injected 1.5 or 15 mM 15d-PGJ2 (10 μL) into the plantar hindpaw 1 h prior to von Frey measurements. As shown in Figure 1A, 15 mM 15d-PGJ2 induced a marked reversal of mechanical hypersensitivity relative to vehicle (and 1.5 mM 15d-PGJ2). The effect was maximal at 2 h post injection. In contrast, 15d-PGJ2 had no effect on heat hypersensitivity as measured with the Hargreaves assay, suggesting that the effect of 15d-PGJ2 is modality specific (Figure 1B). Administering 15d-PGJ2 prior to the induction of inflammation by CFA had no effect on mechanical thresholds in CFA- or vehicle-injected mice (data not shown, see also below).

Bottom Line: Ca2+ imaging studies of DRG neurons demonstrated that 15d-PGJ2 pre-exposure reduced the magnitude and number of neuronal responses to AITC, but not CAP.AITC responses were not reduced when neurons were pre-exposed to 15d-PGJ2 combined with HC-030031 (TRPA1 antagonist), demonstrating that inhibitory effects of 15d-PGJ2 depend on TRPA1 activation.Collectively, our studies support that TRPA1 agonists may be useful as pain therapeutics.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Anesthesiology, Washington University Pain Center, St. Louis, MO 63110, USA.

ABSTRACT

Background: The Transient Receptor Potential (TRP) ion channel TRPA1 is a key player in pain pathways. Irritant chemicals activate ion channel TRPA1 via covalent modification of N-terminal cysteines. We and others have shown that 15-Deoxy-Δ12, 14-prostaglandin J2 (15d-PGJ2) similarly activates TRPA1 and causes channel-dependent nociception. Paradoxically, 15d-PGJ2 can also be anti-nociceptive in several pain models. Here we hypothesized that activation and subsequent desensitization of TRPA1 in dorsal root ganglion (DRG) neurons underlies the anti-nociceptive property of 15d-PGJ2. To investigate this, we utilized a battery of behavioral assays and intracellular Ca2+ imaging in DRG neurons to test if pre-treatment with 15d-PGJ2 inhibited TRPA1 to subsequent stimulation.

Results: Intraplantar pre-injection of 15d-PGJ2, in contrast to mustard oil (AITC), attenuated acute nocifensive responses to subsequent injections of 15d-PGJ2 and AITC, but not capsaicin (CAP). Intraplantar 15d-PGJ2-administered after the induction of inflammation-reduced mechanical hypersensitivity in the Complete Freund's Adjuvant (CFA) model for up to 2 h post-injection. The 15d-PGJ2-mediated reduction in mechanical hypersensitivity is dependent on TRPA1, as this effect was absent in TRPA1 knockout mice. Ca2+ imaging studies of DRG neurons demonstrated that 15d-PGJ2 pre-exposure reduced the magnitude and number of neuronal responses to AITC, but not CAP. AITC responses were not reduced when neurons were pre-exposed to 15d-PGJ2 combined with HC-030031 (TRPA1 antagonist), demonstrating that inhibitory effects of 15d-PGJ2 depend on TRPA1 activation. Single daily doses of 15d-PGJ2, administered during the course of 4 days in the CFA model, effectively reversed mechanical hypersensitivity without apparent tolerance or toxicity.

Conclusions: Taken together, our data support the hypothesis that 15d-PGJ2 induces activation followed by persistent inhibition of TRPA1 channels in DRG sensory neurons in vitro and in vivo. Moreover, we demonstrate novel evidence that 15d-PGJ2 is analgesic in mouse models of pain via a TRPA1-dependent mechanism. Collectively, our studies support that TRPA1 agonists may be useful as pain therapeutics.

Show MeSH
Related in: MedlinePlus