Mouse study links spinal Hsp90 inhibition to enhanced morphine pain relief through DUSP15 in CGRP neurons

In a mouse study, inhibiting heat shock protein 90 (Hsp90) in the spinal cord increased the pain-relieving effect of morphine by upregulating dual specificity protein phosphatase 15 (DUSP15), at least partly in calcitonin gene-related peptide (CGRP) neurons. Knockdown experiments showed that DUSP15 was required for the enhanced antinociception produced by spinal Hsp90 inhibition.

The researchers used male and female CD-1 mice in approximately equal numbers across experiments. They administered the non-isoform-selective Hsp90 inhibitor 17-AAG intrathecally and measured pain responses with a warm-water tail-flick assay and a post-surgical paw-incision model that assessed mechanical sensitivity through von Frey testing. Systemic morphine was used to evaluate antinociception. Investigators were blinded to treatment groups, and no significant sex differences were detected.

Spinal Hsp90 inhibition with 17-AAG approximately doubled morphine’s antinociceptive efficacy in both the tail-flick and paw-incision models. In vivo CRISPR knockdown of DUSP15 reversed this enhancement to baseline levels, while DUSP15 knockdown alone did not change morphine’s effect in the absence of 17-AAG. Immunohistochemistry also showed increased DUSP15 expression in the dorsal horn after Hsp90 inhibition.

A separate DUSP15 small interfering RNA approach reproduced the behavioral result in the tail-flick model, reducing the enhanced morphine effect caused by 17-AAG without independently altering morphine antinociception. The researchers therefore supported the necessity of DUSP15 using two complementary gene-silencing methods, although the work did not test whether DUSP15 is sufficient by itself to enhance opioid responses.

Biochemical and behavioral experiments placed DUSP15 upstream of phosphorylated ERK MAPK and phosphorylated AMPK in the spinal Hsp90–opioid receptor signaling cascade. DUSP15 knockdown eliminated enhanced ERK staining after Hsp90 inhibition and opioid stimulation. It also prevented the reduction in AMPK phosphorylation normally produced by 17-AAG. Blocking AMPK with dorsomorphin restored the enhanced morphine antinociception lost after DUSP15 knockdown in both pain models.

Immunohistochemical staining showed that Hsp90 inhibition increased the overlap of DUSP15 and CGRP signals in the superficial spinal dorsal horn. More selective CRISPR editing directed at DUSP15 in CGRP-expressing neurons removed that overlap and reversed the 17-AAG-associated enhancement of morphine antinociception in the tail-flick assay. These findings identify CGRP neurons as one necessary site of DUSP15 action in the mouse spinal cord.

The authors proposed a model in which DUSP15 reduces AMPK phosphorylation, relieving an inhibitory feedback pathway on ERK signaling and thereby strengthening opioid antinociception. However, the experiments did not demonstrate that DUSP15 directly dephosphorylates AMPK, and an intermediate factor could be involved. The cellular and spatial links between AMPK and ERK also remain unresolved.

This was a preclinical mouse study, not evidence of clinical benefit in people. Most experiments used the non-isoform-selective inhibitor 17-AAG, so the specific Hsp90 isoforms involved were not distinguished. DUSP15 was not evaluated in the authors’ chronic HIV-induced peripheral neuropathy model, and possible sex-dependent effects or distinct CGRP subpopulations were not defined.

Subject of Research: Mechanistic mouse study of spinal Hsp90 inhibition, DUSP15 and enhanced opioid antinociception

Article Title: Inhibition of heat shock protein 90 in the mouse spinal cord enhances opioid antinociception via the upregulation of dual specificity protein phosphatase 15 (DUSP15) in CGRP neurons

Article References: Gabriel, K. A., Bowden, J. L., & Streicher, J. M. (2026). Inhibition of heat shock protein 90 in the mouse spinal cord enhances opioid antinociception via the upregulation of dual specificity protein phosphatase 15 (DUSP15) in CGRP neurons. Frontiers in Pharmacology, 17, Article 1734504. https://doi.org/10.3389/fphar.2026.1734504

Image Credits: AI Generated

DOI: 10.3389/fphar.2026.1734504

Keywords: Hsp90 inhibition, DUSP15, CGRP neurons, opioid antinociception, morphine, mouse spinal cord, ERK MAPK, AMPK, CRISPR, pain models, Inhibition, heat