Mechanisms of Pain Hypersensitivity in a Human Skin Inflammation Model

Summary

The main goal of this double-blind, randomized, placebo-controlled crossover study is to understand the molecular mechanisms of inflammation-induced increased pain sensitivity (hyperalgesia). These mechanisms are studied using a recently established human model of skin inflammation that mimics aspects of skin infection. A localized inflammatory response in the skin of healthy volunteers is elicited by locally injecting a small, safe dose of Lipopolysaccharide (LPS), a major component of gram-negative bacteria.

The study addresses three key research questions:

* Role of RAGE: To investigate if certain inflammatory effects of LPS, which contribute to hyperalgesia, are mediated by a signaling pathway involving the RAGE receptor.
* Pain Sensitization: To examine how skin inflammation affects pain caused by acidic stimuli, and to differentiate this from purely mechanical pain.
* Role of TRPV1: To determine if the contribution of the TRPV1 ion channel to acid-induced pain is different in inflamed skin.

Participants will undergo an experimental session 4.5 hours after LPS injection to measure skin blood flow (using laser speckle imaging), mechanical pain sensitivity (using specialized tweezers), and pain induced by injecting a solution, of which the pH is gradually decreasing (acid-induced pain).

The study has minimal risks due to the small, safe doses of substances used ('microdosing') and aims to lay the groundwork for developing new treatments for inflammatory pain conditions.

Conditions

• Pain

Interventions

DRUG

Synthetic interstitial fluid (SIF) / SIF neutral pH

Intradermal injection of SIF at time point -4.5h, followed by laser speckle imaging, mechanical stimulation and intradermal injection of SIF with neutral pH (pH 7.4)

DRUG

Synthetic interstitial fluid (SIF) / SIF acidic pH

Intradermal injection of SIF at time point -4.5h, followed by laser speckle imaging, mechanical stimulation and intradermal injection of SIF with acidic pH (pH 7.4 to pH 5.7)

DRUG

Synthetic interstitial fluid (SIF) / SIF acidic pH + BCTC 1 µM

Intradermal injection of SIF at time point -4.5h, followed by laser speckle imaging, mechanical stimulation and intradermal injection of SIF with acidic pH (pH 7.4 to pH 5.7), containing BCTC 1 µM

DRUG

LPS 5 ng / SIF neutral pH

Intradermal injection of LPS 5 ng at time point -4.5h, followed by laser speckle imaging, mechanical stimulation and intradermal injection of SIF with neutral pH (pH 7.4)

DRUG

LPS 5 ng / SIF acidic pH

Intradermal injection of LPS 5 ng at time point -4.5h, followed by laser speckle imaging, mechanical stimulation and intradermal injection of SIF with acidic pH (pH 7.4 to pH 5.7)

DRUG

LPS 5 ng / SIF acidic pH + BCTC 1 µM

Intradermal injection of LPS 5 ng at time point -4.5h, followed by laser speckle imaging, mechanical stimulation and intradermal injection of SIF with acidic pH (pH 7.4 to pH 5.7), containing BCTC 1 µM

DRUG

LPS 5 ng + Azeliragon 100 µM / SIF neutral pH

Intradermal injection of LPS 5 ng + Azeliragon 100 µM at time point -4.5h, followed by laser speckle imaging, mechanical stimulation and intradermal injection of SIF with neutral pH (pH 7.4)

DRUG

LPS 5 ng + Azeliragon 100 µM / SIF acidic pH

Intradermal injection of LPS 5 ng + Azeliragon 100 µM at time point -4.5h, followed by laser speckle imaging, mechanical stimulation and intradermal injection of SIF with acidic pH (pH 7.4 to 5.7)

DRUG

LPS 5 ng + Resatorvid 10 µM / SIF neutral pH

Intradermal injection of LPS 5 ng + Resatorvid 10 µM at time point -4.5h, followed by laser speckle imaging, mechanical stimulation and intradermal injection of SIF with neutral pH (pH 7.4)

DRUG

LPS 5 ng + Resatorvid 10 µM / SIF acidic pH

Intradermal injection of LPS 5 ng + Resatorvid 10 µM at time point -4.5h, followed by laser speckle imaging, mechanical stimulation and intradermal injection of SIF with neutral pH (pH 7.4 to pH 5.7)

Sponsors & Collaborators

• Stefan Heber

  lead OTHER

Study Design

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

TRIPLE

Model

CROSSOVER

Eligibility

Min Age

18 Years

Max Age

70 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2025-06-17

Primary Completion

2025-07-11

Completion

2025-07-11

Countries

• Austria

Study Locations