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SomaScan P11K Proteomics Characterizes the Plasma Proteomic Profile of Exertional Heat Stroke and Highlights Innate Immune-Related Signaling Molecules

This study utilizes SomaScan P11K proteomics to characterize the plasma proteomic profile of exertional heat stroke, revealing significant innate immune and inflammation-related dysregulation with TLR2 identified as a key candidate biomarker for further mechanistic investigation.

Original authors: Jiamin Chen, Jinling Tan, Qi Liao, Chang Lu, Qiang Yan, Lingyu Huang, Yaoshuang Zou, Fengying Wang, Huaizhou Chen, Shenping Xie, Dong'e Tang, Baoyao Wang

Published 2026-09-23

📖 5 min read🧠 Deep dive

CC BY 4.0

Original authors: Jiamin Chen, Jinling Tan, Qi Liao, Chang Lu, Qiang Yan, Lingyu Huang, Yaoshuang Zou, Fengying Wang, Huaizhou Chen, Shenping Xie, Dong'e Tang, Baoyao Wang

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ⚕️ This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer

When the human body is pushed beyond its limits in extreme heat, it faces a crisis that goes far beyond simple overheating. Exertional heat stroke is a life-threatening emergency that occurs when intense physical activity meets high temperatures, causing the body's internal thermostat to fail. This failure triggers a chain reaction where the body's defense systems, designed to fight off infections and repair injuries, become overactive and turn against the very organs they are meant to protect. The result is a state of widespread inflammation that can damage the brain, heart, and kidneys. While doctors have long recognized the physical signs of this condition, the specific chemical messages circulating in the blood that drive this internal chaos have remained largely a mystery. Understanding these molecular signals is crucial because they could reveal new ways to diagnose the severity of the injury or identify targets for treatment.

A team of researchers set out to map these hidden chemical signals by looking directly at the proteins floating in the blood of people who had suffered from exertional heat stroke. Proteins are the workhorses of the body, acting as messengers, builders, and defenders. By using a highly sensitive scanning tool called SomaScan, which can detect thousands of different proteins at once, the scientists compared the blood samples of nine patients recovering from heat stroke against samples from ten healthy individuals. This approach allowed them to see the full landscape of the body's response, rather than just checking a few known markers. The scan revealed a dramatic shift in the blood's chemical composition: out of nearly eleven thousand proteins measured, one hundred and twenty had changed significantly. Seventy-one of these proteins had increased in number, while forty-nine had decreased, painting a picture of a body in a state of intense biological alert.

The researchers then asked what these changes meant for the body's overall function. By grouping the altered proteins into their known roles, a clear pattern emerged. The blood of the heat stroke patients was dominated by signals related to the innate immune system, which is the body's first line of defense against danger. The analysis highlighted pathways that the body uses to recognize tissue damage and trigger inflammation. Specifically, the data pointed to a group of molecules involved in recognizing danger signals and recruiting immune cells to the site of injury. Among the many proteins that changed, a few stood out as central hubs in this network of communication. The researchers identified Toll-like receptor 2, or TLR2, as the most connected protein in the network, followed closely by others like TLR7, CXCL10, ISG15, and IFIT3. These molecules are typically associated with how the body detects threats and launches an immune response, suggesting that the body treats the severe stress of heat stroke as a major biological emergency.

To ensure these findings were not just a fluke of the initial scan, the team took a second, independent step. They collected fresh blood samples from a new group of four heat stroke patients and three healthy people and measured the levels of TLR2 using a different, standard laboratory method. The results confirmed the initial discovery: the levels of TLR2 were significantly higher in the patients with heat stroke compared to the healthy individuals. This confirmation gave the researchers confidence that TLR2 is indeed a key player in the body's reaction to this type of injury. However, when they tested the other top candidates, CXCL10 and ISG15, in this smaller group, the results were less clear, showing no statistically significant difference. This suggests that while TLR2 is a robust marker, the other proteins may require larger studies to fully understand their role.

With TLR2 identified as a central figure in this response, the researchers looked for potential ways to influence it. They used a database that links proteins to known chemical compounds to see if any existing substances might interact with the proteins they had found. This search pointed to three specific compounds: Chlorophyllin, Prenylamine, and Inosinic acid. These chemicals were flagged as having a strong theoretical connection to the proteins involved in the heat stroke response. While the study did not test whether these compounds could treat heat stroke, their identification provides a starting point for future experiments. The researchers also noted that the body's reaction included signs of metabolic changes, such as shifts in how it processes fats, indicating that the injury affects more than just the immune system.

The study concludes that the blood of heat stroke patients carries a distinct signature of innate immune activation, with TLR2 emerging as a primary signal of this distress. The authors are careful to note that their work is an initial exploration. The group of patients they studied was small, and the blood was taken at a single moment in time, meaning they could not track how these protein levels changed as the patients recovered. Furthermore, while the data strongly suggests a link between heat stroke and these immune pathways, it does not yet prove that these molecules cause the damage or that blocking them would help. Nevertheless, this research provides a detailed map of the molecular landscape of heat stroke, moving the field from general observations of organ damage to a specific understanding of the immune signals involved. By highlighting TLR2 and related molecules, the study offers a new direction for scientists to investigate how the body reacts to extreme heat and how we might one day intervene to protect it.

Technical Summary: SomaScan P11K Proteomics Characterizes the Plasma Proteomic Profile of Exertional Heat Stroke

Problem Statement
Exertional heat stroke (EHS) is a life-threatening condition characterized by systemic inflammation and multi-organ injury, primarily affecting athletes, military personnel, and outdoor workers. While clinical manifestations and organ damage markers are well-documented, the underlying systemic molecular changes, particularly regarding circulating immune-related features, remain incompletely characterized. Existing studies have largely focused on routine biochemical parameters and specific inflammatory factors, which fail to capture the full scope of molecular alterations during acute heat injury. There is a need for a high-throughput approach to identify candidate molecules and biological pathways associated with EHS to facilitate deeper mechanistic understanding.

Methodology
This study employed a multi-stage analytical workflow combining high-throughput proteomics, bioinformatics, and targeted validation:

Study Cohorts: The study enrolled 9 patients with EHS and 10 healthy controls (HC) for the discovery phase. An independent cohort of 4 EHS patients and 3 HC was used for validation.
Proteomic Profiling: Plasma samples were analyzed using the SomaScan P11K platform, an aptamer-based targeted proteomics assay capable of detecting over 11,000 proteins. Samples were processed at three dilution factors (20%, 0.5%, 0.005%) to ensure coverage across abundance levels.
Differential Expression Analysis: Differentially expressed proteins (DEPs) were identified using significance criteria of $P < 0.05$ and $|Fold Change| \ge 1.5$ .
Bioinformatics and Network Analysis:
- Enrichment: Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed.
- Pathway Characterization: Hallmark pathway analysis was conducted using Gene Set Enrichment Analysis (GSEA) and single-sample GSEA (ssGSEA) to evaluate pathway-level alterations.
- Network Construction: A Protein-Protein Interaction (PPI) network was built using the STRING database and visualized via Cytoscape. Hub proteins were prioritized using the CytoHubba plugin (maximal clique centrality algorithm), and functional modules were identified using the MCODE plugin.
Target Validation: Selected candidate proteins were quantified in the independent cohort using Enzyme-Linked Immunosorbent Assay (ELISA).
Compound Screening: A DSigDB-based compound enrichment analysis was performed to identify small molecules associated with the candidate protein signatures.

Key Results

Proteomic Landscape: The SomaScan P11K platform detected 10,893 plasma proteins. The study identified 120 differentially expressed proteins (DEPs) between EHS patients and healthy controls, comprising 71 upregulated and 49 downregulated proteins.
Functional Enrichment:
- KEGG/GO: DEPs were significantly enriched in innate immunity and inflammation-related pathways. Specifically, the Toll-like receptor (TLR) signaling pathway and the RIG-I-like receptor signaling pathway were prominent.
- GO Categories: Enrichment was observed in biological processes such as defense response to virus, neutrophil activation, and immune response. Molecular functions included interleukin-18 binding and triacylated lipopeptide binding.
- Hallmark Pathways: ssGSEA and GSEA confirmed marked differences in innate immunity-related pathways, including interferon- $\alpha$ / $\gamma$ responses, TNF- $\alpha$ /NF- $\kappa$ B signaling, IL-6-JAK-STAT3 signaling, and complement activation.
Network Prioritization: PPI network analysis identified a cluster of hub proteins related to innate immunity. The top hub proteins included TLR2, TLR7, CXCL10, ISG15, and IFIT3. MCODE module analysis highlighted a specific TLR/interferon-related module consisting of these five proteins.
Experimental Validation: In the independent validation cohort, TLR2 levels were significantly elevated in EHS patients compared to controls ( $P = 0.0061$ ), consistent with the proteomic findings. However, CXCL10 and ISG15 did not show statistically significant differences in the ELISA validation ( $P > 0.05$ ).
Compound Association: DSigDB analysis linked the candidate protein set to several compounds, with Chlorophyllin, Prenylamine, and Inosinic acid ranking highest. Notably, Inosinic acid was associated with TLR2, TLR7, and CXCL10.

Key Contributions

Resource Generation: The study provides the first exploratory plasma proteomic resource for EHS using the SomaScan P11K platform, detailing the expression profiles of over 10,000 proteins.
Identification of Innate Immunity Signatures: The work systematically highlights that innate immune recognition and inflammatory responses are prominent biological features of EHS, moving beyond routine clinical markers.
Prioritization of TLR2: Through a combination of network topology and experimental validation, the study prioritizes TLR2 as a key molecular feature associated with EHS, suggesting its role in recognizing tissue injury-related danger signals.
Therapeutic Leads: The study identifies candidate compounds (e.g., Chlorophyllin, Prenylamine, Inosinic acid) that may interact with the identified immune-related protein signatures, offering potential directions for future mechanistic investigation.

Significance and Claims
The authors position this work as an exploratory study that establishes a foundational plasma proteomic profile for EHS. The significance lies in the identification of innate immune-related signaling molecules, particularly TLR2, as potential targets for further validation and mechanistic investigation.

The paper explicitly notes that while the findings suggest a link between EHS and innate immune activation (potentially triggered by endogenous damage-associated molecules like HMGB1 or nucleic acids released during heat stress), the study does not claim to have established direct causal regulatory relationships. The authors emphasize that the enrichment of viral infection-related pathways reflects shared molecular components of nucleic acid recognition rather than evidence of actual viral infection in EHS patients.

The study concludes that these findings provide a "candidate biological framework" and a prioritized list of molecules and compounds for future research, acknowledging limitations such as the small sample size, cross-sectional design, and the need for larger independent cohorts and multi-omics integration to fully validate the biological significance of these candidates.

Technical Summary: SomaScan P11K Proteomics Characterizes the Plasma Proteomic Profile of Exertional Heat Stroke

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