Burn injuries often incite substantial morbidity and lethality aftermath. Severe burn injuries due to hot liquids or solids and fire induce pathophysiological and inflammatory responses, metabolic alterations, and distributive shock in distant deeper organs that can extensively persist up to several years after the initial burn insult and are extremely unmanageable, leading towards multi-organ damage. Comprehending how different organs get triggered in response to burn injuries will help to develop organ-specific remedies. Scientists from the University of Colorado, USA, examined burn injuries’ effects on the liver and found crucial significance in this aspect.
Insights into Previous Key Findings
The liver is one of the essential organs that can suffer consequential molecular and histological alterations followed by cutaneous burns, such as hepatomegaly, fatty filtration, edema, oxidative stress, hepatic damage, and cell death. The burn-inflicted liver can elicit maladjusted metabolic and immune responses in patients, as the liver plays a significant role in the body’s metabolic processes. Elevated levels of hepatic enzymes like aminotransferases were observed in blood serum during the first week, post-burn. The researchers found that elevated transaminases remarkably lower the survival rate in burn patients.
Moreover, the dysregulations are noticed to be aggravated in aged animal models, demonstrating the greater vulnerability of the organ towards burn-induced deterioration. Thus, comprehensive age-specific genetics and metabolic studies are fundamental to identifying critical elements for designing effective drug targets and remediation. Transcriptomics and metabolic analysis of the liver in young and Aged mouse models, followed by predicting possible drug drugs to regulate the dysfunctions analyzed in the study, reveals various important fundamental aspects that can assist in clinical treatment and burn injury management.
An Overview of the Experimental Procedure
The researchers divided young 3–4 month old (equivalent to 65–70 human years) and aged 20–22 month old (equivalent to 20–25 human years) BALB/c mice into four experimental groups: young sham, young burn, aged sham, and aged burn, and to induce burn injury, they followed the protocol defined by Faunce et al.
- For transcriptomics analysis, RNA was extracted from the hepatic lobe of four groups of mice to perform gene expression analysis using RT-PCR and RNA sequencing. The transcriptome represents all the transcribed genes in a cell, and gene expression profiles can be analyzed from this data to mark the key genes differentially expressed due to burn injury.
- The researchers performed the metabolomic analysis with Mass Spectrometric (MS) approaches. Mechanisms that create the phenotypic expression are inferred from Metabolomic analysis.
- Besides, the scientist proposed drugs that can be repurposed to cure hepatic malfunctions.
Unraveling Age-Related Liver Dysfunction in Burn Victims
The analysis of the Transcriptome and Metabolomic profiles led to the discovery following facets:
- Hepatic Transcriptome Analysis of Sham Mice Group
Seventy-five genes were upregulated in aged sham mice compared to the young sham group. Among those, 13 genes were associated with immunoglobulin (antibody) production. The genes up-regulated in aged mice were associated with two pathways, “PPAR signaling” and “IL-17 signaling”. These results correlated with the common age-related amendment to the characteristic chronic inflammatory state of aged people known as inflammaging.
- Hepatic Transcriptome Analysis of Burn injured Mice Group
Transcriptome profile of the liver of both the aged and young mice displayed overexpression of 157 genes. Among these, eight genes are intricately associated with protein export, while a notable thirty genes are intimately involved in protein processing within the endoplasmic reticulum. Additionally, a handful of five genes have been identified concerning fructose and mannose metabolism, alongside six genes playing a pivotal role in IL-17 signaling. One hundred fourteen genes are observed downregulated across all the burn-injured mice.
In Aged burn-injured mice, 46 up-regulated, and 89 downregulated genes were identified in hepatic transcriptome compared to the young group. The downregulated genes were linked with arginine biosynthesis, bile secretion, steroid hormone synthesis, chemical carcinogenesis, metabolism of linoleic acid, arachidonic acid, and retinol and xenobiotics metabolism by cytochrome P450. Time course investigation validated that the downregulation of multiple cytochrome P450 genes progressively becomes severe.
Liver physiology dramatically shifts towards synthesizing proteins essential to the defense against burn injury and reduces the production of constitutional proteins, steroid hormones, bile, and numerous cytochrome p450 metabolic processes, etc. However, prolonged hyperfunction of the liver is detrimental to burn victims. For instance, Cytochrome P450 genes are directly affiliated with many metabolic pathways. Persistent downregulation of the P450 enzyme yield oxidative stress, DNA repair, toxin accumulation, and so on, leading toward Multiple Organ Dysfunction Syndrome (MDOS).
- Metabolomic Analysis Inferences
Metabolomic profiling of liver samples indicated that mice, irrespective of age, have reduced amino acid levels in response to burn injury. Integrating dysregulated metabolite with differentially expressed genes via the Ingenuity Pathway Analysis tool elucidated the roles of Egfr receptors in metabolic disturbances. Pronounced downregulation of phenylalanine and methionine levels and higher upregulation of UMP levels were found in aged mice. Severe downregulation of the metabolic process like glutathione metabolism and citrate cycle (TCA cycle) in the aged animal group was marked.
Targeted Drug Interventions
Utilizing the Connectivity map tool – Cmap, the scientists searched for drugs that could potentially exaggerate or counteract the molecular perturbances.
- Commonly used drugs like albendazole, dextromethorphan, and valsartan can cause similar effects as commonly observed dysregulated genes in the hepatic samples. Widely used drugs like enalapril, atorvastatin, and cilostazol could cause the opposite transcriptional effect in mice’s liver after burn injury.
- Etomidate, probenecid, flumetazone, and nadolol arouse similar transcriptional changes observed differentially in aged mice. Melperone, clozapine, dexamethasone, and sertraline are predicted to cause opposite transcriptional changes in those aged mice group.
The key molecular-level observation can serve as efficacious drug targets. Further in vivo studies and trials are necessary to medicate the predicted drugs. As the scientists themselves acknowledge the curbs of the experiments, such as the experimental condition don’t exactly replicate the clinical conditions, burn patients are treated in different environmental conditions (ICU) unlike mice were treated, the disparity in cutaneous physiology between rodents and humans, and differential immunological responses may arise. Nonetheless, the study is another significant step toward burn trauma care if the research is further accentuated.
Article Source: Reference Paper
Aditi is a consulting scientific writing intern at CBIRT, specializing in explaining interdisciplinary and intricate topics. As a student pursuing an Integrated PG in Biotechnology, she is driven by a deep passion for experiencing multidisciplinary research fields. Aditi is particularly fond of the dynamism, potential, and integrative facets of her major. Through her articles, she aspires to decipher and articulate current studies and innovations in the Bioinformatics domain, aiming to captivate the minds and hearts of readers with her insightful perspectives.