Proteomic and Metabolomic Responses to Anti-TNF and Anti-IL-6 Therapies in Rheumatoid Arthritis Patients
Overall, understanding the molecular changes associated with therapies for rheumatoid arthritis (RA) patients may help elucidate the pathogenesis of RA and potentially identify new therapeutic targets.
Therefore, in a new study, researchers set out to identify molecular patterns (proteins and endogenous metabolites) specified for three types of RA therapies: Inhibitors of IL6, TNF, and Janus kinases. Let's first take a brief look at the methods. Then we'll look at the results and learn what researchers are discussing and concluding.
Tumor necrosis factor (TNF) is a protein that is naturally produced by the body's immune system to fight off infections and diseases. It plays a key role in the body's inflammatory response, which helps to protect against harmful pathogens and injuries. However, when the body produces too much TNF, it can lead to chronic inflammation, which can damage healthy tissue and lead to a range of diseases, including rheumatoid arthritis, psoriasis, and inflammatory bowel disease.
How can the molecular profile of patients with rheumatoid arthritis (RA) be altered by therapeutic interventions, in particular by the use of inhibitors of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and Janus kinases (JAK)? These therapeutics can affect important cellular metabolic processes such as the tricarboxylic acid cycle, amino acid metabolism, and fatty acid metabolism. Studies have identified several metabolites and proteins associated with these therapies, including carbohydrates, amino acids, sugars, and fatty and carboxylic acids.
Effects of TNF inhibitors
TNF inhibitors have been shown to increase levels of histamine, glutamine, and phenylacetic acid and decrease levels of ethanolamine, hydroxyphenylpyruvic acid, and phosphocreatine. IL-6 inhibitors are associated with increased serum triglycerides, total cholesterol, and HDL-C levels, but also with an increase in LDL-C levels. JAK inhibitors have been shown to increase omega-3 fatty acid and docosahexaenoic acid (DHA) levels in treated patients, which is associated with significant pain relief.
Overall, understanding the molecular changes associated with these therapies may help elucidate the pathogenesis of RA and potentially identify new therapeutic targets.
Therefore, in a new study, researchers set out to identify molecular patterns (proteins and endogenous metabolites) specified for three types of RA therapies: Inhibitors of IL6, TNF, and Janus kinases.
Let's first take a brief look at the methods. Then we'll look at the results and learn what researchers are discussing and concluding.
Proteomics and Metabolomics
In the study, various reagents and chemicals such as urea, formic acid, trifluoroacetic acid, and tris(2-carboxyethyl)phosphine hydrochloride were used for proteomic analysis of samples obtained from patients with rheumatoid arthritis. The sample group consisted of 40 patients, and the samples were provided with information such as the unique identifier of the participant, type of drug therapy, anthropometric and clinical characteristics, assessment of disease activity, and clinical biochemical parameters of the blood. The preanalytical phase for proteomic analysis included various steps such as sample collection, processing, and storage.
Proteomic and Metabolomic Analysis Reveals Unique Response to Anti-TNF and Anti-IL6 Therapy in Patients with Rheumatoid Arthritis
The researchers analyzed plasma samples from three groups of RA patients who received two treatment options: One group got anti- TNF, the other anti-IL6. The proteome size before therapy was 884 proteins, while it was 554 and 763 proteins in the anti-αTNF and anti-IL6 groups, respectively. They found an astonishing number of proteins specific to each study group. They identified 677 proteins specific to the anti-αTNF group and 594 proteins specific to the anti-IL6 group. The researchers also identified 23 proteins common to all study groups. The most differentially expressed proteins were immunoglobulin A and G. Differences were also found in µ-chains specific for M-immunoglobulins.
Metabolomic analysis was less informative compared with the proteomic study, but still revealed interesting insights. The researchers focused on selected metabolites and analyzed the dynamics of changes in endogenous metabolites during 24 weeks of treatment. What did they find?
Patients with anti-TNF therapy showed a more than sixfold increase in 4-hydroxyproline (4-HP) compared with baseline, reflecting the intensification of collagen resorption by osteoclasts.
In contrast, patients on anti-IL6 therapy had at most a twofold increase in 4-HP. Similarly, 3-methylhistidine (3-MH) was an indicator of muscle tissue and extracellular matrix destruction.
In patients receiving anti-TNF therapy, 3-MH increased more than threefold and decreased twofold at week 24.
Arginine deficiency was observed in both groups before the start of therapy and was completely compensated after 24 weeks of treatment.
Immunochemical analysis for IL6 and αTNF confirmed the results of proteomic and metabolomic analyses. In the patients with anti-αTNF therapy, there was a decrease in TNF levels of twofold or more in 11 patients, whereas in the patients with anti-IL6 therapy, interleukin-6 levels decreased in 40% of cases at week 24 of treatment.
Comparing the Effects of Anti-TNF and Anti-IL-6 Therapies in Patients with Rheumatoid Arthritis
After presenting their findings, the researchers discuss the efficacy of anti-TNF and anti-IL6 therapies in RA patients. The study suggests that the presence of antibodies is a prerequisite for successful and effective therapy. This is particularly true of antibodies to citrullinated proteins (anti-CCP), anti-CarP, and anti-PAD4. Patients with predominant anti-αTNF therapy show the most marked improvement in terms of objective and basic clinical indicators, with superior levels of immunoglobulins A and G compared with patients with anti-IL6 therapy. How can this be explained? The observed changes are probably due to the formation of immune complexes of antibodies with the corresponding antigens.
The study also highlights the difference between the mechanisms of action of anti-TNF and anti-IL6 therapies and suggests that both cytokines (IL6 and TNF) are not only a consequence of the developing inflammatory response, but also a trigger for the formation of citrullinated proteins involved in the development of RA.
Findings and conclusions at a glance
In summary, the study found that both anti-TNF and anti-IL-6 therapies increased levels of immunoglobulins A and G, with anti-TNF therapy causing more severe changes. Arginine metabolism was also affected differently by the two groups, with anti-TNF therapy showing a more marked effect on the recovery of depleted arginine and the breakdown of citrulline. Bone tissue and collagen maintenance indicators behaved differently in the two groups, suggesting a different mechanism of matrix and bone tissue regulation.
Both therapies showed positive results in terms of disease severity, but the anti-IL-6 therapy showed faster dynamics of IL-6 reduction and improvement. Hemopexin was most likely to correlate with response and ESR, indicating its importance in monitoring the treatment efficacy of anti-IL6 therapy. The study suggests that anti-IL6 therapy may be more effective in patients with RA mediated by protein citrullination. In contrast, anti-TNF therapy may be better at normalizing arginine catabolism and citrulline conversion in patients with inflammatory arthropathies.