1-Methyl tryptophan, an indoleamine 2,3-dioxygenase inhibitor, attenuates cardiac and hepatic dysfunction in rats with biliary cirrhosis

Kynurenines as a Novel Target for the Treatment of Inflammatory Disorders

This review discusses the potential of targeting the kynurenine pathway (KP) in the treatment of inflammatory diseases. The KP, responsible for the catabolism of the amino acid tryptophan (TRP), produces metabolites that regulate various physiological processes, including inflammation, cell cycle, and neurotransmission. These metabolites, although necessary to maintain immune balance, may accumulate excessively during inflammation, leading to systemic disorders. Key KP enzymes such as indoleamine 2,3-dioxygenase 1 (IDO1), indoleamine 2,3-dioxygenase 2 (IDO2), tryptophan 2,3-dioxygenase (TDO), and kynurenine 3-monooxygenase (KMO) have been considered promising therapeutic targets. It was highlighted that both inhibition and activation of these enzymes may be beneficial, depending on the specific inflammatory disorder. Several inflammatory conditions, including autoimmune diseases, for which modulation of KP activity holds therapeutic promise, have been described in detail. Preclinical studies suggest that this modulation may be an effective treatment strategy for diseases for which treatment options are currently limited. Taken together, this review highlights the importance of further research on the clinical application of KP enzyme modulation in the development of new therapeutic strategies for inflammatory diseases.

Cardiac complications caused by biliary diseases: A review of clinical manifestations, pathogenesis and treatment strategies of cholecardia syndrome

Gallbladder and biliary diseases (GBDs) are one of the most common digestive diseases. The connections between GBDs and several organs other than the liver have gradually surfaced accompanied by the changes in people's diet structure and the continuous improvement of medical diagnosis technology. Among them, cholecardia syndrome that takes the heart as the important target of GBDs complications has been paid close attention. However, there are still no systematic report about its corresponding clinical manifestations and pathogenesis. This review summarized recent reported types of cholecardia syndrome and found that arrhythmia, myocardial injury, acute coronary syndrome and heart failure are common in the general population. Besides, the clinical diagnosis rate of intrahepatic cholestasis of pregnancy (ICP) and Alagille syndrome associated with gene mutation is also increasing. Accordingly, the underlying pathogenesis including abnormal secretion of bile acid, gene mutation, translocation and deletion (JAG1, NOTCH2, ABCG5/8 and CYP7A1), nerve reflex and autonomic neuropathy were further revealed. Finally, the potential treatment measures and clinical medication represented by ursodeoxycholic acid were summarized to provide assistance for clinical diagnosis and treatment.

IDO/Kynurenine; novel insight for treatment of inflammatory diseases

Inflammation and oxidative stress play pivotal roles in pathogenesis of many diseases including cancer, type 2 diabetes, cardiovascular disease, atherosclerosis, neurological diseases, and inflammatory diseases such as inflammatory bowel disease (IBD). Inflammatory mediators such as interleukins (ILs), interferons (INF-s), and tumor necrosis factor (TNF)-α are related to an extended chance of inflammatory diseases initiation or progression due to the over expression of the nuclear factor Kappa B (NF-κB), signal transducer of activators of transcription (STAT), nod-like receptor family protein 3 (NLRP), toll-like receptors (TLR), mitogen-activated protein kinase (MAPK), and mammalian target of rapamycin (mTOR) pathways. These pathways are completely interconnected. Theindoleamine 2,3 dioxygenase (IDO) subset of the kynurenine (KYN) (IDO/KYN), is a metabolic inflammatory pathway involved in production of nicotinamide adenine dinucleotide (NAD + ). It has been shown that IDO/KYN actively participates in inflammatory processes and can increase the secretion of cytokines that provoke inflammatory diseases. Data were extracted from clinical and animal studies published in English between 1990-April 2022, which were collected from PubMed, Google Scholar, Scopus, and Cochrane library. IDO/KYN is completely associated with inflammatory-related pathways, thus leading to the production of cytokines such as TNF-α, IL-1β, and IL-6, and ultimately development and progression of various inflammatory disorders. Inhibition of the IDO/KYN pathway might be a novel therapeutic option for inflammatory diseases. Herein, we gathered data on probable interactions of the IDO/KYN pathway with induction of some inflammatory diseases.

Therapeutic potential of bromhexine for acute itch in mice: Involvement of TMPRSS2 and kynurenine pathway

Itching is an unpleasant sensation on the skin that could negatively impact the quality of life. Over the years, many non-pharmacological and pharmacological approaches have been introduced to mitigate this burdensome condition; However, the effectiveness of these methods remains questioned. Bromhexine, derived from the Adhatoda vasica plant, is a safe drug with minimal side effects. It has been widely used in managing respiratory symptoms over the years. The results of our study revealed that bromhexine has the potential to alleviate acute itch induced by Compound 48/80, a known mast cell destabilizer. According to our findings, bromhexine exerts its antipruritic effects primarily by inhibiting the Transmembrane Protein Serine Protease 2 (TMPRSS2) and, to a lesser extent, by decreasing the activation of the Kynurenine Pathway (KP). We further investigated the KP involvement by administrating 1-Methyl Tryptophan (1-MT), a known indoleamine-2,3-dioxygenase (IDO) inhibitor. 1-MT was found to be effective in reducing the itch itself. Moreover, co-administration of bromhexine and 1-MT resulted in synergistic antipruritic effects, suggesting that KP plays a role in acute itch. To conclude, we have presented for the first time a repositioning of bromhexine as a treatment for acute itch. In addition, we addressed the involvement of TMPRSS2 and KP in this process.

The Footprint of Kynurenine Pathway in Cardiovascular Diseases

Kynurenine pathway is the main route of tryptophan metabolism and produces several metabolites with various biologic properties. It has been uncovered that several cardiovascular diseases are associated with the overactivation of kynurenine pathway and kynurenine and its metabolites have diagnostic and prognostic value in cardiovascular diseases. Furthermore, it was found that several kynurenine metabolites can differently affect cardiovascular health. For instance, preclinical studies have shown that kynurenine, xanthurenic acid and cis-WOOH decrease blood pressure; kynurenine and 3-hydroxyanthranilic acid prevent atherosclerosis; kynurenic acid supplementation and kynurenine 3-monooxygenase (KMO) inhibition improve the outcome of stroke. Indoleamine 2,3-dioxygenase (IDO) overactivity and increased kynurenine levels improve cardiac and vascular transplantation outcomes, whereas exacerbating the outcome of myocardial ischemia, post-ischemic myocardial remodeling, and abdominal aorta aneurysm. IDO inhibition and KMO inhibition are also protective against viral myocarditis. In addition, dysregulation of kynurenine pathway is observed in several conditions such as senescence, depression, diabetes, chronic kidney disease (CKD), cirrhosis, and cancer closely connected to cardiovascular dysfunction. It is worth defining the exact effect of each metabolite of kynurenine pathway on cardiovascular health. This narrative review is the first review that separately discusses the involvement of kynurenine pathway in different cardiovascular diseases and dissects the underlying molecular mechanisms.

Identification of causal metabolites related to multiple autoimmune diseases

OBJECT

Observational studies provide evidence that metabolites may be involved in the development of autoimmune diseases (ADs), but whether it is causal is still unknown.

METHODS

Based on the large-scale GWAS summary statistics, two-sample Mendelian randomization (MR) was performed to evaluate the causal association between human serum metabolites and multiple ADs, which were inflammatory bowel disease (IBD), ulcerative Colitis (UC), crohn's disease (CD), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), type 1 diabetes (T1D), multiple sclerosis (MS), primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC). Comprehensive sensitive analysis was used to validate the robustness of MR results and multivariable MR analysis was conducted to avoid potential pleiotropic effect of other complex traits. Finally, metabolic pathway analysis was performed based on causal metabolites for each ad, respectively.

RESULTS

We identified 6 causal features of metabolite after Bonferroni adjustment, i.e. glycerol 2-phosphate for T1D, hexadecanedioate, phenylacetylglutamine and laurylcarnitine for RA, glycine and arachidonate (20:4n6) for CD. Then comprehensively sensitive analysis proved the robustness of the causal associations. We also observed some overlaps of metabolites among different ADs, indicating the similar mechanisms. After controlling for several common traits, multivariable MR analysis ruled out most of potential pleiotropic effects and validated the independence of identified metabolites. Additionally, a total of 6 metabolic pathways have been identified for different ADs.

CONCLUSIONS

This study provided novel insights into investigating causal role of serum metabolites in development of multiple ADs through a comprehensive genetic pathway.