Indoleamine 2,3-Dioxygenase (IDO) Enzyme Links Innate Immunity and Altered T-Cell Differentiation in Non-ST Segment Elevation Acute Coronary Syndrome

The role of the kynurenine pathway in cardiovascular disease

The kynurenine pathway (KP) serves as the primary route for tryptophan metabolism in most mammalian organisms, with its downstream metabolites actively involved in various physiological and pathological processes. Indoleamine 2,3-dioxygenase (IDO) and tryptophan 2,3-dioxygenase (TDO) serve as the initial and pivotal enzymes of the KP, with IDO playing important and intricate roles in cardiovascular diseases. Multiple metabolites of KP have been observed to exhibit elevated concentrations in plasma across various cardiovascular diseases, such as atherosclerosis, hypertension, and acute myocardial infarction. Multiple studies have indicated that kynurenine (KYN) may serve as a potential biomarker for several adverse cardiovascular events. Furthermore, Kynurenine and its downstream metabolites have complex roles in inflammation, exhibiting both inhibitory and stimulatory effects on inflammatory responses under different conditions. In atherosclerosis, upregulation of IDO stimulates KYN production, mediating aromatic hydrocarbon receptor (AhR)-induced exacerbation of vascular inflammation and promotion of foam cell formation. Conversely, in arterial calcification, this mediation alleviates osteogenic differentiation of vascular smooth muscle cells. Additionally, in cardiac remodeling, KYN-mediated AhR activation exacerbates pathological left ventricular hypertrophy and fibrosis. Interventions targeting components of the KP, such as IDO inhibitors, 3-hydroxyanthranilic acid, and anthranilic acid, demonstrate cardiovascular protective effects. This review outlines the mechanistic roles of KP in coronary atherosclerosis, arterial calcification, and myocardial diseases, highlighting the potential diagnostic, prognostic, and therapeutic value of KP in cardiovascular diseases, thus providing novel insights for the development and application of related drugs in future research.

Human peripheral blood mononuclear cells display a temporal evolving inflammatory profile after myocardial infarction and modify myocardial fibroblasts phenotype

Pathophysiological response after acute myocardial infarction (AMI) is described as a three-stage model involving temporal phenotypic modifications of both immune cells and fibroblasts: a primary inflammatory phase, followed by a reparative phase and a fibrous scar maturation phase. Purinergic receptors, particularly the P2Y11 receptor, have been reported to be involved in the regulation of inflammation after ischemia and could act for the resolution of inflammation after AMI. For the first time, we characterized the immuno-inflammatory and P2Y11 expression profiles of peripheral blood mononuclear cells (PBMC) from AMI patients and analyzed the consequences of presenting these cells to cardiac fibroblasts in vitro. PBMC from 178 patients were collected at various times after reperfused ST-segment elevation AMI, from H0 to M12. Expression level of P2RY11 and genes involved in tolerogenic profile of dendritic cells and T cell polarization were evaluated by RT-PCR. P2Y11 protein expression was assessed by flow cytometry. PBMC and human cardiac fibroblasts (HCF) were cocultured and α-SMA/vimentin ratio was analyzed by flow cytometry. Within the first 48 h after AMI, expression levels of HMOX1, STAT3 and CD4 increased while IDO1 and TBX21/GATA3 ratio decreased. Concomitantly, the expression of P2RY11 increased in both T and B cells. In vitro, PBMC collected at H48 after AMI induced an increase in α-SMA/vimentin ratio in HCF. Our results suggest that human PBMC display an evolving inflammatory profile with reparative characteristics the first two days after AMI and secrete soluble mediators leading to the fibroblastic proteins modification, thus participating to myocardial fibrosis.

The Tryptophan and Kynurenine Pathway Involved in the Development of Immune-Related Diseases

The tryptophan and kynurenine pathway is well-known to play an important role in nervous, endocrine, and immune systems, as well as in the development of inflammatory diseases. It has been documented that some kynurenine metabolites are considered to have anti-oxidative, anti-inflammatory, and/or neuroprotective properties. Importantly, many of these kynurenine metabolites may possess immune-regulatory properties that could alleviate the inflammation response. The abnormal activation of the tryptophan and kynurenine pathway might be involved in the pathophysiological process of various immune-related diseases, such as inflammatory bowel disease, cardiovascular disease, osteoporosis, and/or polycystic ovary syndrome. Interestingly, kynurenine metabolites may be involved in the brain memory system and/or intricate immunity via the modulation of glial function. In the further deliberation of this concept with engram, the roles of gut microbiota could lead to the development of remarkable treatments for the prevention of and/or the therapeutics for various intractable immune-related diseases.

Dynamic changes of monocytes subsets predict major adverse cardiovascular events and left ventricular function after STEMI

We explored how dynamic changes in monocyte subset counts (as opposed to static values to specific time points), and their phagocytic and NFκB activity relate to major adverse cardiovascular events (MACE) and left ventricular ejection fraction (LVEF) in patients with ST-elevation myocardial infarction (STEMI). Changes in counts, phagocytic activity and intracellular levels of inhibitory κB kinase β (IKKβ) (a marker of NFκB activity) of monocyte subsets (CD14⁺⁺CD16^-CCR2⁺ [Mon1], CD14⁺⁺CD16⁺CCR2⁺ [Mon2] and CD14⁺CD16⁺⁺CCR2^- [Mon3]) were measured by flow cytometry in patients with STEMI at baseline, and again after one week, two weeks, and one month. LVEF was measured by echocardiography at baseline and six months after STEMI. Baseline data included 245 patients (mean ± SD age 60 ± 12 years; 22% female), who were followed for a median of 46 (19-61) months. Multivariate Cox regression demonstrated that more prominent dynamic reduction in Mon2 by week 1 (n = 37) was independently associated with fewer MACE (HR 0.06, 95% CI 0.01-0.55, p = 0.01). Also, less prominent reduction in Mon2 at month 1 (n = 24) was independently predictive of 6-month LVEF. None of the other dynamic changes in monocyte subsets were associated with changes in survival from MACE. Neither phagocytic activity nor IKKβ were associated with survival for each monocyte subset. We showed how distinct pattern of dynamic changes in Mon2 are related to both MACE risk and recovery of cardiac contractility. Further research is needed to understand the mechanism of the monocyte effect and possibilities of their pharmacological manipulation.

Untargeted metabolomics identified kynurenine as a predictive prognostic biomarker in acute myocardial infarction

OBJECTIVE

The occurrence of cardiovascular adverse events in the first year after ST-acute myocardial infarction (STEMI) remains high; therefore, identification of patients with poor prognosis is essential for early intervention. This study aimed to evaluate the prognostic value of metabolomics-based biomarkers in STEMI patients and explore their functional mechanisms.

METHODS

Metabolite profiling was performed using nuclear magnetic resonance. The plasma concentration of Kynurenine (Kyn) was measured using ultraperformance liquid chromatography/electrospray ionization quadruple time-of-flight mass spectrometry. Major adverse cardiac and cerebral events were assessed for 1 year. A functional metabolomics strategy was proposed for investigating the role of Kyn in both vitro and vivo models.

RESULTS

The adjusted hazard ratios in STEMI patients for Kyn in the 4^th quartile 7.12(5.71-10.82) was significantly higher than that in the 3^rd quartile 3.03(2.62-3.74), 2^nd quartile 1.86(1.70-2.03), and 1^st quartile 1.20(0.93-1.39).The incidence of MACCE was significantly different among Kyn quartiles and the highest incidence of MACCE was observed in the 4th quartile when compared with the 1st quartile (9.84% vs.2.85%, P<0.001).Immunofluorescence staining indicated that indoleamine-pyrrole 2,3-dioxygenase (IDO1) was located in the CD68 positive staining area of thrombi from STEMI patients and Kyn was induced in the early phase after myocardial infarction. Kyn could trigger inflammation and oxidative stress of macrophage cells by activation of the Sirt3-acSOD2/IL-1β signaling pathway in vitro.

CONCLUSIONS

Plasma Kyn levels were positively associated with the occurrence of STEMI. Kyn could induce macrophage cells inflammation and oxidative stress by activating the Sirt3-acSOD2/IL-1β pathway following myocardial ischemia injury. Kyn could be a robust biomarker for STEMI prognosis and reduction of Kyn could be beneficial in STEMI patients.

Th17/Treg balance and indoleamine 2,3 dioxygenase activity in periodontitis-associated atherosclerotic patients

Objective

This study investigated the peripheral Th17/Treg balance and its potential controlling factor indoleamine 2,3 dioxygenase (IDO) in patients with periodontitis and atherosclerosis (AS), as well as its correlation with Porphyromonas gingivalis infection.

Methods

In this retrospective study, P. gingivalis-infected atherosclerotic patients (Pg-AS), atherosclerotic patients (AS), P. gingivalis-infected periodontitis patients (Pg), and healthy controls (HCs) were selected after clinical examination, subgingival plaque examination, and plasma anti-P. gingivalis antibody analysis. Treg and Th17 cell percentages, related transcription factors, and functional cytokines in peripheral blood were analysed. Plasma tryptophan (Trp) and kynurenine (Kyn) were measured to determine IDO activity.

Results

Atherosclerotic patients (Pg-AS and AS groups) had significantly lower IDO activity and higher Th17/Treg ratio than those in the Pg and HC groups. The Th17/Treg ratio was higher and IDO activity was lower in the Pg-AS group compared with the AS group. Transcription factors and cytokines exhibited the same trend as the Th17 and Treg cells. Additionally, IDO activity was negatively correlated with the plasma anti-P. gingivalis antibody titre and the Th17/Treg ratio in the atherosclerotic group.

Conclusions

P. gingivalis may reduce IDO activity and further promote Th17/Treg imbalance to facilitate AS development. IDO may be a novel molecular marker to predict periodontitis-associated AS.

Metabolomic Profile and Antioxidant/Anti-Inflammatory Effects of Industrial Hemp Water Extract in Fibroblasts, Keratinocytes and Isolated Mouse Skin Specimens

Industrial hemp is a multiuse crop whose phytocomplex includes terpenophenolics and flavonoids. In the present study, the phenolic and terpenophenolic compounds were assayed in the water extract of the hemp variety Futura 75. Protective effects were also investigated in human fibroblast and keratinocytes and isolate mouse skin specimens, which were exposed to hydrogen peroxide and/or to the extract (1-500 µg/mL). The results of phytochemical analysis suggested the cannabidiol, cannabidiolic acid and rutin as the prominent phytocompounds. In the in vitro system represented by human keratinocytes and fibroblasts, the hemp extract was found to be able to protect cells from cytotoxicity and apoptosis induced by oxidative stress. Moreover, modulatory effects on IL-6, a key mediator in skin proliferation, were found. In isolated rat skin, the extract reduced hydrogen peroxide-induced l-dopa turnover, prostaglandin-E2 production and the ratio kynurenine/tryptpophan, thus corroborating anti-inflammatory/antioxidant effects. The in silico docking studies also highlighted the putative interactions between cannabidiol, cannabidiolic acid and rutin with tyrosinase and indoleamine-2,3-dioxygenase, involved in l-dopa turnover and tryptophan conversion in kynurenine, respectively. In conclusion, the present findings showed the efficacy of hemp water extract as a skin protective agent. This could be partly related to the extract content in cannabidiol, cannabidiolic acid and rutin.

Water Extract from Inflorescences of Industrial Hemp Futura 75 Variety as a Source of Anti-Inflammatory, Anti-Proliferative and Antimycotic Agents: Results from In Silico, In Vitro and Ex Vivo Studies

Industrial hemp (Cannabis sativa) is traditionally cultivated as a valuable source of fibers and nutrients. Multiple studies also demonstrated antimicrobial, anti-proliferative, phytotoxic and insecticide effects of the essential oil from hemp female inflorescences. On the other side, only a few studies explored the potential pharmacological application of polar extracts from inflorescences. In the present study, we investigated the water extract from inflorescences of industrial hemp Futura 75 variety, from phytochemical and pharmacological point of view. The water extract was assayed for phenolic compound content, radical scavenger/reducing, chelating and anti-tyrosinase effects. Through an ex vivo model of toxicity induced by lipopolysaccharide (LPS) on isolated rat colon and liver, we explored the extract effects on serotonin, dopamine and kynurenine pathways and the production of prostaglandin (PG)E₂. Anti-proliferative effects were also evaluated against human colon cancer HCT116 cell line. Additionally, antimycotic effects were investigated against Trichophyton rubrum, Trichophyton interdigitale, Microsporum gypseum. Finally, in silico studies, including bioinformatics, network pharmacology and docking approaches were conducted in order to predict the putative targets underlying the observed pharmacological and microbiological effects. Futura 75 water extract was able to blunt LPS-induced reduction of serotonin and increase of dopamine and kynurenine turnover, in rat colon. Additionally, the reduction of PGE₂ levels was observed in both colon and liver specimens, as well. The extract inhibited the HCT116 cell viability, the growth of T. rubrum and T. interdigitale and the activity of tyrosinase, in vitro, whereas in silico studies highlighting the inhibitions of cyclooxygenase-1 (induced by carvacrol), carbonic anhydrase IX (induced by chlorogenic acid and gallic acid) and lanosterol 14-α-demethylase (induced by rutin) further support the observed pharmacological and antimycotic effects. The present findings suggest female inflorescences from industrial hemp as high quality by-products, thus representing promising sources of nutraceuticals and cosmeceuticals against inflammatory and infectious diseases.

Changes of peripheral blood immune cells in acute coronary syndrome

The objective of this study is to explore changes in main immune cells during acute coronary syndrome (ACS), including changes in subsets of monocytes, T cells, and inhibitory myeloid-derived suppressor cells (MDSCs), and to evaluate possible mechanisms. A total of 50 patients suffering from ACS were divided into two subgroups based on attacks of acute infarction, acute myocardial infarction (AMI) with infarction including ST-segment elevation myocardial infarction (STEMI), non-ST-segment elevation myocardial infarction (NSTEMI), and unstable angina (UA). Third, the subgroup of 19 healthy subjects was labeled the normal group (NG). CD14, CD16, and CD45 were used as markers of the subset of monocytes. CD4, CD8, and CD3 were used as markers of the subset of T cells and CD14, human leukocyte antigen—DR isotype (HLA-DR), and CD45 were used as markers of inhibitory MDSCs. Both CD11b+ CD206+ and CD11b+ CD68+ cells were also assayed. Our data indicated that lymphocytes/karyocytes and monocytes/karyocytes as well as those of CD3+ CD4+ T cells, CD14+ CD16– monocytes, CD14+ CD16+ monocytes, and CD11b+ CD68+ monocytes were significant in all three groups ( P < 0.05). The ratio of T-cell subtypes to total lymphocytes among the three subgroups can be represented as AMI > UA > NG ( P < 0.05). The ratios of CD14+ monocytes to total karyocytes among the three subgroups can be represented as NG > UA > AMI ( P < 0.05). The ratios of CD14+ CD16– monocytes to total karyocytes among the three subgroups can be represented as NG > UA > AMI ( P < 0.05). The ratios of CD14+ CD16+ monocytes to total karyocytes among the three subgroups can be represented as AMI > UA > NG ( P < 0.05). There were no significant differences in the proportion of MDSCs ( P > 0.05). Certain subsets of monocytes are closely associated with ACS, of which CD14+ CD16– monocytes present a negative association, while CD14+ CD16+ monocytes show a positive association. In addition, adaptive immunity is associated with unstable plaques of ACS, and CD3+ CD4+ T cells may play a role in early stages of ACS.