Urinary neopterin and kynurenine in patients submitted to surgical stress with different inhalational anesthetics (halothane or isoflurane)

Measuring the Systemic Inflammatory Response to On- and Off-Pump Coronary Artery Bypass Graft (CABG) Surgeries Using the Tryptophan/Kynurenine Pathway

Background: Cardiac surgeries induce many inflammatory responses with remarkable clinical implications. Tryptophan (Trp) is a precursor for serotonin, melatonin and kynurenine (Kyn). Plasma kynurenic acid (Kyna) and Kyn concentrations are thought to be related to the severity of inflammation. Plasma Trp/Kyn ratio is used to measure inflammatory cytokine activity.Methods: We performed the current longitudinal study in a tertiary care center and included 62 patients divided into two groups; group A (on-pump CABG patients) and group B (off-pump CABG patients). Plasma Trp and Kyn were measured using the high-performance liquid chromatography (HPLC) technique. Serum interlukin-6 (IL-6) and white blood cells (WBCs) were measured using ELISA and routine blood count, respectively.Results: The present study revealed that the intraoperative levels of plasma Kyn, IL-6 and WBCs were significantly increased while the plasma Trp/Kyn ratio was significantly decreased in both the groups; however, the changes were more significant in the on-pump CABG group. Moreover, the levels in both the groups returned to preoperative levels 72 h postoperative. Our study has shown that WBCs is positively correlated with IL-6, but has negative correlation with Trp/Kyn ratio.Conclusions: Kyn and Trp/Kyn ratio might be utilized as markers of the severity of inflammation in major surgery. In addition, off-pump CABG might be more preferable than on-pump CABG regarding stress and release of inflammatory markers.

Knee replacement surgery significantly elevates the urinary inflammatory biomarkers neopterin and 7,8-dihydroneopterin

CONTEXT

Knee arthroplasty surgery is significant trauma, leading to an activated immune system causing inflammation and oxidative stress. Many current biomarkers are invasive, costly, and often slow to analyse, limiting their use for rapid inflammatory measurements.

OBJECTIVES

We have examined the use of urinary neopterin and total neopterin in knee arthroplasty patients to non-invasively measure oxidative stress and inflammation from immune system activation. We aim to validate the use of these biomarkers for quick, cost effective and predictive measurements of post-surgical inflammation assessment.

METHODOLOGY

19 Knee arthroplasty patients were analysed pre-operatively and for a defined post-operative period to determine the urinary levels of neopterin and total neopterin (neopterin +7,8-dihydroneopterin) using high performance liquid chromatography with fluorescence detection. These results were then compared to a control group of 20 participants with normal knee function.

RESULTS

7,8-Dihydroneopterin was stable in urine over 12 h when refrigerated. Knee arthritis was associated with an increase in pre-operative neopterin (oxidative stress) and total neopterin (inflammation). The subsequent arthroplasty surgery generated a significant increase neopterin and total neopterin. Both biomarkers were reduced immediately post-operatively, before becoming elevated on the following days. There was no clear evidence of an association between initial neopterin and total neopterin levels and a patient's level of inflammation during in-hospital recovery.

CONCLUSIONS

The stability of 7,8-dihydroneopterin in urine allows for its use as an inflammatory marker. Urinary neopterin and total neopterin provided a fast, non-invasive, and simple measure of oxidative stress and inflammation after knee arthroplasty.

Plasma kynurenic acid concentration in patients undergoing cardiac surgery: effect of anaesthesia

Increases in plasma kynurenic acid (KYNA) concentration relate to the severity of inflammation. The aim of this study was to analyse changes in plasma KYNA concentration and neutrophil/lymphocyte ratio (NLR) in cardiac surgery patients. Additionally, the effect of anaesthesia was analysed. Adult cardiac surgery patients under intravenous general anaesthesia were studied. Additionally, some patients received sevoflurane (SEV) prior to cardiopulmonary bypass. Plasma KYNA concentration and NLR were measured before anaesthesia, just after surgery and on postoperative days 1, 2 and 3. Patients were assigned to two groups: patients who did not receive SEV (NonSEV group) and patients who received SEV (SEV group). Forty-three patients were studied. Twenty-four of them received SEV. KYNA increased immediately after surgery and remained elevated through postoperative day 3 in the NonSEV group, whereas it was similar to the preoperative concentration in the SEV group. NLR increased immediately after surgery in both groups, and higher values were noted in the NonSEV group than in the SEV group at postoperative days 2 and 3. Plasma KYNA concentration correlated with NLR in the NonSEV group. Cardiac surgery caused an increase in NLR. Plasma KYNA increased in the NonSEV group and correlated with NLR. Administration of SEV inhibited the increase in KYNA, most likely due to its anti-inflammatory properties.

Immunosuppression routed via the kynurenine pathway: a biochemical and pathophysiologic approach

In the past years, it has been shown that kynurenines pathway is a regulator of both the innate and the adaptive immune responses. Particularly, the initial enzyme of this pathway, indoleamine 2,3-dioxygenase (IDO), is implicated in maintaining tolerance during pregnancy, and also can be expressed in tumors to avoid the immune attack. In this chapter, we will describe how the kynurenine pathway affects the immune system with important implications both in physiology and in pathology. The incorrect activation or blockade suppressive properties of the kynurenine pathway are also implicated in a number of other diseases such as AIDS or autoimmune diseases.