Tryptophan catabolism via the kynurenine pathway regulates infection and inflammation: from mechanisms to biomarkers and therapies

BACKGROUND

L-Tryptophan (L-Trp), an essential amino acid, is the only amino acid whose level is regulated specifically by immune signals. Most proportions of Trp are catabolized via the kynurenine (Kyn) pathway (KP) which has evolved to align the food availability and environmental stimulation with the host pathophysiology and behavior. Especially, the KP plays an indispensable role in balancing the immune activation and tolerance in response to pathogens.

SCOPE OF REVIEW

In this review, we elucidate the underlying immunological regulatory network of Trp and its KP-dependent catabolites in the pathophysiological conditions by participating in multiple signaling pathways. Furthermore, the KP-based regulatory roles, biomarkers, and therapeutic strategies in pathologically immune disorders are summarized covering from acute to chronic infection and inflammation.

MAJOR CONCLUSIONS

The immunosuppressive effects dominate the functions of KP induced-Trp depletion and KP-produced metabolites during infection and inflammation. However, the extending minor branches from the KP are not confined to the immune tolerance, instead they go forward to various functions according to the specific condition. Nevertheless, persistent efforts should be made before the clinical use of KP-based strategies to monitor and cure infectious and inflammatory diseases.

Geriatric Phenotypes and Their Impact on Oral Health

Older adults have multiple morbidities that can impact oral, systemic, and psychological health. Although each disorder requires consideration from the provider before treatment, by assessing the common phenotypic presentations of older adults, we can better understand, select, and coordinate treatment modifications that would need to be considered and implemented for dental care.

Comparison of early postoperative cytokine changes in patients undergoing intubated and non-intubated thoracic surgery: a randomized controlled trial

OBJECTIVES

The inflammatory response after surgery is associated with patient prognosis. Patients who undergo thoracic surgery exhibit a profound systemic inflammatory response due to the surgical procedures used and application of one-lung ventilation. The aim of this study was to compare perioperative inflammatory changes in patients after intubated and non-intubated thoracic surgery for primary lung cancer resection.

METHODS

This prospective randomized controlled study included forty patients who underwent surgical resection for stage I non-small-cell lung cancer. Blood samples for cytokine analysis were collected just before induction, at 1 and 24 h after surgery. Levels of the pro-inflammatory cytokine and anti-inflammatory cytokines were measured using quantitative sandwich enzyme immunoassay kits.

RESULTS

The basal values of cytokines were comparable between 2 groups. Within each group, the postoperative levels of interleukin (IL)-1, IL-6 and tumour necrosis factor-α increased, while those of IL-4 and IL-10 did not change significantly. The levels of IL-6 and tumour necrosis factor-α were significantly lower in group NI at 1 and 24 h postoperatively. Other cytokines did not differ in both groups during postoperative period. The IL-6/IL-10 ratio at 1 h after surgery was lower in non-intubated patients than in intubated patients, but there was no difference at 24 h after surgery.

CONCLUSIONS

Non-intubated thoracic surgery may attenuate the early inflammatory cytokine changes following major resection for primary lung cancer compared with intubated conventional surgery.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov registry number NCT04007354.

High parathyroid hormone predicts exacerbations in COPD patients with hypovitaminosis D

BACKGROUND

Hypovitaminosis D has been linked to deterioration in clinical parameters and lung function in COPD. As a response to low levels of vitamin D serum Parathyroid Hormone (iPTH) is increased in some, but not all, patients. The aim of this study was to determine whether COPD patients with elevated PTH levels are at higher risk of COPD exacerbations and hospitalizations.

METHODS

166 COPD outpatients were randomly preselected. Clinical and analytical characteristics were assessed at baseline. After excluding patients with other conditions known to disturb calcium metabolism 141 patients were identified. Except one, all patients were prospectively followed for 12 months after obtaining the blood samples. Hypovitaminosis D was considered when serum 25(OH)D < 30 ng/mL. Secondary hyperparathyroidism was considered when serum iPTH was higher than normal (50 pg/mL) in patients with hypovitaminosis D. COPD exacerbations and hospital admissions were recorded during the follow-up.

RESULTS

Prevalence of hypovitaminosis D in COPD patients was 89.3%, prevalence of secondary hyperparathyroidism associated with hypovitaminosis D was 22,9%. Cox proportional risk analysis showed that patients belonging to the high iPTH-low 25(OH)D group were at a higher risk of moderate COPD exacerbations (HR 1.81 (CI95% 1.043-3.127), p = 0.035) and hospital admissions (HR 5.45 (CI95% 2.018-14.720), p = 0.002) as compared with those with normal iPTH-low 25(OH)D levels.

CONCLUSIONS

COPD patients with hypovitaminosis D and elevated iPTH have higher risk of moderate exacerbations and hospitalizations than those with hypovitaminosis D and normal iPTH.

Lymph node stromal cell subsets-Emerging specialists for tailored tissue-specific immune responses

The effective priming of adaptive immune responses depends on the precise dispatching of lymphocytes and antigens into and within lymph nodes (LNs), which are strategically dispersed throughout the body. Over the past decade, a growing body of evidence has advanced our understanding of lymph node stromal cells (LNSCs) from viewing them as mere accessory cells to seeing them as critical cellular players for the modulation of adaptive immune responses. In this review, we summarize current advances on the pivotal roles that LNSCs play in orchestrating adaptive immune responses during homeostasis and infection, and highlight the imprinting of location-specific information by micro-environmental cues into LNSCs, thereby tailoring tissue-specific immune responses.

Geriatric Phenotypes and Their Impact on Oral Health

Older adults have multiple morbidities that can impact oral, systemic, and psychological health. Although each disorder requires consideration from the provider before treatment, by assessing the common phenotypic presentations of older adults, we can better understand, select, and coordinate treatment modifications that would need to be considered and implemented for dental care.

High eosinophil blood counts are associated with a shorter length of hospital stay in exacerbated COPD patients - a retrospective analysis

Background

In COPD, the course of the disease including morbidity and mortality is strongly associated with severe exacerbations. The current GOLD recommendations emphasize blood eosinophil counts as a marker for responsiveness to inhaled corticosteroids (ICS). Retrospective analyses from randomized clinical trials indicate a favorable response to systemic corticosteroids in exacerbated COPD patients with blood eosinophils > 2%, however data outside clinical trials are scarce.

Patients and methods

We retrospectively evaluated data from 1007 cases of patients who were admitted to the University Medical Center Marburg between 01/2013 and 12/2018. All patients had been diagnosed with an acute exacerbation of COPD (ICD-10 J44.0/J44.1). Our analysis was based on a subgroup of 417 patients in whom a full blood cell count was obtained at the day of admission. Patients were predominantly male (63.3%), had a median age of 74 years (IQR 65 years – 83 years) and a median FEV1 of 1.03 l (42.6% predicted). We compared the hospital length of stay and other outcome parameters using established thresholds for the eosinophil blood cell count (100 and 300 eosinophils/μl and 2%).

Results

Patients with low eosinophils (< 2%, <100 cells/μl) had a longer median time in hospital (length of hospital stay – LOS) as compared to patients with high eosinophils (< 2%: 9.31 vs. ≥2%:7 days, and < 100/μl: 10 vs. 100–300/μl: 8 vs. > 300/μl: 7 days). The median CRP was higher in patients with low eosinophils as compared to the other groups (< 2%: 22.7 vs. ≥2%: 9 mg/dl and < 100: 25 vs. 100–300: 13.5 vs. > 300: 7.1 mg/dl). Time to re-hospitalization or time to death did not differ between strata of eosinophils. Sensitivity analysis in a subgroup of patients in which pneumonia was excluded by chest x-ray did not significantly alter the results.

Conclusion

The results support the hypothesis that patients with severe COPD exacerbations and elevated blood eosinophil counts respond better to systemic corticosteroid treatment than patients with a non-eosinophilic exacerbation.

Impact of gram negative bacteria airway recolonization on the occurrence of chronic lung allograft dysfunction after lung transplantation in a population of cystic fibrosis patients

Background

Chronic Lung Allograft Dysfunction (CLAD) is the main cause of morbidity and mortality after the first year following lung transplantation (LTx). Risk factors of CLAD have been extensively studied, but the association between gram-negative bacteria (GNB) bronchial colonization and the development of CLAD is controversial. The purpose of our study was to investigate the association between post-transplant recolonization with the same species or de-novo colonization with a new GNB species and CLAD. The same analysis was performed on a sub-group of patients at the strain level using Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry technique.

Results

Forty adult cystic fibrosis (CF) patients who underwent a first bilateral LTx in the University Hospital of Marseille, between January 2010 and December 2014, were included in the study. Patients with GNB de-novo colonization had a higher risk of developing CLAD (OR = 6.72, p = 0.04) and a lower rate of CLAD-free survival (p = 0.005) compared to patients with GNB recolonization. No conclusion could be drawn from the subgroup MALDI-TOF MS analysis at the strain level.

Conclusion

Post-LTx GNB airway recolonization seems to be a protective factor against CLAD, whereas de-novo colonization with a new species of GNB seems to be a risk factor for CLAD.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1231-7) contains supplementary material, which is available to authorized users.

The association between Staphylococcus aureus and subsequent bronchiectasis in children with cystic fibrosis

BACKGROUND

Staphylococcus aureus (S. aureus) may be related to more rapid progression of cystic fibrosis (CF) lung disease.

METHODS

In the AREST CF cohort study, children diagnosed with CF undergo annual bronchoscopies with bronchoalveolar lavage and ultra-low-dose, chest computed tomography (CT) up to 6-years-old. Spirometry was assessed 3-monthly from the age of 4years. Associations between de novo S. aureus acquisition before school age and CT and lung function at ages 5-7years were investigated. Models were adjusted for multiple markers of disease severity at baseline.

RESULTS

De novo S. aureus acquisition at 3-years-old (n/N=12/122) was associated with increased bronchiectasis score at age 5-6years. This association decreased but remained significant after adjustment for confounders. S. aureus at 3 was associated with significantly reduced FEF_25-75 at age 5-7years, but not with FEV₁-%-predicted.

CONCLUSION

De novo S. aureus acquisition at age 3 is associated with later bronchiectasis and FEF_25-75 in children with CF.

Treatment delay and fatal outcomes of pulmonary tuberculosis in advanced age: a retrospective nationwide cohort study

BACKGROUND AND OBJECTIVE

Studies focusing on pulmonary tuberculosis in advanced age (≥80 years) are lacking. This study aimed to explore treatment delay, outcomes and their predictors in this group.

METHODS

Adult (≥20 years) patients with pulmonary tuberculosis were identified from the National Health Insurance Research Database of Taiwan from 2004 to 2009. Treatment completion and mortality rates were noted at one year after treatment.

RESULTS

Among the 81,081 patients with pulmonary tuberculosis identified, 13,923 (17.2%) were aged ≥80 years, and 26,897 (33.2%) were aged 65-79 years. The treatment completion, mortality rates and treatment delay were 54.8%, 34.7% and 61 (12-128) [median, (1st-3rd quartiles)] days in patients aged ≥80 years, 68.3%, 18.5% and 53 (8-122) days in patients aged 65-79 years, and 78.9%, 6.5% and 21 (1-84) days in patients aged <65 years, respectively. The elder patients were more likely to receive second-line anti-tuberculosis agents. The treatment completion rate decreased with older age, female sex, comorbidities, low income, requiring second-line anti-tuberculosis agents, severity of pulmonary tuberculosis and longer treatment delay. Older age, female sex, comorbidities, low income, and not undergoing rapid molecular diagnostic tests were independently associated with longer treatment delays.

CONCLUSIONS

Pulmonary tuberculosis in advanced age has a longer treatment delay and a higher mortality rate. Applying rapid molecular diagnostic tools may reduce treatment delay and should be integrated into the diagnostic algorithm for pulmonary tuberculosis, particularly in elderly patients.

Primary graft dysfunction: Long-term physical function outcomes among lung transplant recipients

BACKGROUND

Adults with primary graft dysfunction (PGD) after lung transplantation are at increased risk for pulmonary and functional impairment. No prior studies have described the long-term (within 1.5 years of transplant) cardiopulmonary exercise testing (CPET) results in adults with grade 3 PGD. The objective of this study was to compare the functional outcomes of lung transplant patients with and without grade 3 PGD via CPET and six-minute talk tests (6MWD).

METHODS

243 adults underwent lung transplantation between 2003 and 2010, 128 (53%) of whom underwent CPET and 6MWD within 12-18 months of transplantation. The primary measure of exposure was grade 3 PGD at 72 h, however grade 3 PGD within 72 h was also assessed. In addition, the impact of potential confounding variables was explored.

RESULTS

Approximately one-third (32%) of the 243 patients experienced grade 3 PGD within 72 h; among these, 15 (6%) had grade 3 PGD at the 72 h time point. There were no differences in CPET or 6MWD between those with and without grade 3 PGD at 72 h despite a longer length of hospital stay and lower pulmonary function. Similar results were seen for patients with and without grade 3 PGD within 72 h, with the exception of a lower heart rate on CPET.

CONCLUSIONS

Participants with grade 3 PGD are able to achieve functional outcomes comparable to those without PGD.