Kazuo Takahashi

Tryptophan (TRP) metabolism through the kynurenine pathway generates multiple biologically active metabolites with diverse immunomodulatory effects, but their roles in glomerulonephritis (GN), particularly in innate immunity, remain poorly understood. Using a nephrotoxic serum-induced GN (NTS-GN) model, we first analyzed mice deficient in key TRP-metabolizing enzymes of the kynurenine pathway: Indoleamine 2,3-dioxygenase 1 and 2 (IDO1 and IDO2), and kynurenine 3-monooxygenase (KMO), and found that Ido1-deficient mice exhibited exacerbated kidney injury and glomerular neutrophil infiltration, whereas Ido2 deficiency had no significant impact. In contrast, Kmo-deficient mice showed reduced crescent formation. Unexpectedly, the concentration of kynurenic acid (KYNA), a downstream metabolite of IDO1, was elevated in the kidney cortex of Ido1-deficient mice. Exogenous KYNA administration improved survival, ameliorated renal injury, and reduced neutrophil infiltration in Ido1-deficient mice, indicating its protective effect against antibody-mediated injury. Moreover, KYNA suppressed immune complex-mediated neutrophil spreading, attenuated FcγR-dependent Syk phosphorylation, and reduced VEGF secretion in vitro. Our results position KYNA as a key modulator of neutrophil-driven inflammation in antibody-mediated GN. This study uncovers distinct roles for kynurenine pathway enzymes and highlights the TRP-KYNA pathway as a promising immunometabolic target for controlling innate immune responses in GN.

Structural variations of N-glycans critically regulate glycoprotein functions and are involved in various human diseases. N-Acetylglucosaminyltransferase-III (GnT-III or MGAT3) is highly expressed in the brain and kidney and is an N-glycan branching enzyme that biosynthesizes the unique N-glycan branch designated as bisecting GlcNAc. Its roles in Alzheimer's disease and cancer have been revealed, but the functions of bisecting GlcNAc in the kidney are poorly understood. Here, we show that kidneys in the GnT-III-knockout (KO) mouse exhibit impaired body fluid balance and present interstitial edema. To understand the molecular mechanisms further, we biochemically purified the glycoproteins modified by GnT-III in the mouse kidney and identified these proteins using proteomics. We found that the proteins involved in the pathway for angiotensin II (Ang II) metabolism are modified by GnT-III, and that the subcellular localization of angiotensin-converting enzyme was altered in GnT-III-KO cells. Furthermore, the pathology in models of Ang II-related disease was slightly more severe in GnT-III-KO than in wild-type mice. Our data indicate a protective role for bisecting GlcNAc in the mouse kidney, highlighting a newly described link between specific N-glycan structures and renal functions.

OBJECTIVES: Sivelestat sodium hydrate (SSH) may be effective in the early stage of acute respiratory distress syndrome (ARDS) before the neutrophil extracellular trap scaffold structure is complete. Therefore, patients with suppression of fibrinolysis (SF) before the secondary fibrinolytic process might benefit from SSH administration. The primary aim of this study was to determine the effect of the SF state and combination therapy on the effect of SSH administration. METHODS: We retrospectively reviewed the data of patients diagnosed with ARDS at Fujita Health University Hospital between July 2005 and December 2016. Patients with ARDS were stratified into the SF and hyperfibrinolysis (HF) groups. Using the fibrin degradation product (FDP)/D-dimer ratio, cut-off values were set as follows: FDP/D-dimer >2 for the HF group and FDP/D-dimer ≤2 for the SF group. The 28-day mortality was the primary endpoint. RESULTS: In total, 168 patients (71 in the HF group and 97 in the SF group) were included in the analysis. The mortality within 28 days was not different based on SSH administration in either group (HF group: p=0.956, SF group: p=0.957). In the SF group, the mortality rate within 28 days in SSH-treated patients who received antithrombotic drugs was significantly higher than that in patients who received SSH only (p<0.05). However, this finding was not present in the HF group (p=0.786). CONCLUSIONS: Concomitant use of SSH and antithrombotic drugs might worsen the treatment outcome of patients with ADRS in the SF state.

BACKGROUND: IgA nephropathy (IgAN) is the most common type of primary glomerulonephritis. Elevation in the blood levels of aberrantly glycosylated IgA1 is a crucial initial step in IgAN pathogenesis. Here, we aimed to determine the longitudinal changes in the serum levels of IgA1 O- and N-glycoforms in patients with IgAN receiving different treatments. METHODS: We enrolled Japanese patients diagnosed with primary IgAN: 10 patients who underwent tonsillectomy and corticosteroid therapy (T-CST), 7 who received corticosteroid therapy (CST), 8 who received conservative therapy (CO), and 5 with other renal diseases who received corticosteroid therapy (ORD) as disease controls. IgA was purified from patient sera collected at diagnosis and post-treatment. After sample preparation, O-glycoforms of the hinge region (HR) and N-glycoforms of the fragment crystallizable region were analyzed using high-resolution mass spectrometry (MS). RESULTS: The MS analysis of O-glycoforms of IgA1 showed that the relative abundance of IgA1 with 3GalNAc3Gal, which we previously identified as a characteristic IgA1 O-glycoform in IgAN, decreased post-treatment only in the T-CST group (P = 0.0195). Regarding N-glycoforms, the relative abundance of fucosylated N-glycan at asparagine (Asn)340 increased in the IgAN group compared with that in the ORD group (P = 0.0189) and decreased post-treatment only in the T-CST group (P = 0.0195). CONCLUSION: The MS analysis of O- and N-glycoforms of IgA1 revealed substantial changes in their abundance in the T-CST group but not in the CST, CO, and ORD groups. Our study provides new insights into how specific treatments alter the IgA1 glycoform abundance.

BACKGROUND/AIM: Effective monitoring of antibiotic use is essential for antimicrobial stewardship. While Days of Therapy (DOT) is commonly used to assess antibiotic consumption, it does not fully capture changes in antimicrobial spectrum during de-escalation. To address this, the Days of Antibiotic Spectrum Coverage (DASC) metric-calculated using a spectrum score weighted by antimicrobial breadth-was developed. This study aimed to evaluate the utility of DASC in identifying trends in antibiotic de-escalation across hospital wards and to determine whether it can serve as a reliable metric for assessing the appropriateness of antibiotic use at the departmental level. PATIENTS AND METHODS: This single-center retrospective study was conducted at an acute care community hospital in Japan, which has 21 clinical departments and 250 inpatient beds, including four intensive care unit beds. We retrospectively analyzed trends in inpatient antimicrobial use from May 2019 to March 2023 using DASC to assess the effectiveness of a newly instituted antimicrobial stewardship program. RESULTS: DASC/DOT in the Otolaryngology and respiratory medicine wards showed a significant decreasing trend, but a significant increase was observed in both the surgery and general practice wards. We observed no significant trends in the other wards. In the surgery and respiratory medicine wards, broad-spectrum antimicrobials such as carbapenems were frequently used. CONCLUSION: DASC highlighted differences in the trends of antimicrobial de-escalation at the ward level and identified targets for antimicrobial stewardship intervention.