132. Roles of Transglutaminase, Protein Crosslinking Enzyme, in Antibody-mediated Glomerulonephritis
Creators: name: Ito1, Yoshimasa
name: Umeda1, Ryosuke
name: Tatsukawa2, Hideki
name: Takahashi3, Kazuo
name: Hitomi2, Kiyotaka
name: Naotake Tsuboi1
Publisher: name: Zenodo
Year: 2022
Subjects: Vasculitis
ANCA
Abstracts
Giant Cell Arthritis
MPA
GPA
EGPA
Takayasu
IgA vasculitis

description: <strong>Background:</strong> Transglutaminase (TGase) is an enzyme that catalyses the covalent bond between glutamine and lysine residue of proteins in on Ca<sup>2+</sup> dependent manner. TG2, an isozyme of TGases, is expressed in glomerular and proximal tubular cells and is well known to promote extracellular matrix accumulation leading to the progression of kidney fibrosis. TG2 null mouse (TG2KO) exhibited normal development and postnatal growth. The elevated TG2 expression in glomerulus has been observed in human kidney specimen of IgA nephropathy, or in animal models such as rat diabetic nephropathy and mouse antibody-mediated glomerulonephritis (GN). Recently, we have reported that the distribution of TG2 expression does not correlate with its activity. To elucidate roles of TG2 in GN, we analysed TG2 expression in crescentic GN of wild type (WT) and TG2 null (TG2KO) mice and in glomerular cells in response to several inflammatory stimuli. <strong>Methods</strong>: Necrotizing crescentic GN was induced by intravenous injection of nephrotoxic serum in pre-immunized mice with rabbit IgG (NTS-GN). Renal function and histology were assessed in TG2 null (TG2KO) and wild type (WT) mice. TG2 activity was visualized using TG2 specific substrate peptide labelled with FITC (FITC-pepT26, HQSYVDPWMLDH). Glomerular TG2 activity was evaluated by fluorescent intensity and quantified using Image J software (NIH). Glomerular disease activity was semi-quantified by Periodic Acid-Schiff (PAS) positive index from the average of 20 glomeruli (ratio of PAS positive area in a glomerulus; 0%, 0; 0-25%, 1; 25-50%, 2; 50-75%, 3; 75-100%, 4). Cellular TG2 expressions were detected by immunoblot analysis in immobilized mouse mesangial cells (MES13) and vascular endothelial cells (RCB1994) in response to tumour necrosis factor-α (TNF-α) and lipopolysaccharide (LPS). Statistical analyses were used with Student’s t test or Wilcoxon rank sum test. If the p-value was less than or equal to 0.05, the result was accepted as statistically significant. <strong>Results:</strong> TG2KO demonstrated severe proteinuria (258.6±243.6 vs 118.6±109.0 mg/gCr, p&lt;0.05) and comparable histological glomerular injury compared to WT in initial phase of NTS-GN. On the other hand, severe proteinuria (182.3±156.6 vs 128.0±19.5 mg/gCr, p=0.42) and glomerular injury were observed in advanced phase of NTS-GN. Change of body weight from the baseline and BUN were not significantly different between TG2KO and WT. During the observation period, some of the TG2KO mice died. In WT, the glomerular TG2 activity was remarkably elevated in initial phase of the disease without the histological changes, and it was hardly detected in sclerotic glomeruli. TG2 expression in MES13 was elevated in response to LPS stimulation, but not to TNF-α stimulation. On the other hand, elevated TG2 expression was observed in RCB1994 upon stimulation with both TNF-α and LPS. <strong>Conclusions:</strong> Our data suggested that TG2 activity associates with primary inflammation and may have a protective role against the onset of NTS-GN, and that exogenous inflammatory signals that induce TG2 expression are diverse in glomerular cell types. <strong>Disclosures:</strong> None.