Urine macrophages reflect kidney macrophage content during acute tubular interstitial and glomerular injury.

Macrophage polarization is a major contributing factor in acute kidney injury (AKI). We aim to determine its biomarker value in differentiating etiologic causes of various intrinsic renal AKI. A total of 205 patients with renal intrinsic AKI were enrolled. Urinary sCD163 was quantified and macrophage subtypes in urine and in renal biopsy were determined. Compared to healthy controls and AKI due to interstitial or tubular injuries (0 pg/µmol), urinary sCD163 was markedly higher in glomerulopathy, especially in diffuse proliferative glomerulonephritis (275.5 pg/µmol) and significantly correlated with cellular crescent formation. Urine sediment analysis of M1/M2 ratio could differentiate acute tubulointerstitial nephritis (M1/M2 > 2.35) from crescentic glomerulonephritis (M1/M2 < 0.27). Urinary sCD163 levels and M2 subtype positively correlated with infiltrated M2 in the glomeruli, whereas urine M1 positively correlated with infiltrated M1 in the interstitium. Of note, urinary sCD163 showed better diagnositic performance in differentiating disease etiologies compared to tradiational urinary biomarkers of AKI (NGAL and KIM-1) and markers of myeloid cells (CD11b) and pan macrophages (CD68). Thus markers of macrophage polarization could be viewed as the noninvasive "liquid biopsy" in the presence of various intrinsic kidney diseases.

Numb Depletion Promotes Drp1-Mediated Mitochondrial Fission and Exacerbates Mitochondrial Fragmentation and Dysfunction in Acute Kidney Injury.

AIMS: Mitochondrial fragmentation is a crucial mechanism contributing to tubular cell apoptosis during acute kidney injury (AKI). However, the mechanism of modulating mitochondrial dynamics during AKI remains unclear. Numb is a multifunction adaptor protein that is expressed in renal tubules. The aim of the present study was to evaluate the role of Numb in mitochondrial dysfunction during AKI. RESULTS: The expression of Numb was upregulated in both ischemia-reperfusion- and cisplatin-induced AKI. Depletion of Numb from proximal tubules (PT-Nb-KO) exacerbated AKI shown as more severe renal tubular damage and higher serum creatinine than wild-type mice. Numb depletion alone significantly increased mitochondrial fragmentation without altering mitochondrial mass and function, including adenosine triphosphate production, mitochondrial membrane potential, oxygen consumption, and reactive oxygen species production. However, mitochondrial fragmentation and dysfunction were significantly aggravated after cisplatin exposure in PT-Nb-KO mice. Mechanistically, Numb depletion triggered dynamin-related protein 1 (Drp1) recruitment to mitochondria by increasing the phosphorylation of Drp1 at serine 656 residue (human Drp1 ser637). Inhibiting the activity of Rho-associated coiled-coil containing protein kinase (ROCK) by Y-27632 attenuated phosphorylation of Drp1 ser656 and mitochondrial fragmentation in Numb-deficient cells. Administration of mdivi-1, a pharmacological inhibitor of Drp1, restored mitochondrial morphology, attenuated cisplatin-induced tubular injury, and renal dysfunction in PT-Nb-KO mice. Innovation and Conclusion: Our data suggest that Numb depletion promotes mitochondrial fragmentation by promoting the phosphorylation of Drp1 Ser637 and thus exacerbates cisplatin-induced mitochondrial dysfunction and tubular cell apoptosis. These findings add a novel insight into modulating mechanism of mitochondrial dynamics during AKI.

HLA-DQA1, -DQB1, and -DRB1 Alleles Associated with Acute Tubulointerstitial Nephritis in a Chinese Population: A Single-Center Cohort Study.

Acute tubulointerstitial nephritis (ATIN) is a common cause of acute kidney injury with various origins. HLA-DQA1, -DQB1, and -DRB1 have been associated with development of tubulointerstitial nephritis and uveitis (TINU) syndrome in case reports and small case series, but information about HLA genetic susceptibility to drug hypersensitivity-related ATIN (D-ATIN) or other types of ATIN is limited. In this article, we genotyped 154 patients with ATIN of different causes and 200 healthy controls at HLA-DQA1, -DQB1, and -DRB1 loci. We found that there was no difference between patients with D-ATIN and TINU in the carrier's frequency of HLA-DQA1, -DQB1, or -DRB1 Patients with Sjogren's syndrome-ATIN and IgG4-related ATIN presented a different pattern of tested HLA alleles. HLA-DQA1*0104 (p value corrected by false discovery rate method [Pc] = 4.72 × 10-22, odds ratio [OR] = 13.81), -DQB1*0503 (Pc = 1.95 × 10-14, OR = 9.51), and -DRB1*1405 (Pc = 8.06 × 10-19, OR = 12.80) were significant risk alleles for the occurrence of D-ATIN and TINU. There were no significant associations between tested HLA alleles and ATIN induced by other causes. Patients with D-ATIN/TINU carrying HLA-DQA1*0104/DQB1*0503/DRB1*1405 had higher peak serum creatinine and more severe renal tubulointerstitial inflammatory impairment. They also had significantly higher levels of tubular HLA-DR and HLA-DQ expression, which were correlated with the numbers of interstitial CD4+ T lymphocytes (r = 0.975, p < 0.001 and r = 0.832, p = 0.005, respectively) and monocytes/macrophages (r = 0.721, p = 0.004 and r = 0.615, p = 0.02, respectively). In conclusion, patients with D-ATIN or TINU have genetic susceptibility in HLA-DQA1, -DQB1, and -DRB1 alleles. HLA-DQA1*0104/DQB1*0503/DRB1*1405 serves as a significant risk haplotype for development of D-ATIN and TINU, which might facilitate renal tubulointerstitial inflammation by enhancing Ag-presenting capacity of renal tubular cells.