TNIK depletion induces inflammation and apoptosis in injured renal proximal tubule epithelial cells.

Abstract

In the aftermath of acute kidney injury (AKI), surviving proximal tubule epithelia repopulate injured tubules to promote repair. However, a portion of cells fail to repair [termed failed-repair proximal tubule cells (FR-PTCs)] and exert ongoing proinflammatory and profibrotic effects. To better understand the molecular drivers of the FR-PTC state, we reanalyzed a mouse ischemia-reperfusion injury single-nucleus RNA-sequencing (snRNA-seq) atlas to identify Traf2 and Nck interacting kinase (Tnik) to be exclusively expressed in FR-PTCs but not in healthy or acutely injured proximal tubules after AKI (2 and 6 wk) in mice. We confirmed expression of Tnik protein in injured mouse and human tissues by immunofluorescence. Then, to determine the functional role of Tnik in FR-PTCs, we depleted TNIK with siRNA in two human renal proximal tubule epithelial cell lines (primary and immortalized hRPTECs) and analyzed each by bulk RNA-sequencing. Pathway analysis revealed significant upregulation of inflammatory signaling pathways, whereas pathways associated with differentiated proximal tubules such as organic acid transport were significantly downregulated. TNIK gene knockdown drove reduced cell viability and increased apoptosis, including differentially expressed poly(ADP-ribose) polymerase (PARP) family members, cleaved PARP-1 fragments, and increased annexin V binding to phosphatidylserine. Together, these results indicate that Tnik upregulation in FR-PTCs acts in a compensatory fashion to suppress inflammation and promote proximal tubule epithelial cell survival after injury. Modulating TNIK activity may represent a prorepair therapeutic strategy after AKI.NEW & NOTEWORTHY The molecular drivers of successful and failed repair in the proximal tubule after acute kidney injury (AKI) are incompletely understood. We identified Traf2 and Nck interacting kinase (Tnik) to be exclusively expressed in failed-repair proximal tubule cells after AKI. We tested the effect of siTNIK depletion in two proximal tubule cell lines followed by bulk RNA-sequencing analysis. Our results indicate that TNIK acts to suppress inflammatory signaling and apoptosis in injured renal proximal tubule epithelial cells to promote cell survival.

• Authors: Shayna T J Bradford, Haojia Wu, Yuhei Kirita, Changfeng Chen, Nicole P Malvin, Yasuhiro Yoshimura, Yoshiharu Muto, Benjamin D Humphreys
• Journal: American journal of physiology. Renal physiology (Am J Physiol Renal Physiol) Vol. 326 Issue 5 Pg. F827-F838 (May 01 2024) ISSN: 1522-1466 [Electronic] United States
• PMID: 38482555 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Protein Serine-Threonine Kinases
• TNF Receptor-Associated Factor 2
• TRAF2 protein, mouse
• PSMD2 protein, human

Topics

• Kidney Tubules, Proximal (metabolism, pathology)
• Animals
• Apoptosis
• Acute Kidney Injury (metabolism, pathology, genetics)
• Epithelial Cells (metabolism, pathology)
• Humans
• Protein Serine-Threonine Kinases (metabolism, genetics)
• TNF Receptor-Associated Factor 2 (metabolism, genetics)
• Reperfusion Injury (metabolism, pathology, genetics)
• Signal Transduction
• Disease Models, Animal
• Mice
• Mice, Inbred C57BL
• Cell Line
• Inflammation (metabolism, pathology)
• Male