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Possible involvement of tubular interleukin-34 in macrophage recruitment during colistin-induced nephrotoxicity in
Kohei Matsushita1, Hirotoshi Akane1, Jun-Ichi Akagi1
1Division of Pathology, National Institute of Health Sciences.
Abstract:
Colistin is a cationic cyclic lipopeptide antibiotic used against multidrug-resistant Gram-negative bacteria; however, its clinical application is limited by nephrotoxicity. Although oxidative stress, mitochondrial dysfunction, and endoplasmic reticulum stress are implicated in the primary cytotoxic mechanisms, the secondary inflammatory pathways remain poorly understood. In this study, we aimed to elucidate the mechanisms underlying colistin-induced nephrotoxicity by analyzing the molecular responses of injured renal tubules isolated by laser microdissection (LMD) in a rat model. Six-week-old male Sprague-Dawley rats were subcutaneously administered colistin (0, 15, or 30 mg/kg/day) for 28 days. Increases in serum creatinine and blood urea nitrogen were associated with tubular vacuolation, single-cell necrosis, and regenerative changes in proximal tubules. Immunohistochemistry revealed increased expression of kidney injury molecule-1 (KIM-1) and presence of cleaved caspase-3 in the injured tubules, indicating epithelial regeneration and apoptosis, respectively. LMD-based microarray analysis identified 486 upregulated and 472 downregulated genes in vacuolated/regenerative tubules compared with normal tubules. Pathway analysis indicated activation of immune-related processes, particularly associated with macrophage activation and trafficking, including interleukin-34 (IL-34). In situ hybridization confirmed Il34 mRNA expression in the cytoplasm of the injured tubules, and accumulation of CD68-positive macrophages around KIM-1-positive tubules. Conversely, no significant change was observed in CD163-positive macrophages following colistin treatment, suggesting proinflammatory M1 macrophage predominance. These findings indicate that tubular IL-34 induction and subsequent macrophage recruitment amplify colistin-induced nephrotoxicity at the secondary level, suggesting that proximal tubules function as both primary targets and effectors of inflammation. Targeting the IL-34-related signaling could thus serve as a potential approach to alleviate colistin-induced renal injury.
Insights
Colistin antibiotic causes kidney damage through inflammation. Tubular cells release interleukin-34 (IL-34), attracting macrophages and worsening nephrotoxicity, suggesting IL-34 as a therapeutic target.
Area of Science:
- Nephrology
- Molecular Biology
- Immunology
Background:
- Colistin is vital against multidrug-resistant Gram-negative bacteria.
- Colistin's clinical use is limited by nephrotoxicity.
- Secondary inflammatory pathways in colistin nephrotoxicity are poorly understood.
Purpose of the Study:
- To elucidate mechanisms of colistin-induced nephrotoxicity.
- To analyze molecular responses in injured renal tubules.
- To investigate the role of inflammation in colistin's kidney injury.
Main Methods:
- Used a rat model with Sprague-Dawley rats administered colistin.
- Isolated injured renal tubules using laser microdissection (LMD).
- Performed microarray analysis and immunohistochemistry for gene expression and protein markers (KIM-1, cleaved caspase-3, CD68, CD163).
Main Results:
- Colistin induced kidney injury markers (serum creatinine, BUN), tubular damage, and regeneration.
- LMD-microarray revealed significant gene expression changes, including upregulation of immune-related genes.
- Interleukin-34 (IL-34) was upregulated in injured tubules, correlating with M1 macrophage accumulation, suggesting a proinflammatory response.
Conclusions:
- Tubular IL-34 induction and macrophage recruitment amplify colistin-induced nephrotoxicity.
- Proximal tubules act as both primary targets and inflammatory effectors.
- Targeting IL-34 signaling may mitigate colistin-induced renal injury.
