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Updated: Sep 27, 2026
Phenotypic Characterization of Macrophages from Rat Kidney by Flow Cytometry
Published on: October 18, 2016
Macrophage-induced rat mesangial cell expression of the 24p3-like protein alpha-2-microglobulin-related protein
Izabella Z A Pawluczyk1, Peter N Furness, Kevin P G Harris
1Department of Nephrology, Leicester General Hospital, Gwendolen Road, Leicester LE5 4PW, UK. iap l@le.ac.uk
Abstract:
During screening of a murine macrophage cDNA repertoire for factors potentially able to modulate glomerular cell responses to injury, we identified a gene coding for the murine protein 24p3 lipocalin. Immunostaining of normal rat kidney sections showed positive 24p3-like staining in distal tubules/collecting ducts and small muscular arteries. Although most glomeruli were negative, some did exhibit small numbers of positively stained cells. Cultured rat glomeruli and glomerular mesangial cells secreted the 24p3-like protein in response to macrophage-conditioned medium (MPCM) and the cytokine IL-1beta. MPCM derived from TGFbeta-pretreated macrophages enhanced mesangial cell 24p3 secretion. In contrast, addition of anti-IL-1beta neutralising antibody to MPCM or IL-1beta resulted in suppression of 24p3 secretion. Co-culture of mesangial cells with varying numbers of non-LPS-treated macrophages resulted in dose-dependent secretion of 24p3 into culture supernatants. Archival sections from polyvinyl alcohol-treated and cholesterol-fed rats showed positive glomerular staining for 24p3 in and around glomerular foam cells. Nucleotide sequencing of rat mesangial cell-derived 24p3 cDNA revealed it to be identical to rat alpha-2-microglobulin-related protein (alpha2microGRP), the rat homologue of murine 24p3. These data provide the first description of rat alpha2microGRP in the context of mesangial cell pathophysiology.
Insights
Researchers identified the 24p3 lipocalin gene in mice, finding its rat homolog, alpha-2-microglobulin-related protein (alpha2microGRP), in kidney cells. This protein is secreted by mesangial cells in response to inflammatory signals.
Area of Science:
- Nephrology
- Molecular Biology
- Immunology
Background:
- Glomerular injury involves complex cellular responses.
- Lipocalins are a class of proteins with diverse biological functions.
- Macrophage-derived factors can influence kidney cell behavior.
Purpose of the Study:
- To identify factors from murine macrophages that modulate glomerular cell responses to injury.
- To characterize the expression and regulation of the identified protein in the rat kidney.
Main Methods:
- Screening of a murine macrophage cDNA library.
- Immunohistochemical staining of rat kidney sections.
- In vitro culture of rat glomeruli and mesangial cells.
- Stimulation with macrophage-conditioned medium (MPCM) and cytokines (IL-1beta, TGFbeta).
- Nucleotide sequencing of rat 24p3-like cDNA.
Main Results:
- Murine 24p3 lipocalin homolog was identified.
- 24p3-like protein showed staining in rat distal tubules, collecting ducts, and arteries; some glomeruli also stained positive.
- Rat mesangial cells secreted 24p3-like protein in response to MPCM and IL-1beta.
- TGFbeta-pretreated MPCM enhanced secretion, while anti-IL-1beta antibody suppressed it.
- Glomerular 24p3 staining was observed in foam cells in pathological conditions.
- Rat mesangial cell-derived 24p3 cDNA is identical to rat alpha-2-microglobulin-related protein (alpha2microGRP).
Conclusions:
- Rat alpha2microGRP is expressed in the kidney and secreted by mesangial cells.
- Its secretion is regulated by inflammatory cytokines and macrophage-derived factors.
- Alpha2microGRP is implicated in glomerular pathophysiology, particularly in the context of foam cells.
