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Proximal tubule epithelial cell specific ablation of the spermidine/spermine N1-acetyltransferase gene reduces the severity of renal ischemia/reperfusion injury.

Zahedi K, Barone S, Wang Y, Murray-Stewart T, Roy-Chaudhury P, Smith RD, Casero RA, Soleimani M - PLoS ONE (2014)

Bottom Line: Severity of the loss of kidney function and tubular damage are reduced in PT-SSAT-Cko- compared to wt-mice after I/R injury.Finally, the activation of caspase3 was more pronounced in the wt compared to PT-SSAT-Cko animals.Enhanced SSAT expression by proximal tubule epithelial cells leads to tubular damage, and its deficiency reduces the severity of renal I/R injury through reduction of cellular damage and modulation of the innate immune response.

View Article: PubMed Central - PubMed

Affiliation: Division of Nephrology and Hypertension, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America; Veterans Affair Medical Center, Cincinnati, Ohio, United States of America.

ABSTRACT

Background: Expression and activity of spermidine/spermine N1-acetyltransferase (SSAT) increases in kidneys subjected to ischemia/reperfusion (I/R) injury, while its ablation reduces the severity of such injuries. These results suggest that increased SSAT levels contribute to organ injury; however, the role of SSAT specifically expressed in proximal tubule epithelial cells, which are the primary targets of I/R injury, in the mediation of renal damage remains unresolved.

Methods: Severity of I/R injury in wt and renal proximal tubule specific SSAT-ko mice (PT-SSAT-Cko) subjected to bilateral renal I/R injury was assessed using cellular and molecular biological approaches.

Results: Severity of the loss of kidney function and tubular damage are reduced in PT-SSAT-Cko- compared to wt-mice after I/R injury. In addition, animals treated with MDL72527, an inhibitor of polyamine oxidases, had less severe renal damage than their vehicle treated counter-parts. The renal expression of HMGB 1 and Toll like receptors (TLR) 2 and 4 were also reduced in PT-SSAT-Cko- compared to wt mice after I/R injury. Furthermore, infiltration of neutrophils, as well as expression of tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1) and interleukin-6 (IL-6) transcripts were lower in the kidneys of PT-SSAT-Cko compared to wt mice after I/R injury. Finally, the activation of caspase3 was more pronounced in the wt compared to PT-SSAT-Cko animals.

Conclusions: Enhanced SSAT expression by proximal tubule epithelial cells leads to tubular damage, and its deficiency reduces the severity of renal I/R injury through reduction of cellular damage and modulation of the innate immune response.

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Proximal Tubule Epithelial Cell (PTEC) specific ablation of the SSAT gene dampens the onset of innate immune response and reduces the extent of I/R induced apoptotic cell death.The onset of innate immune response after I/R injury was compared in wt and PT-SSAT-Cko animals. a) Time course of the expression of HMGB1, TLR2 and 4 were compared in the kidneys of sham-operated and injured wt and PT-SSAT-Cko mice. The data are representative of three independent experiments. b) Expression of TLR2 and 4 were assessed by immunofluorescent microscopic examination of kidneys of wt and PT-SSAT-Cko mice after sham- or I/R surgery.
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pone-0110161-g007: Proximal Tubule Epithelial Cell (PTEC) specific ablation of the SSAT gene dampens the onset of innate immune response and reduces the extent of I/R induced apoptotic cell death.The onset of innate immune response after I/R injury was compared in wt and PT-SSAT-Cko animals. a) Time course of the expression of HMGB1, TLR2 and 4 were compared in the kidneys of sham-operated and injured wt and PT-SSAT-Cko mice. The data are representative of three independent experiments. b) Expression of TLR2 and 4 were assessed by immunofluorescent microscopic examination of kidneys of wt and PT-SSAT-Cko mice after sham- or I/R surgery.

Mentions: HMGB1 binding to TLR2 and 4 and activation of the innate immune response can lead to inflammation and apoptosis and play an important role in the mediation of renal I/R injury [22]–[26]. Based on increased expression of HMGB1 in SSAT expressing cells (Fig. 6b), and our in vivo results showing a reduction in leukocyte infiltration in PT-SSAT-Cko compared to wt animals (Table 1; Fig. 2b and c) we postulated that the lack of SSAT and reduced cell injury can modulate the onset of innate immunity and further reduce the severity of renal injury in PT-SSAT-Cko animals. In order to test this, we compared the onset of innate immune response (e.g. expression levels of HMGB1, TLR2 and TLR4) and apoptosis (cleaved caspase 3 levels) after I/R injury in wt and PT-SSAT-Cko mice. Although the renal expression of HMGB1, TLR2 and TLR4 increase in response to I/R injury in both groups, the expression of these molecules are reduced in PT-SSAT-Cko- compared to wt-animals (Fig. 7 a and b). The differences in the activation of innate immune response were further examined by comparing the extent of neutrophil infiltration and pro-inflammatory cytokine expression in the kidneys of wt and PT-SSAT-Cko animals after I/R injury. Examination of TNF-α, MCP-1 and IL-6 transcripts in the kidneys of injured animals revealed that the expression levels of these cytokines are reduced in PT-SSAT-Cko- compared to wt-mice after I/R injury (Fig. 8a). Assessment of the protein levels of the aforementioned cytokines also revealed that although the renal content of these cytokines is elevated in both wt- and PT-SSAT-Cko-mice, the former have a more robust response (Fig. 8b). Specifically, while the levels of all cytokines increased significantly in injured compared to control kidneys (sham operated animals) at 24 and 48 hours, the cytokine levels in the kidneys of wt animals compared to their PT-SSAT-Cko animals were significantly higher at 48 hrs post I/R injury (Fig. 8b). Additionally, chloroacetate esterase staining of the kidney sections revealed that compared to wt-mice the PT-SSAT-Cko animals have reduced levels of neutrophil infiltration (Fig. 8c).


Proximal tubule epithelial cell specific ablation of the spermidine/spermine N1-acetyltransferase gene reduces the severity of renal ischemia/reperfusion injury.

Zahedi K, Barone S, Wang Y, Murray-Stewart T, Roy-Chaudhury P, Smith RD, Casero RA, Soleimani M - PLoS ONE (2014)

Proximal Tubule Epithelial Cell (PTEC) specific ablation of the SSAT gene dampens the onset of innate immune response and reduces the extent of I/R induced apoptotic cell death.The onset of innate immune response after I/R injury was compared in wt and PT-SSAT-Cko animals. a) Time course of the expression of HMGB1, TLR2 and 4 were compared in the kidneys of sham-operated and injured wt and PT-SSAT-Cko mice. The data are representative of three independent experiments. b) Expression of TLR2 and 4 were assessed by immunofluorescent microscopic examination of kidneys of wt and PT-SSAT-Cko mice after sham- or I/R surgery.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4229091&req=5

pone-0110161-g007: Proximal Tubule Epithelial Cell (PTEC) specific ablation of the SSAT gene dampens the onset of innate immune response and reduces the extent of I/R induced apoptotic cell death.The onset of innate immune response after I/R injury was compared in wt and PT-SSAT-Cko animals. a) Time course of the expression of HMGB1, TLR2 and 4 were compared in the kidneys of sham-operated and injured wt and PT-SSAT-Cko mice. The data are representative of three independent experiments. b) Expression of TLR2 and 4 were assessed by immunofluorescent microscopic examination of kidneys of wt and PT-SSAT-Cko mice after sham- or I/R surgery.
Mentions: HMGB1 binding to TLR2 and 4 and activation of the innate immune response can lead to inflammation and apoptosis and play an important role in the mediation of renal I/R injury [22]–[26]. Based on increased expression of HMGB1 in SSAT expressing cells (Fig. 6b), and our in vivo results showing a reduction in leukocyte infiltration in PT-SSAT-Cko compared to wt animals (Table 1; Fig. 2b and c) we postulated that the lack of SSAT and reduced cell injury can modulate the onset of innate immunity and further reduce the severity of renal injury in PT-SSAT-Cko animals. In order to test this, we compared the onset of innate immune response (e.g. expression levels of HMGB1, TLR2 and TLR4) and apoptosis (cleaved caspase 3 levels) after I/R injury in wt and PT-SSAT-Cko mice. Although the renal expression of HMGB1, TLR2 and TLR4 increase in response to I/R injury in both groups, the expression of these molecules are reduced in PT-SSAT-Cko- compared to wt-animals (Fig. 7 a and b). The differences in the activation of innate immune response were further examined by comparing the extent of neutrophil infiltration and pro-inflammatory cytokine expression in the kidneys of wt and PT-SSAT-Cko animals after I/R injury. Examination of TNF-α, MCP-1 and IL-6 transcripts in the kidneys of injured animals revealed that the expression levels of these cytokines are reduced in PT-SSAT-Cko- compared to wt-mice after I/R injury (Fig. 8a). Assessment of the protein levels of the aforementioned cytokines also revealed that although the renal content of these cytokines is elevated in both wt- and PT-SSAT-Cko-mice, the former have a more robust response (Fig. 8b). Specifically, while the levels of all cytokines increased significantly in injured compared to control kidneys (sham operated animals) at 24 and 48 hours, the cytokine levels in the kidneys of wt animals compared to their PT-SSAT-Cko animals were significantly higher at 48 hrs post I/R injury (Fig. 8b). Additionally, chloroacetate esterase staining of the kidney sections revealed that compared to wt-mice the PT-SSAT-Cko animals have reduced levels of neutrophil infiltration (Fig. 8c).

Bottom Line: Severity of the loss of kidney function and tubular damage are reduced in PT-SSAT-Cko- compared to wt-mice after I/R injury.Finally, the activation of caspase3 was more pronounced in the wt compared to PT-SSAT-Cko animals.Enhanced SSAT expression by proximal tubule epithelial cells leads to tubular damage, and its deficiency reduces the severity of renal I/R injury through reduction of cellular damage and modulation of the innate immune response.

View Article: PubMed Central - PubMed

Affiliation: Division of Nephrology and Hypertension, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America; Veterans Affair Medical Center, Cincinnati, Ohio, United States of America.

ABSTRACT

Background: Expression and activity of spermidine/spermine N1-acetyltransferase (SSAT) increases in kidneys subjected to ischemia/reperfusion (I/R) injury, while its ablation reduces the severity of such injuries. These results suggest that increased SSAT levels contribute to organ injury; however, the role of SSAT specifically expressed in proximal tubule epithelial cells, which are the primary targets of I/R injury, in the mediation of renal damage remains unresolved.

Methods: Severity of I/R injury in wt and renal proximal tubule specific SSAT-ko mice (PT-SSAT-Cko) subjected to bilateral renal I/R injury was assessed using cellular and molecular biological approaches.

Results: Severity of the loss of kidney function and tubular damage are reduced in PT-SSAT-Cko- compared to wt-mice after I/R injury. In addition, animals treated with MDL72527, an inhibitor of polyamine oxidases, had less severe renal damage than their vehicle treated counter-parts. The renal expression of HMGB 1 and Toll like receptors (TLR) 2 and 4 were also reduced in PT-SSAT-Cko- compared to wt mice after I/R injury. Furthermore, infiltration of neutrophils, as well as expression of tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1) and interleukin-6 (IL-6) transcripts were lower in the kidneys of PT-SSAT-Cko compared to wt mice after I/R injury. Finally, the activation of caspase3 was more pronounced in the wt compared to PT-SSAT-Cko animals.

Conclusions: Enhanced SSAT expression by proximal tubule epithelial cells leads to tubular damage, and its deficiency reduces the severity of renal I/R injury through reduction of cellular damage and modulation of the innate immune response.

Show MeSH
Related in: MedlinePlus