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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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Assessing the effect of proximal tubule cell specific SSAT deficiency on the severity of renal I/R injury.Wt and PT-SSAT-Cko were subjected to Sham or I/R surgery. Animals (n = 8/experimental group) were sacrificed at timed intervals after treatment. a) Serum creatinine and BUN levels of sham operated and injured wt and PT-SSAT-Cko mice were compared following the protocol out lined in the Methods Section. Results are expressed as mean+/-SEM. A p<0.05 is considered significant. b) Kidney histology (Mag 200x) of sham operated and injured wt- and PT-SSAT-Cko- animals were compared. c) Kidney histology (Mag 100x) of injured wt- and PT-SSAT-Cko- animals was compared.
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pone-0110161-g002: Assessing the effect of proximal tubule cell specific SSAT deficiency on the severity of renal I/R injury.Wt and PT-SSAT-Cko were subjected to Sham or I/R surgery. Animals (n = 8/experimental group) were sacrificed at timed intervals after treatment. a) Serum creatinine and BUN levels of sham operated and injured wt and PT-SSAT-Cko mice were compared following the protocol out lined in the Methods Section. Results are expressed as mean+/-SEM. A p<0.05 is considered significant. b) Kidney histology (Mag 200x) of sham operated and injured wt- and PT-SSAT-Cko- animals were compared. c) Kidney histology (Mag 100x) of injured wt- and PT-SSAT-Cko- animals was compared.

Mentions: The role of proximal tubule cell specific synthesis of SSAT in I/R injury has not been previously addressed. The severity of I/R injury was compared in wt and PT-SSAT-Cko mice in order to specifically determine the role of increased expression of SSAT in proximal tubule epithelial cells in the mediation of tubular damage and kidney dysfunction. Serum creatinine and BUN levels in all injured animals were significantly elevated compared to sham-operated animals (Fig. 2a). However, at 24 and 48 hours post I/R injury the serum creatinine and BUN levels were significantly (p<0.05) lower in PT-SSAT-Cko compared to wt mice (Fig. 2a). Next, in order to confirm the results of the aforementioned functional studies, we examined the histology of kidneys in wt and PT-SSAT-Cko mice after sham operation or renal I/R injury. Examination of the superficial cortical (outer-cortex) and cortico-medullary (inner-cortex/outer-medulla) regions of the kidneys of sham-operated (non-ishemic) wt- and PT-SSAT-Cko mice did not reveal any histological abnormalities (Table 1; Fig. 2b). Comparison of the cortical histopathology of ischemic kidneys revealed that wt mice showed moderate tubular dilatation, interstitial edema, and cast formation, the PT-SSAT-Cko mice were protected against these changes and had reduced injury levels compared to their wt counterparts (Fig. 2b). Examination of the histology of corticomedullary region of animals subjected to I/R injury revealed that whereas wt animals have extensive tubular damage (e.g. severe tubular dilation and cast formation) the PT-SSAT-Cko mice display significant protection against structural damage (e.g. moderate levels of tubular dilatation, cast formation and inflammatory cell infiltration) relative to their wt littermates (Fig. 2b). In general the SSAT-deficient animals exhibited less extensive and less severe ischemic injury compared to wt animals (Table 1,Fig. 2c). Our results suggest that the severity of parenchymal damage is reduced in PT-SSAT-Cko animals. The reduction of the severity of kidney damage (i.e. renal histopathology) in PT-SSAT-Cko animals in addition to the data indicating that these animals have better preserved renal function (i.e. serum creatinine and BUN levels) indicates that proximal tubule specific ablation of SSAT gene protects the kidneys against I/R injury. By extension, these studies suggest that enhanced SSAT expression and the attendant increase in polyamine back-conversion in proximal tubular epithelial cells plays a maladaptive role in the injury process in the kidneys subjected to I/R.


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)

Assessing the effect of proximal tubule cell specific SSAT deficiency on the severity of renal I/R injury.Wt and PT-SSAT-Cko were subjected to Sham or I/R surgery. Animals (n = 8/experimental group) were sacrificed at timed intervals after treatment. a) Serum creatinine and BUN levels of sham operated and injured wt and PT-SSAT-Cko mice were compared following the protocol out lined in the Methods Section. Results are expressed as mean+/-SEM. A p<0.05 is considered significant. b) Kidney histology (Mag 200x) of sham operated and injured wt- and PT-SSAT-Cko- animals were compared. c) Kidney histology (Mag 100x) of injured wt- and PT-SSAT-Cko- animals was compared.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0110161-g002: Assessing the effect of proximal tubule cell specific SSAT deficiency on the severity of renal I/R injury.Wt and PT-SSAT-Cko were subjected to Sham or I/R surgery. Animals (n = 8/experimental group) were sacrificed at timed intervals after treatment. a) Serum creatinine and BUN levels of sham operated and injured wt and PT-SSAT-Cko mice were compared following the protocol out lined in the Methods Section. Results are expressed as mean+/-SEM. A p<0.05 is considered significant. b) Kidney histology (Mag 200x) of sham operated and injured wt- and PT-SSAT-Cko- animals were compared. c) Kidney histology (Mag 100x) of injured wt- and PT-SSAT-Cko- animals was compared.
Mentions: The role of proximal tubule cell specific synthesis of SSAT in I/R injury has not been previously addressed. The severity of I/R injury was compared in wt and PT-SSAT-Cko mice in order to specifically determine the role of increased expression of SSAT in proximal tubule epithelial cells in the mediation of tubular damage and kidney dysfunction. Serum creatinine and BUN levels in all injured animals were significantly elevated compared to sham-operated animals (Fig. 2a). However, at 24 and 48 hours post I/R injury the serum creatinine and BUN levels were significantly (p<0.05) lower in PT-SSAT-Cko compared to wt mice (Fig. 2a). Next, in order to confirm the results of the aforementioned functional studies, we examined the histology of kidneys in wt and PT-SSAT-Cko mice after sham operation or renal I/R injury. Examination of the superficial cortical (outer-cortex) and cortico-medullary (inner-cortex/outer-medulla) regions of the kidneys of sham-operated (non-ishemic) wt- and PT-SSAT-Cko mice did not reveal any histological abnormalities (Table 1; Fig. 2b). Comparison of the cortical histopathology of ischemic kidneys revealed that wt mice showed moderate tubular dilatation, interstitial edema, and cast formation, the PT-SSAT-Cko mice were protected against these changes and had reduced injury levels compared to their wt counterparts (Fig. 2b). Examination of the histology of corticomedullary region of animals subjected to I/R injury revealed that whereas wt animals have extensive tubular damage (e.g. severe tubular dilation and cast formation) the PT-SSAT-Cko mice display significant protection against structural damage (e.g. moderate levels of tubular dilatation, cast formation and inflammatory cell infiltration) relative to their wt littermates (Fig. 2b). In general the SSAT-deficient animals exhibited less extensive and less severe ischemic injury compared to wt animals (Table 1,Fig. 2c). Our results suggest that the severity of parenchymal damage is reduced in PT-SSAT-Cko animals. The reduction of the severity of kidney damage (i.e. renal histopathology) in PT-SSAT-Cko animals in addition to the data indicating that these animals have better preserved renal function (i.e. serum creatinine and BUN levels) indicates that proximal tubule specific ablation of SSAT gene protects the kidneys against I/R injury. By extension, these studies suggest that enhanced SSAT expression and the attendant increase in polyamine back-conversion in proximal tubular epithelial cells plays a maladaptive role in the injury process in the kidneys subjected to I/R.

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