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Specific deletion of glycogen synthase kinase-3β in the renal proximal tubule protects against acute nephrotoxic injury in mice.

Howard C, Tao S, Yang HC, Fogo AB, Woodgett JR, Harris RC, Rao R - Kidney Int. (2012)

Bottom Line: This confirmed that hastened repair in the knockout mice was not merely due to lower initial injury levels.Thus, inhibition of GSK3β prior to nephrotoxic insult protects from renal injury.Such treatment after acute kidney injury may accelerate repair and regeneration.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA.

ABSTRACT
Renal proximal tubular damage and repair are hallmarks of acute kidney injury. As glycogen synthase kinase-3β (GSK3β) is an important cellular regulator of survival and proliferation, we determined its role during injury and recovery of proximal tubules in a mercuric chloride-induced nephrotoxic model of acute kidney injury. Renal proximal tubule-specific GSK3β knockout mice exposed to mercuric chloride had improved survival and renal function compared to wild-type mice. Apoptosis, measured by TUNEL staining, Bax activation, and caspase 3 cleavage, was reduced in the knockout mice. The restoration of renal structure, function, and cell proliferation was also accelerated in the GSK3β knockout mice. This enhanced repair, evidenced by increased Ki-67 and BRDU staining, along with increased cyclin D1 and c-myc levels, was recapitulated by treatment of wild-type mice with the small-molecule GSK3 inhibitor TDZD-8 following injury. This confirmed that hastened repair in the knockout mice was not merely due to lower initial injury levels. Thus, inhibition of GSK3β prior to nephrotoxic insult protects from renal injury. Such treatment after acute kidney injury may accelerate repair and regeneration.

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Recovery is faster in GSK3 inhibitor treated mice compared to similarly injured, but vehicle treated miceWT mice were injected once with 6.3 mg/kg HgCl2. After 48h, mice with comparable levels of BUN were administered vehicle or GSK3 inhibitor, TDZD-8 (1mg/kg BWt on day 2 and 0.5mg/kg BWt on day 3. a) Blood urea nitrogen levels decreased at a faster rate in TDZD-8 treated mice. b) injury score shows reduced injury in TDZD-8 treated mice, *, P<0.01. **, P<0.001, n=12 /group c) Representative image of renal cortex of WT and TDZD-8 treated mice, 4 days after HgCl2 treatment (hematoxylin and eosin, x100 original magnification).
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Figure 7: Recovery is faster in GSK3 inhibitor treated mice compared to similarly injured, but vehicle treated miceWT mice were injected once with 6.3 mg/kg HgCl2. After 48h, mice with comparable levels of BUN were administered vehicle or GSK3 inhibitor, TDZD-8 (1mg/kg BWt on day 2 and 0.5mg/kg BWt on day 3. a) Blood urea nitrogen levels decreased at a faster rate in TDZD-8 treated mice. b) injury score shows reduced injury in TDZD-8 treated mice, *, P<0.01. **, P<0.001, n=12 /group c) Representative image of renal cortex of WT and TDZD-8 treated mice, 4 days after HgCl2 treatment (hematoxylin and eosin, x100 original magnification).

Mentions: To probe further the role of GSK3β in regeneration following AKI we tested the effect of TDZD-8, a small-molecule inhibitor of GSK337, 38. In this study, TDZD-8 treatment was carried out after onset of injury in WT mice. WT mice were first administered 6.3 mg /kg of HgCl2. On day 2 (48 hours after HgCl2), BUN levels were measured and mice with of approximately 82±2 mg/dl were separated into two groups. One group was administered vehicle and the other, TDZD-8 (1 and 0.5 mg/kg respectively on day 2 and 3 after HgCl2 treatment). In the TDZD-8 treated group, BUN levels decreased significantly compared to vehicle treated group (vehicle, 72±9 vs TDZD-8, 51±6 mg/dl on day 4, n=9 and vehicle, 51±8 vs TDZD-8, 30±7 mg/dl on day 6, n=6) (Fig 7a). TDZD-8 treated mice also showed 40% and 36% lower kidney injury scores compared to vehicle-treated mice on days 4 and 6, respectively (Fig 7b, 7c), indicating that inhibition of GSK3 accelerated regeneration. Further, protein levels of cyclin D1, c-myc and β-catenin were significantly higher on days 3 and 4 in the TDZD-8 treated compared to vehicle treated mice (Fig 8a). By day 4, the number of BrdU positive nuclei in TDZD-8 treated mice was almost double when compared to vehicle treated mice (Fig 8b and 8c). Similarly, Ki-67 staining was more than double in the TDZD-8 treated mice, compared to the vehicle treated mice on day 4 (Fig 8d and 8e). Sirius red staining, on tissue sections, 8 days after HgCl2 treatment revealed no significant change in fibrosis between the two groups at this time point (supplemental data).


Specific deletion of glycogen synthase kinase-3β in the renal proximal tubule protects against acute nephrotoxic injury in mice.

Howard C, Tao S, Yang HC, Fogo AB, Woodgett JR, Harris RC, Rao R - Kidney Int. (2012)

Recovery is faster in GSK3 inhibitor treated mice compared to similarly injured, but vehicle treated miceWT mice were injected once with 6.3 mg/kg HgCl2. After 48h, mice with comparable levels of BUN were administered vehicle or GSK3 inhibitor, TDZD-8 (1mg/kg BWt on day 2 and 0.5mg/kg BWt on day 3. a) Blood urea nitrogen levels decreased at a faster rate in TDZD-8 treated mice. b) injury score shows reduced injury in TDZD-8 treated mice, *, P<0.01. **, P<0.001, n=12 /group c) Representative image of renal cortex of WT and TDZD-8 treated mice, 4 days after HgCl2 treatment (hematoxylin and eosin, x100 original magnification).
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Figure 7: Recovery is faster in GSK3 inhibitor treated mice compared to similarly injured, but vehicle treated miceWT mice were injected once with 6.3 mg/kg HgCl2. After 48h, mice with comparable levels of BUN were administered vehicle or GSK3 inhibitor, TDZD-8 (1mg/kg BWt on day 2 and 0.5mg/kg BWt on day 3. a) Blood urea nitrogen levels decreased at a faster rate in TDZD-8 treated mice. b) injury score shows reduced injury in TDZD-8 treated mice, *, P<0.01. **, P<0.001, n=12 /group c) Representative image of renal cortex of WT and TDZD-8 treated mice, 4 days after HgCl2 treatment (hematoxylin and eosin, x100 original magnification).
Mentions: To probe further the role of GSK3β in regeneration following AKI we tested the effect of TDZD-8, a small-molecule inhibitor of GSK337, 38. In this study, TDZD-8 treatment was carried out after onset of injury in WT mice. WT mice were first administered 6.3 mg /kg of HgCl2. On day 2 (48 hours after HgCl2), BUN levels were measured and mice with of approximately 82±2 mg/dl were separated into two groups. One group was administered vehicle and the other, TDZD-8 (1 and 0.5 mg/kg respectively on day 2 and 3 after HgCl2 treatment). In the TDZD-8 treated group, BUN levels decreased significantly compared to vehicle treated group (vehicle, 72±9 vs TDZD-8, 51±6 mg/dl on day 4, n=9 and vehicle, 51±8 vs TDZD-8, 30±7 mg/dl on day 6, n=6) (Fig 7a). TDZD-8 treated mice also showed 40% and 36% lower kidney injury scores compared to vehicle-treated mice on days 4 and 6, respectively (Fig 7b, 7c), indicating that inhibition of GSK3 accelerated regeneration. Further, protein levels of cyclin D1, c-myc and β-catenin were significantly higher on days 3 and 4 in the TDZD-8 treated compared to vehicle treated mice (Fig 8a). By day 4, the number of BrdU positive nuclei in TDZD-8 treated mice was almost double when compared to vehicle treated mice (Fig 8b and 8c). Similarly, Ki-67 staining was more than double in the TDZD-8 treated mice, compared to the vehicle treated mice on day 4 (Fig 8d and 8e). Sirius red staining, on tissue sections, 8 days after HgCl2 treatment revealed no significant change in fibrosis between the two groups at this time point (supplemental data).

Bottom Line: This confirmed that hastened repair in the knockout mice was not merely due to lower initial injury levels.Thus, inhibition of GSK3β prior to nephrotoxic insult protects from renal injury.Such treatment after acute kidney injury may accelerate repair and regeneration.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA.

ABSTRACT
Renal proximal tubular damage and repair are hallmarks of acute kidney injury. As glycogen synthase kinase-3β (GSK3β) is an important cellular regulator of survival and proliferation, we determined its role during injury and recovery of proximal tubules in a mercuric chloride-induced nephrotoxic model of acute kidney injury. Renal proximal tubule-specific GSK3β knockout mice exposed to mercuric chloride had improved survival and renal function compared to wild-type mice. Apoptosis, measured by TUNEL staining, Bax activation, and caspase 3 cleavage, was reduced in the knockout mice. The restoration of renal structure, function, and cell proliferation was also accelerated in the GSK3β knockout mice. This enhanced repair, evidenced by increased Ki-67 and BRDU staining, along with increased cyclin D1 and c-myc levels, was recapitulated by treatment of wild-type mice with the small-molecule GSK3 inhibitor TDZD-8 following injury. This confirmed that hastened repair in the knockout mice was not merely due to lower initial injury levels. Thus, inhibition of GSK3β prior to nephrotoxic insult protects from renal injury. Such treatment after acute kidney injury may accelerate repair and regeneration.

Show MeSH
Related in: MedlinePlus