AKAP150 Contributes to Enhanced Vascular Tone by Facilitating Large-Conductance Ca ²⁺ -Activated K ⁺ Channel Remodeling in Hyperglycemia and Diabetes Mellitus

Q: What are the key findings of this study?

Genetic ablation of AKAP150 or disruption of AKAP150-calcineurin anchoring prevented BKCa β1 subunit downregulation and attenuated high-fat diet-induced blood pressure increases by ~60% and ~40%, respectively.

Q: What is the clinical evidence from this study?

Population: Hyperglycemia and type 2 diabetes mellitus (high-fat diet mouse model). Intervention: Genetic ablation of AKAP150 (AKAP150-/-) or disruption of AKAP150-calcineurin anchoring (ΔPIX knock-in) and high-fat diet / hyperglycemic exposure vs. Wild-type mice on low-fat control diet (10% kcal) in vivo; 5 or 10 mmol/L D-glucose ex vivo. Primary outcome: Vascular tone, BKCa channel function (open probability and β1 subunit expression), and mean arterial blood pressure (p=<0.05).

Q: What does this research mean for the field?

Subcellular anchoring of calcineurin by AKAP150 mediates BKCa channel β1 subunit downregulation, promoting enhanced arterial constriction and elevated blood pressure in hyperglycemia and diabetes mellitus. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.NEUTRAL.

Q: What question did this study set out to answer?

To determine whether AKAP150-dependent calcineurin signaling drives the downregulation of BKCa channel β1 subunits and impairs vascular function during hyperglycemia and diabetes.

Matthew A. Nystoriak; Madeline Nieves‐Cintrón; Patrick J. Nygren; Simon A. Hinke; C. Blake Nichols; Chao-Yin Chen; Jośe L. Puglisi; Leighton T. Izu; Donald M. Bers; Mark L. Dell’Acqua; John D. Scott; Luis F. Santana; Manuel F. Navedo

doi:10.1161/circresaha.114.302168

December 10, 2013Circulation ResearchOpen Access

AKAP150 Contributes to Enhanced Vascular Tone by Facilitating Large-Conductance Ca ²⁺ -Activated K ⁺ Channel Remodeling in Hyperglycemia and Diabetes Mellitus

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Key result

AKAP150 disruption blunts diet-induced blood pressure elevation by up to ~60% in preclinical models.

P<0.05

Why the study?

Does AKAP150-dependent calcineurin/NFATc3 signaling mediate BKCa β1 subunit downregulation, enhanced vascular tone, and elevated arterial blood pressure during hyperglycemia and high-fat diet-induced diabetes mellitus in mice?

Key Points

To determine whether AKAP150-dependent calcineurin signaling drives the downregulation of BKCa channel β1 subunits and impairs vascular function during hyperglycemia and diabetes.
Studied isolated arteries and arterial myocytes from wild-type, AKAP150-null (AKAP150-/-), and calcineurin-binding mutant mice fed either a low-fat or high-fat diet.
Measured arterial tone at 60 mmHg intravascular pressure, single-channel BKCa currents via patch clamp, and Ca2+ sparks via spinning disk confocal microscopy.
Tested isolated arteries exposed ex vivo to 5, 10, or 20 mmol/L D-glucose with or without L-type Ca2+ channel blockers or the calcineurin inhibitor cyclosporine A.
Arteries from wild-type high-fat diet mice displayed elevated vascular tone compared to low-fat controls (29 ± 4% vs 17 ± 2%) and blunted iberiotoxin constriction (2 ± 2% vs 13 ± 4% diameter decrease), but these changes were absent in AKAP150-/- mice.
Wild-type mice on a high-fat diet showed an approximate 65% loss of BKCa β1 subunit protein and reduced channel open probability, without changes in pore-forming α subunits or Ca2+ spark frequency.
Incubating wild-type arteries in 20 mmol/L D-glucose caused a >50% reduction in β1 transcript and protein expression, which was prevented by nifedipine, cyclosporine A, or AKAP150 ablation.

Structured PICO

Does AKAP150-dependent calcineurin/NFATc3 signaling mediate BKCa β1 subunit downregulation, enhanced vascular tone, and elevated arterial blood pressure during hyperglycemia and high-fat diet-induced diabetes mellitus in mice?

P

Population

Preclinical mouse models (WT, AKAP150-/-, NFATc3-/-, and ΔPIX knock-in mice) fed a high-fat diet (60% kcal) or low-fat control diet (10% kcal) for 24-26 weeks starting at 5 weeks of age, along with ex vivo organ-cultured cerebral and mesenteric arteries incubated in D-glucose for 48 hours.

I

Intervention

Genetic ablation of AKAP150 (AKAP150-/-) or selective perturbation of AKAP150-calcineurin interaction (ΔPIX knock-in), challenged with a high-fat diet (60% kcal) for 24-26 weeks in vivo or hyperglycemic culture media (20 mmol/L D-glucose) for 48 hours ex vivo (with pharmacological testing using iberiotoxin 100 nmol/L, tamoxifen 1 μmol/L, nifedipine 1 μmol/L, diltiazem 50 μmol/L, or cyclosporine A 1 μmol/L).

C

Comparator

Age-matched wild-type (WT) mice fed a low-fat control diet (10% kcal) or high-fat diet (60% kcal) in vivo, or arteries incubated in normoglycemic media (5 or 10 mmol/L D-glucose, 15 mmol/L mannitol, or 15 mmol/L L-glucose) ex vivo.

O

Outcome

Vascular BKCa channel remodeling (β1 and α subunit protein/transcript expression and single-channel open probability Po), calcineurin/NFATc3 activation (nuclear translocation and Ser265 dephosphorylation), resistance artery constriction/vascular tone (at 60 mmHg), and telemetric mean arterial blood pressure.surrogate

Main Result

p-value: p=<0.05

Identifies subcellular anchoring of calcineurin by AKAP150 as an essential molecular mechanism driving vascular BKCa channel remodeling, vasoconstriction, and hypertension in a preclinical model of type 2 diabetes, suggesting selective targeting of the AKAP150-calcineurin interaction as a potential therapeutic strategy.

Limitations

Preclinical animal and ex vivo study; findings may not directly translate to human diabetic patients
Changes in cardiac output in high-fat diet animals were not assessed by echocardiography and may also participate in modulation of blood pressure
Changes in BKCa channel function in cerebral arteries have a limited impact on systemic blood pressure compared to mesenteric arteries
Post-translational modifications such as phosphorylation and oxidation were not tested in this experimental type 2 diabetes model
Preclinical animal and cellular study without human clinical testing
Potential changes in cardiac output in high-fat diet mice were not evaluated with echocardiography
Cerebral artery BKCa channel changes have limited impact on systemic blood pressure compared to mesenteric arteries
Role of post-translational modifications (e.g., oxidation, ubiquitin ligase-dependent degradation) was not evaluated in this model

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Implication

AKAP150-calcineurin disruption may mitigate diabetic hypertension in mice; leaves open translation to human therapy.

Abstract

RATIONALE: Increased contractility of arterial myocytes and enhanced vascular tone during hyperglycemia and diabetes mellitus may arise from impaired large-conductance Ca(2+)-activated K(+) (BKCa) channel function. The scaffolding protein A-kinase anchoring protein 150 (AKAP150) is a key regulator of calcineurin (CaN), a phosphatase known to modulate the expression of the regulatory BKCa β1 subunit. Whether AKAP150 mediates BKCa channel suppression during hyperglycemia and diabetes mellitus is unknown. OBJECTIVE: To test the hypothesis that AKAP150-dependent CaN signaling mediates BKCa β1 downregulation and impaired vascular BKCa channel function during hyperglycemia and diabetes mellitus. METHODS AND RESULTS: We found that AKAP150 is an important determinant of BKCa channel remodeling, CaN/nuclear factor of activated T-cells c3 (NFATc3) activation, and resistance artery constriction in hyperglycemic animals on high-fat diet. Genetic ablation of AKAP150 protected against these alterations, including augmented vasoconstriction. d-glucose-dependent suppression of BKCa channel β1 subunits required Ca(2+) influx via voltage-gated L-type Ca(2+) channels and mobilization of a CaN/NFATc3 signaling pathway. Remarkably, high-fat diet mice expressing a mutant AKAP150 unable to anchor CaN resisted activation of NFATc3 and downregulation of BKCa β1 subunits and attenuated high-fat diet-induced elevation in arterial blood pressure. CONCLUSIONS: Our results support a model whereby subcellular anchoring of CaN by AKAP150 is a key molecular determinant of vascular BKCa channel remodeling, which contributes to vasoconstriction during diabetes mellitus.

Discussion

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Cite This Study

Nystoriak et al. (2013) studied Hyperglycemia and type 2 diabetes mellitus (high-fat diet mouse model). Genetic ablation of AKAP150 (AKAP150-/-) or disruption of AKAP150-calcineurin anchoring (ΔPIX knock-in) and high-fat diet / hyperglycemic exposure vs. Wild-type mice on low-fat control diet (10% kcal) in vivo; 5 or 10 mmol/L D-glucose ex vivo was evaluated on Vascular tone, BKCa channel function (open probability and β1 subunit expression), and mean arterial blood pressure (p=<0.05). Genetic ablation of AKAP150 or disruption of AKAP150-calcineurin anchoring prevented BKCa β1 subunit downregulation and attenuated high-fat diet-induced blood pressure increases by ~60% and ~40%, respectively.

synapsesocial.com/papers/6a733e8e03bfdad20fc67477 https://doi.org/10.1161/circresaha.114.302168

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AKAP150 Contributes to Enhanced Vascular Tone by Facilitating Large-Conductance Ca ²⁺ -Activated K ⁺ Channel Remodeling in Hyperglycemia and Diabetes Mellitus

Key Points

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

AKAP150 Contributes to Enhanced Vascular Tone by Facilitating Large-Conductance Ca ²⁺ -Activated K ⁺ Channel Remodeling in Hyperglycemia and Diabetes Mellitus

Key Points

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

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