Endothelial Dysfunction and Albuminuria in

Sickle Cell Disease

Kenneth I. Ataga, MD

Professor of Medicine

Comprehensive Sickle Cell Program

University of North Carolina -

Chapel Hill

Conflicts of Interest

• NIH grants - UO1HL117659, R01

HL111659

• Research funding - Selexys

Pharmaceuticals, Pfizer, Prolong

Pharmaceuticals

• Clinical Advisory Board and/or

Consultant - Global Blood Therapeutics,

Selexys Pharmaceuticals

Overview

• Introduction

• Prevalence of albuminuria

• Pathophysiology of albuminuria

• Association of biomarkers of

endothelial function with

albuminuria

• Treatment implications

Introduction

• There are 4 basic types of proteinuria

Glomerular

Tubular

Overflow

Post-renal

• Standard urine dipstick assessment primarily detects

albumin and is insensitive to presence of non-albumin

proteins

• Normal rate of albumin excretion is < 20 mg/day

Normal albuminuria: < 30 mg/day

Moderately increased albuminuria: 30 – 300 mg/day

Severely increased albuminuria: > 300 mg/day

Prevalence of Albuminuria/Proteinuria in

Children with SCD Reference Number of

Patients

Mean or Median

Age/ Range

Type of Study Measurement Prevalence

Alvarez et al,

2006

120 4-20 years Retrospective Microalbuminuria 15.8%

Dharnidharka et

al, 1998

102 2-18 years Prospective

Microalbuminuria 26.5%

McBurney et al,

2002

142 21 months-20

years

Retrospective Microalbuminuria 19%

McKie et al, 2007 191 3-20 years Prospective Microalbuminuria 19.4%

McPherson Yee

et al, 2011

410 2-21 years Cross-sectional Microalbuminuria 20.7%

Aygun et al, 2011 23 2.5-14 years Prospective Microalbuminuria 17.4%

Iwalokun et al,

2012

103 10.4** years Cross-sectional Albuminuria 22.3%

Wigfall et al, 2000 442 2-21 years Prospective

Proteinuria

(urinalysis)

4.5%

Forrest et al,

2012

85 6-21 years Retrospective Proteinuria

(urinalysis)

N/A

Ataga KI et al, AJH, 2014

Prevalence of Albuminuria/Proteinuria in

Adults with SCD Reference Number

of

Patients

Mean or Median

Age/ Range

Type of Study Measurement Prevalence

Thompson et al, 2007 65 18-23 years Cross-sectional Albuminuria 26.2%

Bolarinwa et al, 2012 68 15-60 years Cross-sectional Albuminuria 50.0%

Laurin et al, 2013 149 18-71 years Retrospective Albuminuria 45.0%

Ataga et al, 2010 73 39* years Cross-sectional Albuminuria 53.4%

Guasch et al, 2006 300 19-76 years Cross-sectional Albuminuria 58%

Asnani et al, 2011 121 24.1-32.5 years Cross-sectional Albuminuria 33.6%

Falk et al, 1992 381 N/A (children and

adults)

Prospective Proteinuria

(urinalysis)

26%

Aleem, 2010 67 23.8 ± 7.2

years**

Cross-sectional Proteinuria

(24hr urine)

40.3%

De Castro et al, 2008 75 39.3 ± 11.7

years**

Retrospective Proteinuria

(urinalysis)

28%

Elmariah et al, 2014 542 18-84 years Cross-sectional Proteinuria

(urinalysis)

26%

Ataga KI et al, AJH, 2014

Correlation of Spot UACR and 24-Hour

Urine Protein – Ataga KI et al, PLoS One, 2016

0 200 400 600 800 1000

Spot Urine Albumin-Creatinine Ratio (mg/g creatinine)

0

500

1000

1500

2000

24-h

our

Uri

ne P

rote

in (

mg/2

4 h

ours

)

Regression95% Prediction Limits

ρ = 0.90; 95% CI: 0.75 – 0.95, p < 0.0001

0 200 400 600 800 1000

Spot Urine Albumin-Creatinine Ratio (mg/g creatinine)

0

250

500

750

1000

1250

Aliquot

Alb

um

in-C

reatinin

e R

atio (

mg/g

cre

atinin

e)

Regression95% Prediction Limits

ρ = 0.97 95% CI: 0.92 – 0.99, p < 0.0001

Pathophysiology

• Hyperfiltration (Thompson J et al, 2007;

Haymann JP et al, 2010; Aygun B et al, 2011; King L et

al, 2011)

• Glomerular hypertension (Falk et al, 1992)

Physiologically similar to that in rodents

following subtotal nephrectomy

• Oxidative stress (Nath KA et al, 2001 & 2005;

Roy S et al, 2013)

• Chronic treatment with opioid

analgesics (Weber et al, 2012)

Pathophysiology

• Endothelial dysfunction

Conflicting data on association of hemolysis

with albuminuria (Guasch A et al, 2006; Ataga KI et al,

2010; Becton et al, 2010; Maer-Redelsperger et al, 2010; Gurkan

et al, 2010; Day et al, 2012; Drawz et al, 2016)

Association of hemoglobinuria with progression

of CKD and albuminuria (Saraf et al, 2014)

Associations between APOL1 G1/G2 and HMOX1

variants with CKD in SCD (Saraf et al, 2015)

sFLT-1 (Ataga et al, 2010; Youssry et al, 2015)

Soluble VCAM-1 and sFLT-1 are Associated with

Degree of Albuminuria – Ataga et al, EJH, 2010

sFLT-1 is Associated with Plasma Marker of

Endothelial Dysfunction – Ataga et al, EJH, 2010

r = 0.42, p = 0.0003

Hypothesis

• Endothelial dysfunction is an important

contributor to the pathophysiology of

albuminuria in SCD

• Improvement in endothelial function will

albuminuria, improve renal function

and likely improve overall mortality

Brachial Artery Ultrasound

Flow-mediated dilation (FMD)

Albuminuria is Associated with Flow-

Mediated Dilation – Ataga KI et al, Plos One, 2016

0 5 10 15

Flow-Mediated Dilation

0

250

500

750

1000S

pot

Uri

ne A

lbum

in-C

reatinin

e R

atio (

mg/g

cre

atinin

e)

RegressionSpot Urine Albumin-Creatinine Ratio (mg/g creatinine)

ρ = -0.45; 95% CI: -0.72 – -0.04, p = 0.031

Albuminuria is Associated with

Flow Mediated Dilation • Odds of severely

albuminuria was by

24% (OR: 0.76; 95% CI:

0.57 – 1.01) for every

1% in FMD

• Odds of moderate

albuminuria was by

9% (OR: 0.91; 95% CI:

0.72 – 1.45) for every

1% in FMD

Normal Moderately Increased Severely Increased

Albuminuria (categorical)

0

5

10

15

Flo

w-M

edia

ted D

ilation

Correlation of UACR with Biological

Variables

Ataga KI et al, PLoS One, 2016

Correlation of UACR with

Biological Variables

• In multivariable analyses, only ET-1,

VEGF and sFLT-1 were significantly

associated with UACR:

ET-1 (estimate: 455.1 [SE: 198.3], p = 0.02)

VEGF (estimate: -1.1 [SE: 0.53], p = 0.04)

sFLT-1 (estimate: -1.14 [SE: 0.49], p=0.02)

Ataga KI et al, PLoS One, 2016

Correlation of Flow-Mediated Dilation

with Biological Variables

Ataga KI et al, PLoS One, 2016

Correlation of Flow-Mediated Dilation

with Biological Variables

• In multivariable analyses, only ET-1

was significantly associated with FMD

ET-1 (estimate: -8.03 [SE: 3.87], p = 0.04)

Ataga KI et al, PLoS One, 2016

Treatment Implications

• Few treatment studies of

albuminuria in SCD

• ACE inhibitors are “standard of

care”

• No large, long-term treatment

studies

• Hydroxyurea may be beneficial

Effect of ETA Receptor Antagonist on ROS,

Protein and Nephrin Excretion

Heimlich JB et al, Br J Pharmacol, 2016

Experimental Design

SS/AA mice

8 weeks, Atorvastatin, po 10mg/kg/day, n=10

(Lipitor)

RT3

Humanized Knock-in Sickle mouse (Townes)

Courtesy of David Archer, PhD (Unpublished)

Baseline Characteristics

GFR

(ul/min)

Urine

Osmolality

AER

(ug/day)

Hct Retic

(%)

AA 132 ±

5.9

2854 ± 125 96.9 ±8.8 31.8 ±0.4 5.3 ±0.3

SS vehicle 95.2±

2.6

2077± 50 148 ± 14.8 28.3 ±1.0 38.5 ±

1.6

SS Statin 88.0±

2.6

2078 ± 51 151.4±

15.2

26.4 ±0.5 43.3±

2.1

Urinary Biomarkers

AA SS SS Statin0

5

10

15

Ne

ph

rin

(n

g/d

ay

)

p <0.05

AA SS SS Statin0

1000

2000

3000

KIM

1 (

pg

/da

y

p<0.05A B C

AA SS SS Statin0

50

100

150

200

250

NG

AL

(n

g/d

ay

)

Renal Function

AA SS SS Statin0

50

100

150

200

250

Alb

(u

g/d

ay

)

p<0.05

AA SS SS Statin0

50

100

150

200

250

300

350

Uri

ne

Alb

/Cr

(ug

/mg

) p<0.05

A B C

AA SS SS Statin0

1

2

3

4

5

Uri

ne

Vo

lum

e (

ml)

p<0.05p<0.05

Ongoing Clinical Studies of Interest

• Effect of atorvastatin on endothelial

function and albuminuria in sickle cell

disease (UNC – Chapel Hill)

• The role of endothelin-1 in sickle cell

disease (Augusta University)

• A multi-center study of riociguat in

patients with sickle cell disease

(University of Pittsburgh)

Summary

• Albuminuria/CKD is a common complication in SCD

• Pathophysiology likely due to glomerular HTN, hyperfiltration, oxidative stress and endothelial dysfunction

• Commonly treated with ACE inhibitors and ARBs hydroxyurea

• Novel treatments are needed for the glomerulopathy of SCD

Acknowledgement

UNC at Chapel Hill

• Melissa Caughey, PhD

• Poulami Maitra, MS

• Jianwen Cai, PhD

• Laila Elsherif, PhD

• Jessica Shen, BS

• Susan K Jones, RN

• Vimal Derebail, MD

• Alan Hinderliter, MD

Emory University & UAB

• David R. Archer, PhD

• David M. Pollock, PhD