Loss of Par-1a/b Polarity Proteins Leads to Increased Susceptibility to Acute Kidney Injury in Mice Ananna Kazi

Student, Junior Year, Binghamton University

Frederick Kaskel, MD, PHD and Kimberly Reidy, MD, Pediatric

Nephrology, Children’s Hospital at Montefiore/

Albert Einstein College of Medicine

A Patient I Saw• 19 day old baby girl with heart defect

underwent heart surgery• Creatinine 0.4 to 1.0 mg/dL (Estimated

glomerular filtration rate 19) • Urine output decreased

– Swollen body

Acute Kidney Injury (AKI)• Sudden inability of kidneys to filter

waste product from blood. • 5% to 7% of all patients admitted to

general medical-surgical hospitals have AKI. (Mandelbaum, MD et al., 2012)

• 20 to 50% of patients in Intensive Care Units (ICUs) develop AKI. (Case et al., 2013)

• Children are at high risk of AKI. (Andreoli, MD, 2008)

Acute Kidney Injury (AKI)• Symptoms: o Decreased urine output leads to fluid

retention in the body causing swelling in legs, ankles or feet, shortness of breath or chest pain

o Accumulation of toxins causes drowsiness, fatigue, nausea, confusion, seizures, or coma in severe cases

• Complex electrolyte alterationso Hyperkalemiao Hypocalcemiao Hyperphosphatemia

Pathophysiology of AKI• Causes:

– Ischemia– Drugs

• Decreased glomerular filtration rate (GFR)o Increased creatinine and Blood Urea

Nitrogen (BUN)• Proximal tubules are affected

o High metabolic rate• Lower blood flow as with ischemia

–Lower level of oxygen» Low ATP

Effects of Sub-lethal Injury to Tubular Cells

Sharfuddin, A. A. & Molitoris, B. A. (2011) Pathophysiology of ischemic acute kidney injuryNat. Rev. Nephrol. doi:10.1038/nrneph.2011.16

Healthy Cells

Injured Cells

Cell Polarity and Polarity Proteins• Asymmetric expression of proteins in

different parts of cells o differences in cell shape, structure, and

function• Epithelial Cell Polarity

o Required for solute transportation in kidney

Partitioning Defective 1 • Par polarity protein family • Localizes to the basolateral aspect of cells.• Complete deletion of Par-1a/b (Par-1a-/-:Par-

1b-/-) leads to death early in fetal development of mice.

• Contributes to proximal tubular development in newborn mice

• Expressed in developing nephron• Decreased expression in adult nephron • Increased expression in tubular injury (cisplatin,

folic acid) in mice

Hypothesis• Par-1a/b are protective in the setting of

kidney injury.• To test this:

– Cisplatin injected in mice– light microscopy used to examine injury

Cisplatin Induced InjuryMouse at 5 weeks

3 Days after Injection

Par-1a-/-

Par-1b-/-

Controls

Sacrificed

Methods• Histology

o Hematoxylin and Eosin Stain

• Immunohistochemistryo Ki67

Mouse Anti-Ki67

Donkey Anti-Mouse

Modified Image from Wikipedia

Increased Tubular Injury in Par-1b Knockout Mice

Par-1b-/- Cisplatin Injected Control Non-injected Control

30 m

g/kg

20 m

g/kg

Dilated Proximal Tubules

Injury

Decreased Proliferation in Par-1b Knockout Mice

Par

-1b-

/-C

ispl

atin

Inje

cted

C

ontro

ls

Merge /HoechstLTLKi67

Conclusions• Par-1b polarity proteins contribute to

tubular epithelial response to injury.• Either decreased or delayed

proliferation may contribute to the increased tubular injury in Par-1b-/- mice.

References• Andreoli, S. P. (2009). Acute kidney injury in

children. Pediatric Nephrology (Berlin, Germany), 24(2), 253–263. doi:10.1007/s00467-008-1074-9

• James Case, Supriya Khan, Raeesa Khalid, and Akram Khan, “Epidemiology of Acute Kidney Injury in the Intensive Care Unit,” Critical Care Research and Practice, vol. 2013, Article ID 479730, 9 pages, 2013. doi:10.1155/2013/479730

• Mandelbaum, T., Scott, D. J., Lee, J., Mark, R. G., Malhotra, A., Waikar, S. S., … Talmor, D. (2011). Outcome of Critically ill Patients with Acute Kidney Injury using the AKIN Criteria. Critical Care Medicine, 39(12), 2659–2664. doi:10.1097/CCM.0b013e3182281f1b

• Molitoris, B. A., & Sharfuddin, A. A. (2011). Pathophysiology of ischemic acute kidney injury. Nature Reviews Nephrology, 7(4), 189+. Retrieved from http://go.galegroup.com.proxy.binghamton.edu/ps/i.do?id=GALE%7CA253446287&v=2.1&u=bingul&it=r&p=HRCA&sw=w&asid=b6d6782267fcd907c22c5b7acd497d78

Acknowledgements• APS STEP-UP Fellowship

• NIH NIDDK K08 5K08DK091507

• T32 DK007110

• Dr. Kaskel and Dr. Reidy

• Dr. Du, Dr. Pal, and Dr. Koral