Distant organ effects of acute kidney injury Hamid Rabb Professor & Vice-Chairman Department of Medicine Johns Hopkins University Baltimore, USA
Mortality with acute kidney injury- AKI With availability of dialysis, patients are dying with AKI, but from extra-renal complications
Distant organs effect of AKI Grams M & Rabb H. Kidney Int August 2011
High mortality associated with combined AKI and lung injury in the ICU High mortality of patients in ICU with native kidney AKI remains around 50%, and has a mortality rate of >80% if associated with ventilation associated lung injury (VALI)
Mechanisms of renal influence on mortality Abundance of epidemiological data Increasing data on pathophysiology of AKI However, Paucity of integrated organ system data Lack of mechanistic data e.g. Does AKI contribute to respiratory dysfunction-independent of volume overload?
Hypothesis Acute kidney injury leads to increased pulmonary vascular permeability, a hallmark of acute lung injury (ARDS)
Kidney Int 1999
Kidney Int 1999
Kidney Int 1999
Transporter hypothesis Pulmonary edema after renal IRI is, in part, due to abnormalities in salt and water clearance/transport
Epithelial Sodium Channels (ENaC) Sodium channels have a role in regulating the volume of liquid on airway surfaces. (N Engl J Med 341:156, 1999) Sodium transport in the distal nephron is mediated by ENaC
Na Channel 28 S rrna Kidney Int 2003
Kidney Int 2003
What is the molecular signature of AKI distant lung effects?
Mice with renal IRI had increase in BAL total protein at 36 h BAL Protein ( g ml) 1000 800 600 400 200 Sham IRI BNx * 0 6 Hours 36 Hours Am J Physiol 2007
16.0 8.0 1.0 Genes expression lungs from mice BNx with renal IRI or BNx 6 HOURS IRI BNx 36 HOURS IRI Placenta-specific 8 Histocompatibility 2, class II antigen Scavenger receptor class B, member 1 Chemokine orphan receptor 1 Serum amyloid A 3 Phospholipase A2 Chemokine (C-C motif) ligand 6 C-type lectin domain family 4 Interferon induced protein 6 TYRO protein kinase binding protein Interleukin 1 receptor, type II Transforming growth factor induced S100 calcium binding protein A4 CD52 antigen -8.0-16.0 Synuclein, alpha Tumor necrosis factor receptor 19 Interferon-induced protein 2 Septin 4 Prickle like 1 Endothelin 1 Am J Physiol 2007
Biological processes activated in the lung during ischemic AKI at 6 h GOID GO Name Changed Genes Measured Genes Genes in GO Changed Genes (%) Z Score 6955 Immune response 15 83 273 18.1 11.72 6954 Inflammatory response 14 57 178 24.6 10.50 7166 Cell surface receptor signaling 9 54 128 16.7 5.15 7186 G-protein coupled receptor signaling 9 70 1738 12.9 4.17 6935 Chemotaxis 7 33 103 21.2 8.46 6928 Cell motility 7 68 108 10.3 3.49 1558 Regulation of cell growth 6 50 75 12.0 2.27 50896 Response to stimulus 5 23 261 21.7 9.73 Am J Physiol 2007
Biological processes activated in the lung during ischemic AKI at 36 h Am J Physiol 2007 GOID GO Name Changed Genes Measured Genes Genes in GO Changed Genes (%) Z Score 6512 Ubiquitin cycle 23 180 338 12.8 2.61 6915 Apoptosis 16 142 265 11.3 2.94 7264 Small GTPase mediated signaling 14 120 220 11.7 2.43 122 Negative regulation of transcription 10 54 120 18.5 4.01 1558 Regulation of cell growth 9 50 75 18.0 3.50 7186 G-protein coupled receptor signaling 9 70 1738 12.9 3.05 7283 Spermatogenesis 9 59 164 15.3 2.80 45449 Regulation of transcription 9 71 165 12.7 2.21 7166 Cell surface receptor linked signaling 8 54 128 14.8 5.17 6954 Inflammatory response 8 56 178 14.3 2.13 7507 Heart development 7 44 89 15.9 2.67 16481 Negative regulation of transcription 6 51 83 11.8 3.06 7169 Transmembrane receptor PTK signaling 6 29 84 20.7 2.70 45786 Negative regulation of cell cycle 5 29 50 17.2 2.22
Figure 1 Two Nodes: TNFR and Caspase Am J Physiol 2009
TUNEL - DAPI A Increased lung TUNEL staining during ischemic AKI Sham IRI BNx B 6 TUNEL (cells/hpf) 4 2 * 0 Sham IRI BNx Am J Physiol 2009
A Increased caspase 3 positive cells and activity in AKI Sham IRI BNx B Active Caspase-3 (cells/hpf) 6 5 4 3 2 1 * 6 Hours 24 Hours D Caspase-3 Activity (RFU X 10 3 ) 300 250 200 150 100 50 * 6 Hours 24 Hours 0 Sham IRI BNx 0 Sham IRI BNx C Am J Physiol 2009
Lung endothelial cells are the primary apoptotic cell during AKI CD34 DAPI A B TUNEL C D CD 34 TUNEL - DAPI Am J Physiol 2009
Protection from lung protein leak and apoptosis during AKI by Z-VAD-FMK A 1000 B 800 BAL Protein ( g/ml) 800 600 400 200 0 Sham * IRI Control Z-VAD-FMK Caspase-3 Activity (IU/mg protein) 600 400 200 0 Sham * IRI Control Z-VAD-FMK Am J Physiol 2009
Experimental AKI leads to pulmonary changes 1. Kramer & Rabb, KI 1999 2. Rabb & Soleimani, KI 2003 3. Hassoun & Rabb, AJP 2007 4. Grigoryev, & Rabb, JASN 2008 5. Hoag & Rabb, AJP 2008 6. Dodd-O & Rabb, AJP 2009 7. Hassoun & Rabb, AJP 2009 8. Feltes & Rabb, Shock 2011 1. Deng & Star, Am J Resp Crit Care Med 2004 2. Nath, AJPath, 2005 3. Kim &Woo, Respiration 2006 4. Zarbock & Singbartl, JASN 2006 5. Awad & Okusa, KI 2009 6. Tracz & Nath, KI 2007 7. Hoke & Faubel, JASN 2007 8. Klein & Faubel, KI 2008 9. Awad & Okusa, KI 2009 10. Campanholle & Camara, Inflam Res 2010
AKI and Brain-clinical 1. Central nervous system changes, from decreased mental status to seizures, are one of the classic indications to begin dialysis during AKI. 2. Despite the well-known association of acute severe kidney dysfunction with neurological changes, the underlying mechanisms are poorly understood.
Experimental design C57BL/6 mice Renal ischemia Reperfusion Ischemic AKI 60m 24h End points Brain harvest Mouse brain Sagittal dissection Histology (H&E, IHC) Liu & Rabb, JASN 2008 Snap frozen (gene array; protein array)
Mice with AKI had increased pyknotic neuronal cells in brain hippocampus (CA1) Brain histology P<0.003 Fig. 1. Pyknotic neuronal cells were significantly increased in the brain hippocampus in mice with severe ischemic AKI at 24 h.
AKI leads to increased number of microglia in the hippocampus of the brain Microglia
Posaitive Pixel Count/field Posaitive Pixel Count/field Mice with AKI at 24h had increased glial fibriliary acidic protein (inflammatory marker) in astrocytes Sagittal Section A: Corpus Callosum B: Cerebral Cortex Sham Sham Sham B A B A AKI AKI AKI A: Corpus Callosum B: Cereb. Cortex GFAP in Corpus Callosum P<0.0007 110000 100000 *** 90000 80000 70000 60000 50000 40000 30000 20000 sham AKI 10000 0 Sham IR GFAP Cerebral Cortex, adjecent to Corpus Caloosum 75000 *** 50000 25000 P<0.0001 sham AKI 0 Sham IR
Functional endpoint behavioral test Open field testing An open field test evaluates locomotor activity, exploratory behaviors and anxiety. Novelty-induced activity was assessed over a 30-min period using the activity chambers lined with infrared photo beams. Data are presented as photo beams breaking times over each interval or over total duration.
Photo beams breaking Mice with AKI at 24 h had significantly reduced locomotor activity compared to sham animals that underwent laparotomy and renal pedicle dissection Time course Total activity A Open Field Activity B Open Field Activity Sham Nephrectomy Ischmia 45 Ischemia 60 Sham Nephrectomy Ischemina 45 Ischemia 60 350 300 200 180 160 * P<0.001 vs. sham 250 140 200 150 100 50 0 0 3 6 9 12 15 18 21 24 27 30 33 Time interval 120 100 80 60 40 20 0 sham * B.Nx 1 ** * * IR45 IR60
AKI increases albumin permeability into brain (Left) and loosens blood brain barrier endothelial cells contacts (Right) Evans blue dye ( g/g dry tissue) 10000 1000 100 Sham AKI ** * 10 Kidney Brain ASN abstract 2009
Does AKI reduce brain threshold for a second hit e.g. stroke?
Procedure of permanent middle cerebral artery occlusion (pmcao) SHAM pmcao
AKI exacerbates outcomes of subsequent ischemic Stroke A B C D ASN abstract 2009
CONCLUSIONS AKI results in important changes to distant organs todate best studied mechanistically in the lung, but also in other organs AKI causes brain genomic, molecular, cellular, inflammatory and functional changes. AKI lowers the injury threshold for ischemic stroke Further discovery and targeting AKI-distant organ communication pathways should help improve outcomes from AKI
Summary AKI/ARF has an average mortality of 50% in the ICU despite dialysis AKI can lead to molecular changes and organ dysfunction in lung, heart and brain Detailed studies of classic inflammatory and transport pathways, plus novel pathways identified by systems biology tools, can reveal novel therapeutic targets and biomarkers of organ cross talk in critically ill patients with AKI. Improved dialysis techniques will hopefully lessen the effects of AKI on distant organ dysfunction
Distant organs effect of AKI Kidney Int 2011