Pathophysiology in AKI

1. Acute Kidney injury
Pathophysiology
and Novel biomarker
CHAKEN MANIYAN M.D.
Nephrology fellow ,
Phramongkutklao hospital
19 Aug 2016

2. Scope : Part I
• Pathophysiology
• Pre-renal AKI
• Post-renal AKI
• Renal (focus on acute tubular necrosis) AKI
• Hemodynamic / endothelium injury
• Inflammatory response
• Tubular injury
• Cell death and regeneration

3. Pathophysiology of prerenal AKI
A physiologic response to mild-moderate renal hypoperfusion
Rapid reversible upon restoration of RBF and glomerular
filtration pressure
More severe hypoperfusion lead to ischemic injury and
intrinsic renal AKI
Thus, prerenal AKI and intrinsic renal AKI due to ischemia are
part of a spectrum of manifestations of renal hypoperfusion.

4. Compensatory mechanisms
A physiologic response to mild-moderate renal hypoperfusion
EXTRINSIC:
Neurohormonal mechanisms
Pituitary response
INTRINSIC:
RAAS activation
Tubuloglomerular feedback
Afferent arteriolar dilatation
Efferent arteriolar constriction

5. Homeostasis to maintain RBF
Critical Care Medicine: Principles of Diagnosis and Management in the Adult .4th edition
RAAS
activation

6. Regulation of renal perfusion pressure
J. Gary Abuelo,N Engl J Med 2007; 357:797-805

7. Pathophysiology of Post renal AKI

8. Obstruction can affect
hemodynamic variables and GFR
GFR = Kf x (PGC-PT- ΠGC)
Kf - glomerular ultrafiltration coeffecient (related to surface area and
permeability of capillary membrane)
PGC- glomerular capillary pressure (influenced by RBF and resistance of
afferent and efferent arterioles)
PT - hydraulic pressure of fluid in tubule
ΠGC- oncotic pressure of proteins in glomerular capillary
RBF = (aortic pressure - renal venous pressure)
renal vascular resistance
Influences PGC constriction of afferent arteriole will result in a decrease of
PGC and GFR
An increase in efferent arteriolar resistance will increase PGC
Campbell-Walsh Urology, 11th Edition, 2016 Elsevier Inc.

9. Summary of renal hemodynamic change UUO and BUO
Campbell-Walsh Urology, 11th Edition, 2016 Elsevier Inc.

10. Triphasic pattern of UUO
Smith's Textbook of endourology 3rd edition vol I
Pre-glomerular
vasodilatation
Post-glomerular
vasoconstriction
Pre and Post-glomerular
vasoconstriction

11. Regulation of GFR in Response to Obstruction
• After release of obstruction
• RBF is increased
• GFR remains low because of nonperfusion or
underperfusion of many glomeruli
• Intense afferent vasoconstriction reduces PGC, so that
even though PT also falls with release of the obstruction
• Macula densa likely senses dramatic change in rate of
flow, and this may lead to intense vasoconstriction
Nevo A, et al. Urology. 2014 Dec. 84 (6):1475-9

12. Recovery of Glomerular Function
after Relief of Obstruction
• Depends on several factors,
• Duration and extent of obstruction
• Presence of functioning contralateral kidney
• Presence of associated infection
• Level of pre obstruction RBF
Nevo A, et al. Urology. 2014 Dec. 84 (6):1475-9

13. Pathophysiology of ATN

14. Morphologic changes
• Classical hallmark of ATN is loss of apical
brush border of proximal tubular cell
• Detached tubular cell , denuded tubular
basement and focal proximal tubular dilatation
• Sloughed tubule cells, brush border vesicle
remnants, and cellular debris in combination
with Tamm-Horsfall protein form classical
muddy-brown granular casts
J Am Soc Nephrol. 2011 Mar;22(3):416-25

15. Major biochemical change
• Intracellular calcium accumulation
• ROS
• Activation of phospholipases and proteases
• ATP depletion
• The net effect result in
• Cell death
• Sloughing of viable cells into tubule lumen by impairment of
normal cell-to-basement membrane adhesion
• Activation of inflammatory response
J Am Soc Nephrol. 2011 Mar;22(3):416-25

16. Destiny of injury
Insult Injured
NECRO
SIS
APOP
TOSIS
REGENERATE

17. Conceptual pathophysiology of AKI
Hemodynamic and
Endothelial
TubularInflammation effect
Activation
Dysfunction
Apoptosis
Cytokine release
Permeability
➡RBF
Lethal : Cell death
Sublethal:
- cytoskeleton disruption
- loss of polarity
- loss off tight junction
- tubular obstruction
- backleak phenomenon
WBC aggregation
Dendritic activation
Cytokine release
Tissue margination
Reduced GFR/
Function loss
Adapted from: Nature review of Nephrology 2012
Injury

18. Conceptual pathophysiology of AKI
Hemodynamic and
Endothelial
TubularInflammation effect
Activation
Dysfunction
Apoptosis
Cytokine release
Permeability
➡RBF
Lethal : Cell death
Sublethal:
- cytoskeleton disruption
- loss of polarity
- loss off tight junction
- tubular obstruction
- backleak phenomenon
WBC aggregation
Dendritic activation
Cytokine release
Tissue margination
Reduced GFR/
Function loss
Adapted from: Nature review of Nephrology 2012
Injury

19. Hemodynamic factor in development
of ATN
Comprehensive clinical nephrology 5th edition : Section XIV Acute Kidney Injury

20. Effect of endothelial disruption
• ↑vascular permeability
• Leukocyte recruitment and activation.
• Activated endothelium ➪ up regulation of
intracellular adhesion molecule 1 (ICAM-1) and P-
selectin
K J Kelly. J Clin Invest. 1996 Feb 15; 97(4): 1056–1063

21. Model of leukocyte extravasation
Robbins and Cotran Pathologic Basis of Disease. 7th ed. Philadelphia: Elsevier Saunders

22. Effects of renal ischemia on histopathology
in ICAM-1–deficient and control mice
K J Kelly. J Clin Invest. 1996 Feb 15; 97(4): 1056–1063
ICAM-1–deficientICAM-1–present

23. Coagulation
• Injured endothelial cell interact with protein C through
endothelial cell protein C receptor (EPCR) and thrombomodulin
• Activated protein C
• antithrombotic actions
• antiinflammatory
• cytoprotective pathways to restore normal homeostasis
• During inflammatory response, protein C, are consumed along
with downregulation EPCR and thrombomodulin expression
Bernard GR, et al.. N Engl J Med. 2001;344:699–709.

24. Multiple protective effect of
activated protein C
Adapted from Bernard GR, et al.. N Engl J Med. 2001;344:699–709.

25. Activation of protein C
Faust el al. NEJM 2001; 345:408-16 27

26. Endothelial cell activation and injury
Sharfuddin, A.Nat. Rev. Nephrol. doi:10.1038/nrneph.2011.16

27. Conceptual pathophysiology of AKI
Hemodynamic and
Endothelial
TubularInflammation effect
Activation
Dysfunction
Apoptosis
Cytokine release
Permeability
➡RBF
Lethal : Cell death
Sublethal:
- cytoskeleton disruption
- loss of polarity
- loss off tight junction
- tubular obstruction
- backleak phenomenon
WBC aggregation
Dendritic activation
Cytokine release
Tissue margination
Reduced GFR/
Function loss
Adapted from: Nature review of Nephrology 2012
Injury

28. Inflammatory response in AKI
• Dendritic cells and macrophages respond to
bacterial structures called pathogen-associated
molecular patterns (PAMPs),
• Tissue damage (eg IRI) is recognized intracellular
proteins (heat shock proteins, and HMBG1.)
released by dead cells called alarmin
• Danger model = Endogenous alarmins and
exogenous PAMPs can be considered subgroups of
damage-associated molecular patterns (DAMPs).
Matzinger P, Science. 2002;296(5566):301
Rosin DL, J Am Soc Nephrol. 2011 Mar;22(3):416-25

29. Danger & Stranger model
J Am Soc Nephrol. 2011 Mar;22(3):416-25

30. Key Inflammatory response after IRI
• Initiated by endothelial dysfunction with
leukocyte extravasation
• Macrophage release of proinflammatory
cytokines (TNF- 𝛼, IL-8,IL-1)
• Chemotactic cytokines (e.g., monocyte
chemoattractant protein-1 [MCP-1] IL-8, RANTES)
• Powerful recruits other inflammatory cells and
complement activation

31. Alterations in microvasculature and
inflammation in ischemic AKI
P.Devarajan et al ; J Am Soc Nephrol 17: 1503–1520, 2006

32. Complement activation
• Complement system generates number of
inflammatory signals that lead to ongoing injury
• Induce recruitment of neutrophils and directly
damages endothelium and surrounding cells.
• Activation of alternative and lectin pathway
(forms membrane attack complex (C5-C9) may
contribute to renal injury
Thurman JM, Kidney Int. 2005;67(2):524.
B.Vries,Am J Pathol. 2004 Nov; 165(5): 1677–1688.

33. Three pathways of complement
activation
B.Vries,Am J Pathol. 2004 Nov; 165(5): 1677–1688.

34. Ischemia followed by reperfusion leads to
renal deposition of
MBL(mannose binding lectin)
B.Vries,Am J Pathol. 2004 Nov; 165(5): 1677–1688.

35. Complement activation in kidneys with ATN
occurs via the alternative complement
pathway.
P.Devarajan et al ,Kidney Int. 2005;67(2):524.

37. Conceptual pathophysiology of AKI
Hemodynamic and
Endothelial
TubularInflammation effect
Activation
Dysfunction
Apoptosis
Cytokine release
Permeability
➡RBF
Sublethal:
- cytoskeleton disruption
- loss of polarity
- loss off tight junction
- tubular obstruction
- backleak phenomenon
Lethal : Cell death
WBC aggregation
Dendritic activation
Cytokine release
Tissue margination
Reduced GFR/
Function loss
Adapted from: Nature review of Nephrology 2012
Injury

38. Sites of tubular injury
in acute tubular necrosis
• S3 segment and medullary TAL
is most damaged area during ischemic injury
• Limited anaerobic glycolysis
• Marked hypoperfusion and congestion area
• Highly metabolised due to reabsorption
Comprehensive clinical nephrology 5th edition : Section XIV Acute Kidney Injury

39. Regional blood flow is altered
following injury in ischemic AKI
Karlberg L. Acta Physiologica Scandinavica. 1983;118:11–17.

40. IRI leads to loss of polarity
• Ischemia-induced redistribution of membrane
proteins
• Disrupts beta-1 integrins protein which regulate
actin–spectrin cytoskeleton cytoskeleton that
anchors the Na-K-ATPase pump lead to
redistribution
• This redistribution of pump results in loss of
bidirectional transport of Na and water resulting
high FeNa in ATN
Schrier RW et al , J Clin Invest. 2006;116(2):357.

41. Tubular Epithelial Cell Injury and the
Development of Acute Tubular Necrosis
Adapted from Schrier RW. J Clin Invest. 2004;114:5-14.

42. Backleak Phenomenon
• ATP depletion induces rapid disruption of actin
cytoskeleton result in loss of tight junctions
• Increased paracellular permeability producing backleak of
the glomerular filtrate into interstitial
• Interstitial edema play major role in decreased blood flow
and exacerbating tubular injury during extension phase
Asif A et al, Nature Reviews Nephrology 7, 189-200 April 2011

43. CYTOSKELETAL AND INTRACELLULAR
STRUCTURAL CHANGES
Sharfuddin A: Encyclopedia of intensive care medicine, New York, 2012, Springer
Loss of filamentous F-actin
(Proximal tubule microvilli)
Loss of tight junction
paracellular transport
(Backleak Phenomenon)
Loss of polarity
Disruption
of integrins with ECM

44. Intratubular obstruction
• Tubular cells bind to beta1-integrin ligands on
basement membrane
• minimize tubule cell detachment and intratubular
obstruction
• Intraluminal casts and Tamm-Horsfall protein,
converted to gel-like polymer in high local luminal
sodium concentrations
J Am Soc Nephrol. 2005;16(2):374

45. Kidney Int. 2001;59(3):932
J Am Soc Nephrol. 2005;16(2):374
Classical muddy brown granular casts.

46. Endothelial-tubular interaction in
ATN
J. Gary Abuelo,N Engl J Med 2007; 357:797-805

47. Cell death and regeneration

48. Alterations in tubule cell structure
after Ischemic reperfusion injury
initiation phase
P.Devarajan et al. J Am Soc Nephrol 17: 1503–1520, 2012
extension phase
initiation phase
sublethal injury
maintenance phase
stem cells and progenitor cells?
Inhibition of apoptosis and inflammation at extension stage
may represent a powerful therapeutic approach
recovery phase

49. Apoptotic pathway
A. Linkermann, J Am Soc Nephrol. 2014 Dec; 25(12): 2689–2701.

50. Four-phase model of necrosis
A. Linkermann, J Am Soc Nephrol. 2006 Dec; 25(12): 2689–2701.

51. Necrosis : is it really unprogrammed?
• Necrosis
• cytoplasmic and organelle swelling
• loss of cell membrane integrity
• release of cellular contents into extracellular space
• inflammatory response within the tissue
• Believed form of accidental uncontrolled cell death w/o signal
• Nowadays general agreement that necrosis can occur in a regulated
manner
• Two special forms of regulated necrosis are necroptosis and parthanatos.
Sandra M., Clinical Kidney Journal, 2015, vol. 8, no. 5, 548–559

52. Necroptosis : New pathway of death

53. Signalling pathways of different cell
death modes
Sandra M., Clinical Kidney Journal, 2015, vol. 8, no. 5, 548–559

54. Programmed Cell Death ≠ Apoptosis
A.Linkermann, N Engl J Med 2014;370:455-65.

55. Necroptosis
• Consequence of death receptor
• Signal 1 : signalling upon formation of RIPK1
• Regulated necrosis, started by TNFR1 ligation (inhibited by RIP1-targeting
chemical necrostatin-1)
• Triggers: FAS/CD95, TRAILR (TNF-related apoptosis-inducing ligand
receptor), TLR3/4 (Toll-like receptor), etoposide and IRI (ischaemia-
reperfusion injury)
• RIPK3/mixed lineage kinase domain-like protein (MLKL) containing
necroptosome
• Signal 2 : Opening mitochondria permeability transition (MPT) pore
• Upon MPT pore opening and apoptosome-forming proteins
• Induce apoptotic phenotype in a caspase-independent mannere
Allam R, J Am Soc Nephrol 2012; 23: 1375–1388
Sandra M., Clinical Kidney Journal, 2015, vol. 8, no. 5, 548–559

56. Major signal in Necroptosis
A.Linkermann, Kidney International (2016) 89, 46–57

57. Difference between apoptosis,
necroptosis and necrosis
Apoptosis Necroptosis Necrosis
Type of cell death Controlled Controlled Uncontrolled
Trigger
Trauma, toxic stress, self-renew,
aging, development.
Trauma, toxic stress, infection
Trauma, toxic stress,
infection
Morphology
Extensive membrane blebbing,
condensation and fragmentation
of the nucleus
Cytoplasmic swelling, rupture of the
plasma membrane and spilling of
the intracellular content
Extensive organelle and cell
swelling, loss of membrane
integrity, release of extracellular
contents
Signalling pathway
Specific, intrinsic or extrinsic
pathways
Specific, e.g TNFR1 pathway Unspecific
Executioner
Caspase, (caspase-3, -6, -7, -8
and -9)
RIP kinase (RIPK1 and RIPK3) -
Inhibitor Z-VAD fmk Necrostatin-1 -
Adapted from A. Linkermann et al. Cell Death Dis. 2015 Nov; 6(11): e1975.

58. Promising intervention to control
regulated necrosis
A.Linkermann, Kidney International (2016) 89, 46–57

59. Take home

60. Thank you for your attention