Monoclonal Free Light Chains and Renal Damage

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Monoclonal Free Light Chains and Renal Damage

• Paul W. Sanders, M.D.
• University of Alabama at Birmingham,
• Birmingham VA Medical Center,
• Birmingham, AL, USA

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Objectives

• Review the renal tubular handling of
  immunoglobulin free light chains

• Discuss the major tubulo-interstitial renal
  lesions associated with light chains
• Interstitial inflammation/fibrosis
• Cast nephropathy

Approach to management
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Glomerular ultrafiltration of macromolecules
classical view
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Megalin and cubilin are multi-ligand receptors in
brush border of the PT
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Proximal tubular epithelial cell
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Light chain nephrotoxicity

• The many and varied lesions associated with light
  chains occur in part because of potential
  interaction with all parts of the nephron.
• Nephrotoxic potential of light chains is
  dependent upon their physico-chemical composition
  as well as environmental influences.
• These factors determine the type and severity of
  the kidney damage that occurs.

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Renal failure in multiple myeloma

• Necropsy study of 57 patients showed renal
  lesions in almost 49 (Iványi, Arch. Pathol. Lab.
  Med. 114986-987, 1990)
• 65 of those patients had cast nephropathy
• 21 had AL-amyloidosis
• 11 had monoclonal light chain deposition disease
• All these lesions are related to deposition of
  free light chain components of immunoglobulin

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Tubulo-interstitial inflammation and fibrosis
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Serum k and l concentrations in multiple myeloma
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Uptake of light chains by HK-2 cells is rapid
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Light chains induce intracellular oxidative stress
HK-2 cells labeled with a green fluorogenic
marker (DCFDA) of ROS.
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1,3-dimethyl-2-thiourea (DMTU), 30 mM, a
chemical trap for H2O2, and pyrrolidine
dithiocarbamate (PDTC), 200 mM, an inhibitor of
NF-kB, inhibited light chain-induced MCP1
production.
Wang and Sanders, J. Am. Soc. Nephrol.
18131-143, 2007
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Redox signalingMechanism of light
chain-mediated activation of the proximal tubule
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Nephrotoxic light chains generate oxidative stress

• Exposure of proximal tubule cells to nephrotoxic
  light chains generates oxidative stress that
  appears to activate c-Src and NF-?B, and
  stimulates production of MCP-1.
• The mechanism appears to be generation of H2O2,
  which can overcome cytoplasmic antioxidant
  defense mechanisms and target reduced sulfhydryl
  groups of cysteine residues to induce activation
  of c-Src.
• Unclear if all light chains are capable of
  generating intracellular oxidative stress.
• May account for tubulo-interstitial
  inflammation/nephritis and interstitial fibrosis
  observed in myeloma.

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Renal Lesion and outcome in myeloma

• Renal biopsy in 118 patients with myeloma and
  renal insufficiency
• 41 had myeloma kidney
• 30 had AL-amyloidosis
• 19 had monoclonal light chain deposition disease
• 10 had chronic tubulointerstitial nephritis
• Prognosis dependent on underlying pathology
• Multi-drug therapy tended to prolong survival and
  slow progression to end-stage kidney disease.

Montseny, et al. Nephrol. Dial. Transplant.
131438, 1998
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Light chain casts with interstitial inflammation
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Microperfusion of the nephron with light chain
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Dissected microperfused tubule showing cast
formation
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Pathogenesis of cast nephropathy

• Cast formation was dependent on the presence of
  Tamm-Horsfall protein.
• The initial site of cast formation was in the
  distal nephron.
• Cast formation was dependent on the type and
  concentration of light chain in the tubular fluid.

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Immunofluorescence micrographs of kidney tissue
from a patient with cast nephropathy (serum l
light chain concentration was 32 mg/ml). The
merged image (middle panel) shows co-localization
(yellow) in the casts. The section has been
counterstained with Hoescht to identify cells
(blue nuclei).
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Tamm-Horsfall protein
The ZP domain is responsible for homotypic
polymerization of THP into filaments
Adapted from Jovine et al., Nature Cell Biology,
June 2002
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Serum free light chains (sFLC) in myeloma

• Baseline sFLC gt 750 mg/L associated with
  creatinine 2 mg/dl and bone marrow
  plasmacytosis gt 30 (Rhee, et al., Blood 110827,
  2007).
• sFLC reduction essential for recovery
  particularly in cast nephropathy.
• Multiple factors modulate cast formation,
  including state of hydration, concentration and
  CDR3 sequence of the light chain in the tubular
  fluid, concentration of Tamm-Horsfall protein,
  presence of furosemide, and the ambient
  concentrations of calcium, sodium and protons.

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Volume status determines the rate of cast
formation
The light chain was obtained from a patient who
had cast nephropathy. When purified, the light
chain readily co-aggregated with Tamm-Horsfall
protein. Perfusate light chain concentration was
1 mg/ml.
J. Clin. Invest. 89630-639, 1992
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Volume status can determine obstruction
The light chain (len) was obtained from a patient
who did not have kidney disease (provided by Dr.
Alan Solomon at the University of Tennessee).
When purified, the light chain did co-aggregate
with Tamm-Horsfall protein, but the affinity was
low.
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Furosemide accelerates obstruction in
dose-dependent fashion
The light chain was obtained from a patient who
had renal failure from cast nephropathy.
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Clinical factors aggravating cast formation

• Volume depletion
• Hypercalcemia
• Radiocontrast material
• NSAIAs
• Diuretics

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Treatment of cast nephropathy

• Rapidly lower circulating light chain
  concentration - follow serial serum light chain
  levels
• Increase free water intake to 2-3 liters per day
  as tolerated
• Treat/prevent hypercalcemia, infection and
  perhaps hyperuricemia
• Avoid exposure to loop diuretics, NSAIAs, and
  radiocontrast agents

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Conclusions

• Light chains produce a unique form of oxidative
  stress that activates the proximal tubule to
  promote elaboration of an inflammatory mediator,
  MCP-1.
• Light chains co-precipitate with THP, producing
  intraluminal casts that obstruct tubule fluid
  flow in the distal nephron.
• Both mechanisms may participate in the
  progression of chronic kidney disease observed in
  multiple myeloma.

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Collaborators and funding

• Beverly B. Booker
• Herbert C. Cheung
• Guillermo A. Herrera
• Zhi-Qiang Huang
• Wei-Zhong Ying
• Betsy Wang
• Kristal Aaron