How Does CSD Protect the Brain

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How Does CSD Protect the Brain against
Ischemia? Frank A. Welsh Department of
Neurosurgery University of Pennsylvania
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CSD Induces Tolerance to Ischemia
pMCAO
CSD
pMCAO
(Otori et al., 2003)
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Induced Tolerance
Any Cell
Lethal Insult
Sublethal Insult
Lethal Insult
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Rat Models of CSD-induced Tolerance to Ischemia
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Stages of CSD-induced Tolerance to Ischemia
CSD
Tolerant
Non-tolerant
Sensors Depolarization? NMDA receptor?
Signaling Pathways Calcium ion entry? NO
synthesis? Protein kinases? Cytokines?
Effectors Trophic factors? Stress
proteins? Glutamate transporters?
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Proteins Not Upregulated by CSD
Heat-shock protein-72 (Kobayashi et al.
1995) Glutamine Synthetase (Karikó et al.,
1998) SOD-1, SOD-2 (Mitchell et al., 2001)
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Proteins Upregulated after CSD
Trophic Factors NGF (Herrera et al.,
1993) BDNF (Kokaia et al., 1993) bFGF
(Kawahara et al., 1999) Stress Protein hsp27
(Plumier et al., 1997) ACh Receptor a7 nAChR
(Chazot et al., 2003) Protein kinases PKCd
(Koponen et al., 1999 Kurkinen et al.
2001) ERK (Chow et al., 2002) Protease tPA
(Karikó et al., 1998) Glutathione
metabolism Glutathione-S-transferase-5 (Choudhuri
et al., 2002) cGMP/vasodilation Atrial
natriuretic peptide (Wiggins et al.,
2003a) Prostaglandin metabolism COX-2 (Miettinen
et al., 1997) NO-signaling nNOS (Caggiano and
Kraig, 1998) Anti-apoptotic Clusterin (Wiggins
et al., 2003b)
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Proteins Downregulated after CSD The Glutamate
Hypothesis
CSD downregulates the glial glutamate
transporters, EAAT1 and EAAT2 (Douen et al.,
2000). Preconditioning with CSD attenuates the
increase in extracellular glutamate that occurs
during ischemia (Douen et al., 2000). Thus,
downregulation of EAAT1 and EAAT2 may diminish
backwards flux of glutamate during ischemia.
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The First Signs of Protection?
CBF
Cell Death
Energy failure
Glutamate release
Calcium entry
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Effect of CSD on CBF during Ischemia
Effect on CBF Method used Matsushima et
al. (1996) None detected H-clearance Yanamoto
et al. (1998) None detected
LDF/H-clearance Otori et al. (2003) Increased
LDF
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Preconditioning with CSD improves LDF
CSD-preconditioned

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LDF ( of Baseline)
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Sham-conditioned
30 min 60 min 90 min
120 min MCA occlusion
(Otori et al., 2003)
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Laser-Doppler Flowmetry
100
80
60
LDF ( of Baseline)
CSD-preconditioned
40
20
Sham-conditioned
MCA Occlusion
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CSD Decreases Baseline CBF
300
LDF ( of Baseline)
200
100
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Is baseline CBF altered 3 days after CSD?
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CBF in Cortex 3 days after CSD
Cx1
Cx2
Cx3
(Otori et al., 2003)
Cx4
Cx5
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Laser-Doppler Flowmetry
100
80
60
LDF ( of Baseline)
40
CSD-preconditioned
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Sham-conditioned
MCA Occlusion
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• Conclusions
• 1. CSD causes long-lasting decrease in baseline
  CBF.
• 2. CSD causes increase in relative CBF, but not
• absolute CBF during MCA occlusion.
• Questions
• What is the cause of decreased CBF after CSD?
• 1. Abnormal vasoconstriction with normal CMR?
• 2. Normal vasoconstriction with reduced CMR?

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CMRG in Cortex 3 days after CSD
Sham
1.4
1.2
1.0
CSD
CMRG (µmol/g/min)
0.8
0.6
0.4
0.2
Par Temp Occ Cing Ent Region of
Cortex
Adapted from Kawahara et al., Neurology
15827-36, 1999
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CONCLUSIONS

• CSD decreases baseline CMRG and CBF.
• CSD increases CBF/CMRG during MCAO.
• Increased CBF/CMRG preserves ATP.
• Preserved ATP attenuates infarction.

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KCl triggers CSD and a small lesion
5 M KCl
CSD
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Does a lesion without CSD induce tolerance?
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0.9 NaCl (n8)
5 M NaCl (n8)
Infarct Volumes
Cortex 194 55 mm³ 127 48 mm³
(plt0.05) Subcortex 91 16 mm³ 77 5
mm³ (plt0.05)
(Muramatsu and Welsh, 2003)
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SUMMARY

• CSD protects against global and focal ischemia
• CSD alters expression of many proteins
• CSD decreases baseline CMRG and CBF
• CSD improves CBF during focal ischemia
• Cortical lesion induces tolerance without CSD