Role of β-adrenoreceptor partial agonist in pathophysiology and recovery of ischemic stroke

Sezen Kislal1*, Kristine Ravina1*, Zuha Warraich1, Mehrdad Shamloo1

Neurosurgery, School of Medicine; Stanford University, Palo Alto, CA, USA1

Noradrenaline plays significant role in modulating metabolic and

inflammatory activity within the brain by activating receptors on

glial cells and neurons 2,4,5. Our previous results in a mouse model

of Alzheimer’s disease overexpressing human amyloid precursor

protein, have shown that chronic treatment with xamoterol (a

selective β1-adrenoreceptor partial agonist) significantly enhances

cognitive function, reduces inflammatory cytokine levels and

modulates microglial activity (Figure 1 and 2).

We therefore investigated the effect of chronic xamoterol dosing

on stroke recovery by implementing intraluminal filament method

of transient middle cerebral artery occlusion in male Sprague-

Dawley rats. Starting 24h post-stroke, animals received vehicle or

0.1, 1 or 3 mg/kg dose of xamoterol subcutaneously for 21 days.

Brain tissue immunohistochemical assessment of neuronal loss

displayed smaller infarction in animals treated with xamoterol

daily in comparison to the vehicle group.

To evaluate whether the effect of 1 mg/kg dose on post-stroke

functional recovery is treatment time-dependent, we initiated

xamoterol treatment at 24 or 72 h after the onset of ischemia. In

Garcia neurological scoring test and vibrissae elicited forelimb

placement (paw-whisker) test the 72h post-stroke treatment group

showed improved recovery in comparison to 24h post-stroke

group.

Background Results

Acknowledgements

Method

Work in Progress

References

Starting 24 hr or 72 hr post-stroke, animals received 1 mg/kg dose of

xamoterol subcutaneously for 36 days.

Starting 24h post-stroke, animals received vehicle or 0.1, 1 or 3 mg/kg

dose of xamoterol subcutaneously for 21 days.

Figure 3. Treatment with xamoterol, a functionally selective partial agonist of ADRB1 starting at 24h post stroke

reduces ischemic brain injury. *p<0.05

Treatment started at 24 h (NeuN staining) Treatment started at 24 h (Cresyl Violet staining)

Stroke

Induction

Figure 4. A tendency for improvement in behavioral function

measured by Garcia neurological score was seen in xamoterol

treatment groups.

Treatment started at 24 h Treatment started at 24 or 72 h

Figure 5. A tendency for improvement in behavioral function

measured by Paw-whisker test was seen in 72h post-stroke treatment

group.

• Developing mechanistic tools and paradigms for identifying cell type

and receptor subtype specificity for the adrenergic modulation of

stroke-related behavior and pathology.

• Determining the role of ADRB1 and ADRB2 adrenergic tone on

stroke-related behavior deficits and pathology and the mechanistic

basis of adrenergic receptor subtype tone on astrocyte function.

Cresyl Violet Staining

Vehicle

Xamoterol 1mg/kg

NeuN Staining

Vehicle Xamoterol 1mg/kg

90 min transient MCAO model

Conclusion

This study was partially supported by the P30 2P30NS069375-06.

Iba 1 Staining

Xamoterol 1mg/kg

Vehicle

Behavioral Testing

Garcia Neurological Score : It is a composite neurological test in which the rats are evaluated for various sensorimotor deficits1.

The Garcia test is a composite neurological test in which the rats are put through a series of 6 different tests: 1.Spontaneous activity, 2. Symmetry in

forelimbs movement, 3. Forepaw outstretching, 4. Climbing, 5. Body proprioception, 6. Response to vibrissae touch, for which they are given scores on a 3

point scale.

Paw- whisker (The vibrissae-evoked forelimb placing test): It is used to assess asymmetry in the sensorimotor cortex and striatum 3. The experimenter

holds the animal such that all four limbs hang freely. The vibrissae are stimulated by brushing each side against the edge of a table. This elicits a same-side

forelimb response to place the paw on the table top. The rat is allowed ten trials on each side and the percent of successful placements is recorded.

BLA

* *

Our results suggest that mild activation of β1-adrenoreceptors during early

phase post-stroke (24-72 hours) exerts neuroprotective properties and can also

enhance the recovery of function. Further research is necessary to investigate

molecular and cellular aspects of adrenergic stimulation in the pathophysiology

of stroke.

1. Garcia JH, Wagner S, Liu KF, Hu XJ. Neurological deficit and extent of neuronal necrosis attributable to middle cerebral

artery occlusion in rats. Statistical validation. Stroke. 1995; 26:627–34. discussion 35. [PubMed: 7709410]

2. Junker, V., Becker, A., Hühne, R., Zembatov, M., Ravati, A., Culmsee, C., & Krieglstein, J. (2002). Stimulation of β-

adrenoceptors activates astrocytes and provides neuroprotection. European journal of pharmacology, 446(1), 25-36.

3. Schallert T, Fleming SM, Leasure JL, Tillerson JL, Bland ST. CNS plasticity and assessment of forelimb sensorimotor

outcome in unilateral rat models of stroke, cortical ablation, parkinsonism and spinal cord injury. Neuropharmacology.

2000; 39:777–87. [PubMed: 10699444]

4. Semkova, I., Schilling, M., Henrich-Noack, P., Rami, A., & Krieglstein, J. (1996). Clenbuterol protects mouse cerebral

cortex and rat hippocampus from ischemic damage and attenuates glutamate neurotoxicity in cultured hippocampal

neurons by induction of NGF. Brain research, 717(1), 44-54.

5. Semkova, I., & Krieglstein, J. (1999). Neuroprotection mediated via neurotrophic factors and induction of neurotrophic

factors. Brain research reviews, 30(2), 176-188.

* Shared first authorship

Stroke

Induction

BLA

0

10

20

wildtype 5XFAD

VEH XAM VEH XAM

*

**

IBA

1-i

r (m

ean

gra

y v

alu

e)

Figure 1. Stimulation of ADRB1 attenuates Iba-1 protein expression

levels in basolateral amygdala (BLA), mouse model of Alzheimer’s

disease.

Figure 2. In the 5X FAD mouse model, chronic dosing with the ADRB1

agonist, xamoterol, rescued cognitive deficits in a novel object test (A) and

long-term spatial memory in morris-water maze test (B). *p=0.05