WO1994008612A1

WO1994008612A1 - New method of protecting central nervous system against damage resulting from cerebrovascular or neuronal compromise

Info

Publication number: WO1994008612A1
Application number: PCT/US1993/010098
Authority: WO
Inventors: Peter G. Thomas
Original assignee: Thomas Peter G
Priority date: 1992-10-22
Filing date: 1993-10-19
Publication date: 1994-04-28
Also published as: AU5365494A

Abstract

Protection against or amelioration of cerebral vasospasm or neuronal compromise is obtained by administration of histidine or its salts, derivatives or analogs to the CNS cells or tissues. Histidine could also be combined with other therapeutic agents.

Description

NEW METHOD OF PROTECTING CENTRAL NERVOUS SYSTEM AGAINST DAMAGE RESULTING FROM CEREBROVASCULAR OR NEURONAL COMPROMISE

The present invention is related generally to methods of protecting cerebral tissues against ischemic damage and vasospasm. More particularly, the present invention is related to a new method of protecting central nervous system (CNS) cells or tissues against ischemic neurological deficits, vasospasm or neuronal insult.

Cerebral vasospasm accompanying and following aneurysmal subarachnoid hemorrhage (SAH) , neurosurgery, head injury, stroke, infectious diseases, etc., is one of the most important causes of cerebral ischemia, and is the leading cause of death and disability after aneurysm rupture.

(Kassell et al, 1985, Stroke. 16:562-572; Scheld et al, 1990,

Annals of Int. Med. 112:612-623; Rozsa et al, 1989, Radiolo ia

Diaqnostica. 151-157) . Clinical vasospasm causes cerebral damage from ischemic arterial narrowing. However, the pathogenesis of cerebral vasospasm is not definitively determined. Studies thus far have failed to yield conclusive evidence as to the causative agent(s) or the nature of the arterial narrowing. It remains unclear whether or not vasospasm is a normal or abnormal contraction or failure of relaxation of arterial smooth muscle cells, and whether or not it represents a cytoarchitectural thickening in the vessel wall (Kassell et al, supra) . The delayed, prolonged, irreversible arterial narrowing which occurs after SAH, for example, appears to be much different from the vasospasm observed in the coronary circulation of patients, such as seen in Prinzmetal's variant angina.

The prevention or reversal of neuronal ischemic deficits from vasospasm can be considered in three categories: First, measures to improve blood flow by altering the rheological characteristics of the blood; second, measures to improve oxygen delivered to the cerebral tissues; and third, hemodynamic measures to increase cerebral blood flow. However, these approaches are generally complicated, hazardous, and non-physiological and should be considered primarily interim solutions until measures for specifically preventing or reversing the arterial narrowing can be developed (Kassell et al, vide supra) . SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide an effective method of controlling damage to the central nervous system resulting from such conditions as ischemic neurological deficits, vasospasm, inflammation, infection, injury, or changes in the level or function of neurotransmitters and the like.

Other objects and advantages will become evident from the following detailed description of the invention. BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects, features, and many of the attendant advantages of the invention will be better understood upon a reading of the following detailed description when considered in connection with the accompanying drawings, wherein:

Figure l shows the effect of different amounts of histidine on SAH-induced vasospasm. DETAILED DESCRIPTION OF THE INVENTION

The above and various other objects and advantages of the present invention are achieved by a new method of protecting the central nervous system against or ameliorating damage resulting from, but not limited to, such conditions as ischemic neurological deficits, vasospasm, inflammation, injury, infection, or changes in the level or function of neurotransmitters, comprising the step of administering a sufficient amount of histidine or its salts, derivatives, analogs, and the like, to the cells or tissues in the CNS susceptible to damage resulting from cerebrovascular, inflammatory, infectious or other neuronal insults, to protect against or ameliorate said damage.

It is noted that unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or eguivalent to those described herein can be used in the practice or testing of the present invention, the methods and materials described herein are preferred. Unless mentioned otherwise, the techniques employed or contemplated herein are standard methodologies well known to one of ordinary skill in the art. The materials, methods and examples are only illustrative and not limiting.

The term "cerebrovascular or neuronal compromise" as used herein means any change due to any cause in the normal condition or function of the cerebrovascular or neuronal cell or tissue in the central nervous system, and the resultant effect thereof. Some of such causes and effects have been mentioned elsewhere in this application.

The term "protecting" as used herein includes prevention, amelioration, reversal or in any manner controlling damage to any CNS cell or tissue where ischemia, vasospasm, infection, physical damage or other causes of impaired neuronal functions are involved.

The standard orphometric method employed in the study of vasospasm is now set forth. The method includes analysis of fixed histological arterial cross-sections to measure luminal diameters in animal models of chronic cerebral vasospasm as described in detail by Lehman et al, in Cerebral Vasospasm. ed. Robert H. Williams, Raven Press, New York, N.Y. pp 113- 117.

MATERIALS AND METHODS Effect of Histidine on Vasospasm

Each of 12 New Zealand white rabbits, weighing 4 to 5 kg. had two transfermoral vertebrobasilar angiograms performed 3 1/2 days apart. Twelve hours after the first angiogra , six of the 12 rabbits were subjected to experimental subarachnoid hemorrhage (SAH) . The other six rabbits served as controls and underwent only angiography. SAH was induced by the percutaneous injection of 1 ml/kg of autologous, non- heparinized arterial blood into the cisterna magna. Seventy- two hours after the SAH, the rabbits underwent their second angiogram and were sacrificed by perfusion-fixation. The cross-sectional area of the basilar artery was measured and processed for light and electron microscopy. Effect of histidine on synaptic transmission For this study, adult Sprague-Dawley rats weighing 150-

200 g are anesthetized with ether and sacrificed by decapitation. The basic procedures for preparing cortical brain slices are similar to those described previously for rat cortex (Lee, 1982, Brain Research. 239:617-623). Briefly, the brains are rapidly removed and placed in cold artificial cerebrospinal fluid (ACSF) . The ACSF consists of the following (in mM) : 110.2 NaCl, 2.9 KC1, 1.1 KH₂P0₄ , 2.1 MgS0₄ , 1.8 CaCl₂ , 22.8 NaHC0₃ , 8.9 glucose. Using a razor blade, the brains are first hemisected at the midline, and then one of the hemispheres was bisected in a horizontal plane followed by a sagittal section. The superior-lateral quadrant of this dissection is placed on a tissue chopper and brain slices were cut in a coronal plane at a thickness of 400 mm. Brain slices containing the parietal cortex at the level of the striatum are placed in a petri dish containing ACSF. Slices are then transferred to a holding chamber held at 35.5 C and maintained at interface with a humidified atmoshpere of 95% 0₂ : 5% C0₂ (i.e. normoxic conditions). After a post-sacrifice period of at least one hour, slices are transferred to a recording chamber as required. A bipolar stimulating electrode is positioned under visual guidance near the layer IV - layer V border in the slice. A glass microelectrode filled with 3 M NaCl (1-5 megaohm) is placed in layer III above the position of the stimulating electrode. Stimuli are delivered once every fifteen seconds and the amplitude of evoked cortical potentials measured in response to a range of stimulation intensities. During the course of an experiment, stimuli are administered at an intensity adjusted to elicit a response of approximately 60% of the maximal amplitude. Hypoxic conditions are achieved by substituting 99% N₂ for the normal 95% 0₂ :5% C0 in the atmosphere of the recording chamber. The standard temperature in the recording chamber is 35.5 C.

A stable baseline of evoked responses is established under normoxic conditions for at least 15 minutes. Histidine (10 - 100 mM) or standard ACSF is then perfused for the remainder of the experiment. After 15 minutes of perfusion with histidine, hypoxic conditions are initiated. Hypoxic conditions were maintained until 10 minutes following the occurrence of hypoxic depolarization after which the slices are reoxygenated. Slices are monitored continuously for one hour following reoxygenation.

The neuroprotective effect of histidine is determined by comparing the recovery of evoked responses following hypoxia in control and histidine-treated slices. Results

Figure 1 shows the effect of histidine on SAH-induced vasospasm. The data clearly show the reversal of arterial constriction by histidine. Significantly pronounced effects were observed with dosages of 50 mg and 100 mg histidine administered 2x/day and 4x/day, respectively.

Additionally, when hypoxic parietal cortex slices were treated with histidine, increased synaptic transmission was observed (data not shown) .

These results indicate the utility of histidine in effectively controlling damage to the CNS resulting from cerebrovascular or neuronal compromise.

Of course, histidine or its salts, derivatives or analogs can be administered in a pharmaceutically acceptable vehicle by any suitable route, e.g., intracerebrally into the cerebrospinal fluid or blood stream, intrathecally, intravenously, sublingually and the like. Although histidine was provided as a free base in the experiments described herein, it could be easily provided as a salt (e.g., monohydrochloride monohydrate) or as a dipeptide. Either L-, D- or DL-histidine could be used and any one of these isomeric forms could be administered in a preventive or therapeutic regimen. Furthermore, as would be easily suggested to the skilled artisan, histidine could be combined with other therapeutics, such as antibiotics, calcium channel blockers, anticoagulative, antiplatelet and thrombolytic agents, free radical scavengers, antibodies, other amino acids, and the like, for example heparin, warfarin, aspirin, TPA, streptokinase, APSAC, superoxide dismutase, catalase, mannitol, deferoxamine, nifedipine, verapamil, etc.

It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.

Claims

Claim 1. A method of protecting against or ameliorating damage to the central nervous system cell or tissue, comprising the step of: administering an effective amount of histidine to a patient in need thereof, to protect against or reverse damage to neuronal tissue or the central nervous system.

Claim 2. A method, as recited in claim 1, wherein said step of administering is achieved via a route selected from the group consisting of intracerebrally and intrathecally and intravenously and sublingually.

Claim 3. A method, as recited in claim 1, wherein said histidine is L - histidine or a salt, derivative or analog of histidine which can be reduced to L-histidine.

Claim 4. A method, as recited in claim 1, wherein said histidine is in L or D form or a salt, derivative or analog of histidine which can be reduced to L or D histidine.

Claim 5. A method, as recited in claim 1, wherein said effective amount of histidine is in the range of approximately 20 mg/kg to 100 mg/kg.

Claim 6. A method of ameliorating damage or protecting against cerebral vasospasms, comprising the step of: administering an effective amount of histidine to a patient in need thereof, to protect against or reverse arterial narrowing.

Claim 7. A method, as recited in claim 6, wherein said effective amount of histidine is in the range of approximately 20 mg/kg to 100 mg/kg.

Claim 8. A method of protecting against or ameliorating damage to the central nervous system cell or tissue, comprising the step of

administering an effective amount of histidine to a patient in need thereof, to increase synaptic transmission.