Ineffectiveness of dimethyl sulfoxide in altering the permeability of the blood-brain barrier

Evaluation of the neurotoxicity of DMSO infused into the carotid artery of rat

INTRODUCTION

Despite the explanations put forth in many studies regarding histopathological evidence of the inflammatory stage related with the infusion of dimethyl sulfoxide (DMSO) in the vessel wall and its lumen, there has been no research to evaluate its neural toxicity when it is infused via the intracarotid route. This study was designed to evaluate the possible neurotoxic effects of DMSO on the closer and distant brain tissue and carotid artery when it was slowly infused into the internal carotid arteries of the rats.

METHODS

The right common carotid artery bifurcation was exposed through a midline neck incision, and then except those of the control group animals (n=5), the experimental material (normal saline, n=5 or anhydrous DMSO, n=10) was infused into the internal carotid artery of the Wistar albino rats. After the experimental materials were administered intra-arterially, brain tissues were harvested for histopathological and biochemical studies at 72 h for investigation of the acute stage changes and on 10th day for investigation of the chronic stage changes. Internal carotid arteries of both sides were also removed for histopathological evaluation. During sacrification of the rats, whole body blood of them are collected for biochemical evaluation.

RESULTS

There was no statistically significant difference between the groups regarding comparison of the mean values of the hippocampal neuronal cell counts and the carotid artery diameters in both acute and chronic stages. Also, mean values of the lipid peroxidation levels of harvested brain tissues and serums of the collected bloods were similar in control, saline and DMSO groups.

CONCLUSION

This experimental study suggested that DMSO has no toxic effect on the neural and arterial tissues of rats when it is slowly infused into the carotid artery.

Transport into brain of buthionine sulfoximine, an inhibitor of glutathione synthesis, is facilitated by esterification and administration of dimethylsulfoxide

Buthionine sulfoximine (BSO), an inhibitor of glutathione synthesis, is poorly transported into the brain of adult mice, and only a slight decrease (approximately 10%) in the level of brain glutathione is found 30-60 min after intraperitoneal administration of BSO. When BSO is given as the ethyl ester, the brain level of BSO increases substantially after 5-15 min, and the glutathione level decreases by about 25% after 30-60 min. When BSO or its ester is given in 15% dimethylsulfoxide solution the brain levels of BSO are increased significantly and the brain glutathione levels are decreased by 20-35%. These observations suggest procedures that may be useful in decreasing the glutathione levels of the brains of adult animals. The finding that administration of BSO ethyl ester led to about a 25% decrease in the brain level of glutathione within 15 min suggests that a fraction of brain glutathione turns over very rapidly and may therefore be of special physiological significance.

Effect of dimethyl sulfoxide on blood-to-brain transfer of alpha-aminoisobutyric acid: examination of regional blood-brain barrier function

The effect of dimethyl sulfoxide (DMSO) on brain capillary permeability has been controversial. We have studied the effect of DMSO on unidirectional transport of alpha-aminoisobutyric acid (AIB) across the blood-brain barrier (BBB) in rats. Rats were treated with 15% DMSO intraperitoneally (i.p.), intravenously (i.v.) or by an i.p. injection in combination with an i.v. injection, or in some cases intra-arterially by rapid infusion into left external carotid artery. The unidirectional blood-to-brain transfer constant (Ki) for AIB was measured in each group after the animals were killed. DMSO administration did not significantly increase Ki as compared to control Kj. These results show that it is unlikely that DMSO increases the permeability of BBB and therefore do not support the proposal that DMSO can act as a carrier at the BBB for compounds with restricted vascular permeability.

Tubular profiles do not form transendothelial channels through the blood-brain barrier

The contribution of tubular profiles within the mammalian cerebral endothelium to the formation of transcellular channels was analysed following exposure of the endothelium to native horseradish peroxidase (HRP) dissolved in saline or dimethyl sulphoxide (DMSO) administered intravenously in mice. Within 5-15 min, but not at 30 min to 2 h postinjection, peroxidase-positive extravasations were evident within the parenchyma of the forebrain and brainstem of mice exposed and not exposed to DMSO. The extravasations may be associated with the rupture of interendothelial tight junctions at the level of arterioles as a consequence of the perfusion-fixation process. Ultrastructural inspection of endothelia within and away from areas of peroxidase extravasation revealed the following intraendothelial, peroxidase-positive organelles: presumptive endocytic vesicles, endosomes (a prelysosomal compartment), multivesicular and dense bodies, and tubular profiles. Statistical analysis of the concentration of HRP-labelled presumptive endocytic vesicles, which may coalesce to form tubules, within endothelia from mice injected intravenously with HRP-DMSO compared to mice receiving HRP-saline revealed no significant difference. HRP-positive tubular profiles were blunt-ended, variable in length and width, and appeared free in the cytoplasm or in continuity with dense bodies. Labelled tubules free in the cytoplasm were positioned parallel to the luminal and abluminal plasma membranes and were less frequently oblique or perpendicular to these membranes. Tubular profiles analysed in serial thin sections or with a goniometer tilt stage did not establish membrane continuities with the luminal and abluminal plasma membranes. Peroxidase-positive tubular profiles were similar morphologically to those exhibiting acid hydrolase activity but did not share morphological and enzyme cytochemical similarities with the endoplasmic reticulum that stained for glucose-6-phosphatase (G6Pase) activity. G6Pase-positive profiles of endoplasmic reticulum were not observed to contribute to a transendothelial canalicular network. Our results suggest that: (i) peroxidase-labelled tubules, acid hydrolase-positive tubules, and G6Pase-positive endoplasmic reticulum do not form transcellular channels through the cerebral endothelium; (ii) tubular profiles labelled with blood-borne HRP in the cerebral endothelium are associated with the endosome apparatus and/or the lysosomal system of organelles; and (iii) DMSO does not appear to alter the permeability of the blood-brain barrier to blood-borne protein.

Improved delivery through biological membranes XIX: Novel redox carriers for brain-specific chemical delivery systems

New dihydropyridine in equilibrium pyridinium salt-type redox carrier systems were developed in which the drug is linked via the ring nitrogen atom of nicotinamide. The rate of oxidation of the dihydropyridine forms, and thus the overall and brain-specific distribution of the corresponding 3-carbamoyl-1-carbamoylalkyl-drug quaternary salts, depends on the number of methylene groups separating the ring nitrogen and the carbamoyl function linked to the drug.

Little effect of dimethyl sulfoxide on blood-brain barrier to dopamine

Rats were treated with dimethyl sulfoxide (DMSO) intraperitoneally or intravenously, and simultaneously with dopamine (DA). The presence of DMSO resulted in small or no increases in brain levels of DA or its metabolites.

Blood-brain barrier disruption in immature Fischer 344 rats

Methods for transiently disrupting the blood-brain barrier (BBB) which are consistent with survival are described for immature Fischer 344 rats weighing 40 to 99 gm. A catheter was retrogradely inserted into the external carotid artery to the level of the bifurcation. Perfusion of 1.4 M mannitol or 1.6 M arabinose, at a rate of 0.01 to 0.1 ml/sec for 30 seconds, resulted in transient BBB disruption as measured by Evans blue dye (EBD) staining. Higher flow rates or perfusion with 10% to 30% dimethyl sulfoxide were associated with a mortality rate ranging from 0% to 44%. Perfusion with 0.9% sodium chloride or intrafemoral artery perfusion with 1.4 M mannitol did not disrupt the BBB. Optimum BBB disruption as measured by EBD staining was achieved with 1.6 M arabinose at 0.026 ml/sec for 30 seconds, at which time all of the 42 experimental animals had BBB disruption; all of the animals so treated survived 2 weeks following perfusion. This technique will allow the efficacy of delivering chemotherapeutic agents following BBB disruption to be tested in several of the more commonly used small-animal models for brain-tumor research.

Acute dimethyl sulphoxide therapy in experimental brain oedema, effect of dose and concentration on brain water and electrolyte content

Albino rabbits with experimental brain oedema produced by a combined left hemisphere cryogenic injury and a metabolic insult by a 6-aminonicotinamide (6-ANA) were administered intravenous dimethyl sulphoxide (DMSO) in varying concentrations and doses in the following manner: Subgroup A (concentration response) received 1.0 g/kg bolus of a 10, 20, 30, or 40% solution. Subgroup B (dose response) received as a 20% solution a 1.0 g/kg bolus, 1.5 g/kg bolus, or 2.0 g/kg infusion. One hour following administration of the agent, the animals were killed, their brains rapidly removed by craniectomy and brain water, sodium and potassium measured. Significant decreases in brain sodium and water content in the right hemisphere were noted in both subgroups A (p less than 0.05) and B (p less than 0.005) and in the left hemisphere in subgroup B only (p less than 0.005). There is an apparent effect on brain oedema by a DMSO mediated sodium dependent water mobilization.

Morphologic effect of dimethyl sulfoxide on the blood-brain barrier

Dimethyl sulfoxide (DMSO) opens the blood-brain barrier of mice to the enzymatic tracer horseradish peroxidase. A single injection of horseradish peroxidase in 10 to 15 percent DMSO into the tail vein along with 10 to 15 percent DMSO delivered intraperitoneally allowed horseradish peroxidase to fill the extracellular clefts throughout the brain within 2 hours. In the absence of DMSO, peroxidase failed to enter brain parenchyma except through the circumventricular organs. Opening of the blood-brain barrier by DMSO is reversible. Dimethyl sulfoxide stimulated the pinocytosis of horseradish peroxidase by the cerebral endothelium; the peroxidase was then directed to lysosomal dense bodies for degradation. Vesicular transport of horseradish peroxidase from the luminal to the abluminal wall of the endothelial cell was not observed. Dimethyl sulfoxide did not alter the morphology of endothelial cells or brain parenchyma.