Intracerebral transplantation of adult mouse neural progenitor cells into the Niemann-Pick-A mouse leads to a marked decrease in lysosomal storage pathology.

Niemann-Pick disease is caused by a genetic deficiency in acid sphingomyelinase (ASM) leading to the intracellular accumulation of sphingomyelin and cholesterol in lysosomes. In the present study, we evaluated the effects of direct intracerebral transplantation of neural progenitor cells (NPCs) on the brain storage pathology in the ASM knock-out (ASMKO) mouse model of Type A Niemann-Pick disease. NPCs derived from adult mouse brain were genetically modified to express human ASM (hASM) and were transplanted into multiple regions of the ASMKO mouse brain. Transplanted NPCs survived, migrated, and showed region-specific differentiation in the host brain up to 10 weeks after transplantation (the longest time point examined). In vitro, gene-modified NPCs expressed up to 10 times more and released five times more ASM activity into the culture media compared with nontransduced NPCs. In vivo, transplanted cells expressed hASM at levels that were barely detectable by immunostaining but were sufficient for uptake and cross-correction of host cells, leading to reversal of distended lysosomal pathology and regional clearance of sphingomyelin and cholesterol storage. Within the host brain, the area of correction closely overlapped with the distribution of the hASM-modified NPCs. No correction of pathology occurred in brain regions that received transplants of nontransduced NPCs. These results indicate that the presence of transduced NPCs releasing low levels of hASM within the ASMKO mouse brain is necessary and sufficient to reverse lysosomal storage pathology. Potentially, NPCs may serve as a useful gene transfer vehicle for the treatment of CNS pathology in other lysosomal storage diseases and neurodegenerative disorders.

Controlled modulation of BBB permeability using the bradykinin agonist, RMP-7.

Previous studies have shown that the bradykinin agonist, RMP-7, can safely permeabilize the blood brain barrier (BBB) by activation of constitutive B2 receptors on endothelial cells. The paper describes a series of studies using quantitative autoradiography and intracarotid infusions of RMP-7 to further elucidate the effect on BBB permeability. Because earlier studies also demonstrated that even greater effects of RMP-7 were observed in the BBB associated with brain tumors, animal models were employed so that comparisons could be made between the effects of RMP-7 within tumor, brain tissue proximal to tumor, and brain tissue distal from tumor. In the first study, the effect of RMP-7 on enhancing the BBB permeation of three compounds of different physical characteristics was directly compared ([14C]carboplatin, small, hydrophilic; [14C]dextran, large, hydrophilic; [14C]BCNU, small, lipophilic). RMP-7 increased permeability of the vascular barriers to both hydrophilic compounds, carboplatin and dextran. While the effects of RMP-7 were observed on nontumor BBB, the greatest and most consistent effects were observed on the blood brain tumor barrier. This was true for both carboplatin and dextran, with progressively less effect seen as the distance from tumor boundary increased. This topographic effect was more pronounced with the larger molecular weight compound, dextran. No effect of RMP-7 was seen in permeabilizing the BBB or the blood brain tumor barrier for the lipophilic drug, BCNU. In a second study, the generality of RMP-7's effects was established by demonstrating similar increases in permeability to carboplatin in both inbred (Fischer 344) and outbred (Wistar) rat strains, implanted with varying tumor cell lines. Finally, several additional studies were performed to gain greater insight into the dynamics involved with eventual restoration of the BBB following RMP-7 administration. In one series, it was demonstrated that the BBB begins to close nearly immediately upon withdrawal of RMP-7, with complete restoration occurring within minutes. In another series, tachyphylaxis or desensitization resulting from continuous RMP-7 infusion was studied. These studies demonstrated that 60 min of continuous RMP-7 infusion resulted in complete, spontaneous restoration of the barrier to both carboplatin and dextran. Moreover, the desensitization appears to be linked to the initial activation of the receptors in a way which suggests that obligatory desensitization may exist as part of a more complete response. These data are discussed as they relate to practical issues to enhance delivery of drugs across the BBB, as well as more fundamental issues involving the function of the BBB and its interaction with the brain.

Unlocking the blood-brain barrier: a role for RMP-7 in brain tumor therapy.

The effect and mechanism of the blood-brain barrier-permeabilizing agent, RMP-7, was investigated in a series of studies employing a rat RG2 glioma model. Changes in uptake of carboplatin into brain tumor and various nontumor brain tissue regions was determined using a sophisticated image analysis system. This system permitted quantitative autoradiography to be analyzed simultaneously with overlayed histological images from the same coronal brain section. A wide range of intracarotid doses of RMP-7 (0.01 to 9.0 micrograms/kg) was shown to significantly increase the permeability of carboplatin into tumor tissue and surrounding brain tissue (up to twofold) in a dose-dependent manner. Additionally, substantially greater permeability effects were seen in the tumor compared to healthy brain. Moreover, a clear topographic profile was observed in nontumor brain tissue, with progressively less uptake observed with increasing distance from the tumor. The fact that RMP-7 increased the uptake of carboplatin into ipsilateral brain tissue outside the tumor mass has potential implications for treating human glioma patients, for it is commonly recognized that tumor cells typically migrate from the tumor mass into surrounding brain tissue thereby escaping conventional attempts to destroy the malignant cells. To help elucidate the mechanism of RMP-7's permeability effects, the uptake of carboplatin was also determined under conditions where either the bradykinin B2 receptor antagonist, HOE140, or the B1 antagonist, [desArg10]HOE140, was coadministered with RMP-7. Results indicate that RMP-7's effects are mediated specifically through bradykinin B2 receptors. Furthermore, neither bradykinin antagonist alone affected the uptake of carboplatin into the leaky tumor region, suggesting that abnormal elevations in endogenous bradykinin activity are not likely responsible for the characteristic leaky nature of the tumor vascular barrier. The combined results from these studies therefore offer new insight into the characteristics of the vascular barriers in normal and tumor brain tissue and further elucidate the novel permeability effects of RMP-7. Together, they support its potential use as an adjunctive therapy for the selective delivery of chemotherapeutic drugs to brain tumors and possibly other neurodegenerative conditions.

Delay of nomifensine-induced seizures by fusaric acid, alpha-methyltyrosine and haloperidol.

An In Vivo model is presented to determine the effects of alpha methyl-para-tyrosine methyl ester (MPT), fusaric acid (FA), and haloperidol on nomifensine-induced seizures. All three drugs were active with haloperidol having the greatest effect on delay of onset to convulsion. The results suggest that both dopamine and norepinephrine are involved in nomifensive-induced convulsions and that administering agents known to lower both dopamine and/or norepinepherine in the rat brain delays onset but that haloperidol, which specifically blocks post-synaptic dopamine receptors, had the greatest activity.

Preventing burnout: an alternative approach.

Burnout is a potentially serious dilemma which any practicing pharmacist may encounter. Various suggestions have been proposed to prevent burnout. An alternative approach is presented which involves the pharmacist in a nontraditional role. Pharmacists participate in a 3-month rotation within the Idaho Drug Information Service and Regional Poison Control Center. Pharmacists involved in this rotation believe it is extremely important for expanding their professional roles and preventing burnout.

Amitriptyline-related peripheral neuropathy relieved during pyridoxine hydrochloride administration.

Tricyclic antidepressants rarely cause peripheral neuropathy. In fact, this class of drugs has been used to control the symptoms of pain and paresthesia that accompany peripheral neuropathy. We report peripheral paresthesias that occurred in a 39-year-old female during five years of amitriptyline administration. The patient's symptoms were relieved by oral pyridoxine hydrochloride, associated with elevated plasma pyridoxal phosphate.