A simple novel approach for detecting blood-brain barrier permeability using GPCR internalization.

AIMS: Impairment of blood-brain barrier (BBB) is involved in numerous neurological diseases from developmental to aging stages. Reliable imaging of increased BBB permeability is therefore crucial for basic research and preclinical studies. Today, the analysis of extravasation of exogenous dyes is the principal method to study BBB leakage. However, these procedures are challenging to apply in pups and embryos and may appear difficult to interpret. Here we introduce a novel approach based on agonist-induced internalization of a neuronal G protein-coupled receptor widely distributed in the mammalian brain, the somatostatin receptor type 2 (SST2). METHODS: The clinically approved SST2 agonist octreotide (1 kDa), when injected intraperitoneally does not cross an intact BBB. At sites of BBB permeability, however, OCT extravasates and induces SST2 internalization from the neuronal membrane into perinuclear compartments. This allows an unambiguous localization of increased BBB permeability by classical immunohistochemical procedures using specific antibodies against the receptor. RESULTS: We first validated our approach in sensory circumventricular organs which display permissive vascular permeability. Through SST2 internalization, we next monitored BBB opening induced by magnetic resonance imaging-guided focused ultrasound in murine cerebral cortex. Finally, we proved that after intraperitoneal agonist injection in pregnant mice, SST2 receptor internalization permits analysis of BBB integrity in embryos during brain development. CONCLUSIONS: This approach provides an alternative and simple manner to assess BBB dysfunction and development in different physiological and pathological conditions.

Off-label use of drugs in pain medicine and palliative care: an algorithm for the assessment of its safe and legal prescription.

Off-label medication use is common practice, particularly in difficult to treat patients who have already tried commonly accepted medication unsuccessfully. Health authorities try to regulate this practice to protect the patient's safety and to prevent over consumption of new and more expensive drugs. Justified off-label drug use requires a thorough assessment. Physicians, in cooperation with formulary committees, need tools to structure this assessment. The evaluation algorithm for off-label prescription we present here, to be used after identification of a planned off-label application, consists of four steps. Step 1 indicates the extent of the problem and the need for further investigation. Step 2 is the decisional process evaluating the necessity of off-label use in identified prescriptions and confirmation as to what extent it needs further investigation. In step 3, the scientific knowledge to support the proposed off-label use is gathered in a short or extensive evaluation trajectory. The short trajectory consists of assembling the information approved in other countries or in accepted guidelines and textbooks, whereas the extensive trajectory is necessary when the indication, route, or formulation is not approved nationally or internationally. Assessment needs to be based on a literature research on the clinical and pharmacological information of the product. Step 4 is the acceptance or rejection of the off-label use of the drug for the indication at hand. Those four steps need to be carefully documented. Treatment outcome will then be closely monitored, documented, and made available to professionals, thus allowing for regular update of recommendations. This algorithm can help formulary committees to develop a strategy for evaluating off-label prescriptions in well-defined conditions, and help healthcare providers to develop protocols and guidelines.