Blood-Brain-Barrier (BBB) Targeting Nanoparticulate Drug Delivery Modules to Treat Cerebrovascular Disorders: Current State of the Art

Testing of a hypothesis for osmotic opening of the blood-brain barrier.

Background: Diabetes Mellitus is a worldwide disease that leads to several acute complications including diabetic ketoacidosis. Diabetic ketoacidosis is usually preceded by infection, acute myocardial infarction, stroke, or other dire events. There is one report where diabetic ketoacidosis was reported to be associated with acute arterial embolism. Acute arterial thrombosis is a rare disease that requires immediate treatment. Methods: We present a diabetic patient who presented with acute arterial embolism and developed diabetic ketoacidosis. This is the first case in our hospital in which we have reported with acute brachial artery thrombosis and DKA. Results: We present a 68 years old male chronic smoker with a 25 year history of type 2 Diabetes (non-compliant to medications), Peripheral vascular disease, dyslipidemia and transient ischemic attack. He experienced severe pain and numbness in his right arm and forearm with no wound, puncture lesion or ecchymosis. Forearm was cold, pale with delayed capillary refill on right hand. Right brachial, right radial and right ulnar arteries were not palpable. Strong pulsations of the right subclavicular and right carotid arteries were palpated. This led to a strong suspicion of an acute thrombosis of the right brachial artery. Emergency thrombectomy with +/ − fasciotomy was planned. Patient was anticoagulated with intravenous heparin. Patient's blood sugar was persistently elevated and blood gases showed mild acidosis. Urinary examination confirmed presence of diabetic ketoacidosis. Conclusions: A high index of suspicion of diabetic ketoacidosis in patients with acute arterial thrombosis may lead to early recognition and treatment, avoiding any adverse outcome.

Management of acute infrainguinal arterial thrombosis: combined intraoperative balloon thrombectomy with balloon angioplasty: a preliminary report.

FLZ, a novel anti-Parkinson's disease (PD) candidate drug, has shown poor blood-brain barrier (BBB) penetration based on the pharmacokinetic study using rat brain. P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) are two important transporters obstructing substrates entry into the CNS as well as in relation to PD neuropathology. However, it is unclear whether P-gp and BCRP are involved in low BBB permeability of FLZ and what the differences of FLZ brain penetration are between normal and Parkinson's conditions. For this purpose, in vitro BBB models mimicking physiological and PD pathological-related BBB properties were constructed by C6 astroglial cells co-cultured with primary normal or PD rat cerebral microvessel endothelial cells (rCMECs) and in vitro permeability experiments of FLZ were carried out. High transepithelial electrical resistance (TEER) and low permeability for sodium fluorescein (NaF) confirmed the BBB functionality of the two models. Significantly greater expressions of P-gp and BCRP were detected in PD rCMECs associated with the lower in vitro BBB permeability of FLZ in pathological BBB model compared with physiological model. In transport studies only P-gp blocker effectively inhibited the efflux of FLZ, which was consistent with the in vivo permeability data. This result was also confirmed by ATPase assays, suggesting FLZ is a substrate for P-gp but not BCRP. The present study first established in vitro BBB models reproducing PD-related changes of BBB functions in vivo and demonstrated that poor brain penetration of FLZ and low BBB permeability were due to the P-gp transport.

The objective of this study was to evaluate the immediate efficacy and long-term results of a standard protocol of percutaneous, low dose, intraarterial streptokinase treatment in acute arterial thrombosis. This involved analysis of 48 consecutive patients with acute peripheral arterial thrombosis, treated with thrombolysis between October 1988 and August 1997. There were 30 men and 18 women patients, with an average age of 66.5 years. There was thrombosis of the native artery in 32, thrombosis of an aneurysm in seven, and graft occlusion in nine. After the occlusion was defined by arteriography, the low-dose streptokinase (10,000 units per hour) was continuously infused into the thrombosed segment following a bolus injection of 10,000 units. The initial success rate (defined as partial or complete lysis) was 79.6%. Additional therapy after lysis consisted of percutaneous transluminal angioplasty in 18, bypass surgery in six, anticoagulant therapy in seven, and amputation in seven owing to irreversible ischemic damage. One patient died of myocardial infarction before additional therapy. Of the 20.4% failures to fibrinolysis, two patients received bypass surgery, two surgical thrombectomy, three sympathectomy, and three had amputations. Local bleeding complications were seen in five (10%) patients. Only one patient needed surgical exploration. Allergic reaction to streptokinase was seen in five patients (10%) and fibrinolytic therapy was continued with urokinase in three. In the follow-up (1-107 months) eight patients died and three amputations were performed after a mean time of 17 months after thrombolysis owing to progression of arteriosclerosis. This resulted in a limb salvage rate of 76% after 1 year and 65% after 5 years (Kaplan-Meier). Low-dose, local, intraarterial streptokinase therapy is an effective preliminary step in management of acute arterial thrombosis. Especially with adequate additional treatment, it is possible to achieve satisfactory long-term patency rates.

Acute upper extremity arterial thrombosis and stroke in an unresected pheochromocytoma

BackgroundAcute iliac arterial thrombosis during surgery is very rare complication. There were few reports on this complication relative to gastroenterological surgery, and the risk has not been recognized.Case presentationA 70-year-old man, diagnosed with a rectal cancer (adenocarcinoma of rectum) with known history heavy cigarette smoking with no known history of peripheral vascular disease underwent a laparoscopic abdominoperineal resection. He presented severe pain in the left leg in the recovery room. A computed tomography (CT) scan revealed the complete obstruction of the left common iliac artery. A successful revasculization was achieved through a thrombotectomy and percutaneous transluminal angioplasty with a stent immediately after the diagnosis. The pain in the left leg disappeared immediately after the revasculization.ConclusionAn acute arterial thrombosis is a potential complication of the laparoscopic colorectal surgery with the lithotomy position.

AT THE END OF THE CENTURY before the last, a young graduate student performed an experiment that would forever change the way we look at the microvasculature of the brain. He injected basic dyes into the blood and noted that nearly every tissue of the body was colored by the dye except for the central nervous system (CNS). This experiment and the observation that bile salts could cause seizures when injected into the brain but not intravenously were the seminal 19th century observations giving rise to the concept of a blood-brain barrier (BBB). The young graduate student, Paul Ehrlich, would get many things right in his career, winning a Nobel prize in 1908 for his work on antibiotics. But the BBB he got wrong. Ehrlich thought the brain did not stain because the dye was not taken up by brain tissue, not because a barrier prevented the dye from reaching the brain. Indeed, that a BBB really existed and that it resided at the level of the capillary bed and the choroid plexus were not finally established until the late 1960s. Elegant physiological experiments by Davson and Segal (10) and electron microscopy studies by Reese and Karnovsky (24) demonstrated the basis of the BBB: the capillary bed of adult mammals is modified to exclude the production of a plasma ultrafiltrate. The major modifications include a greatly decreased rate of pinocytosis, a lack of intracellular pores and fenestrae, and obliteration of the intercellular space between brain endothelial cells by tight junctions that essentially “cement” apposing endothelial cells together. The lack of production of an ultrafiltrate means that circulating proteins such as albumin do not exude from blood into brain. This is the basis for Ehrlich’s 120-year-old observation: basic dyes bind to albumin so tightly that they are a visible proxy for plasma

BACKGROUND: A major challenge in the treatment of brain tumors is the limited penetration of many drugs through the blood-brain barrier (BBB). BBB characteristics include endothelial cells connected by tight junction proteins (e.g. Claudin5) and expression of efflux transporters (e.g.P-gp) with the physiological role to limit the accumulation of potentially toxic substances in brain tissue. While BBB permeability shows anatomical region-specific characteristics and changes with age, brain tumors can also impact its integrity. To achieve therapeutically relevant drug concentrations in the tumor, characterization of the pathophysiological BBB is fundamental when developing (pre)clinical trials. Our study seeks to increase our understanding of the BBB composition in various molecular groups of ependymoma. RESULTS: Transcriptional BBB characteristics were assessed for primary ependymoma (n=440), cell lines (n=3), mouse models (n=22), and healthy brain controls (n=200). T-distributed stochastic neighbor embedding (tSNE)-based clustering analyses based on most relevant tight junction and efflux transporter gene sets revealed distinct molecular ependymoma group-specific expression patterns. While patient-derived xenografts models (PDX, n=20) showed high similarity with patient tumor samples, in utero electroporation-based (IUE, n=2) mouse models did not fully recapitulate these BBB characteristics. Supratentorial ependymoma with ZFTA fusions revealed a higher transcriptional expression level of important tight junctions (e.g.Claudin5) compared to other groups and normal brain which was confirmed at protein level in respective PDX models by using both western blot and ultra-high content imaging. CONCLUSION: Analyses of important BBB markers revealed significant differences between molecular groups of ependymoma, which may partly explain drug resistance of ependymoma with ZFTA fusion caused by a low BBB permeability. BBB characteristics of corresponding models suggest that IUE and PDX models representing ZFTA fusion-driven tumors cannot equally be used within preclinical drug trials. Findings will be further validated in preclinical studies while molecular BBB characterization will be expanded to other brain tumors.

The blood-brain barrier (BBB) is an active interface between the circulation and the central nervous system (CNS) with a dual function: the barrier function restricts the transport from the blood to the brain of potentially toxic or harmful substances; the carrier function is responsible for the transport of nutrients to the brain and removal of metabolites. The BBB plays a crucial role in the clinical practice as well. On the one side there is a large number of neurological disorders including cerebral ischemia, brain trauma and tumors, neurodegenerative disorders, in which the permeability of the BBB is increased. On the other hand due to the relative impermeability of the barrier many drugs are unable to reach the CNS in therapeutically relevant concentration, making the BBB one of the major impediments in the treatment of CNS disorders. The significant scientific and industrial interest in the physiology and pathology of the BBB led to the development of several in vitro models of the BBB. These models are mainly based on the culture of cerebral endothelial cells. The best in vitro models which mimic the best way the in vivo anatomical conditions are the co-culture models in which brain endothelial cells are co-cultured with astrocytes and/or pericytes. Our in vitro BBB model is characterized by high transendothelial electrical resistance (TEER regularily above 200 Ohm x cm(2)), low permeability and expression of several transporters. Our experiments have proven that the model is suitable for basic research and for testing the interaction between the BBB and potential drug candidates (toxicity, permeability, interaction with efflux transporters) as well.

PP217—Correlation between in vitro tests for blood brain barrier penetration with in vivo gliclazide penetration

Objective To investigate the dynamic changes of blood-brain barrier(BBB) permeability after acute cerebral ischemia in rats with middle cerebral artery occlusion (MCAO) by dynamic contrast-enhanced(DCE)-MRI. Methods Sixty MCAO rat models were established by suture-occlusion method. All rats were divided randomly into twelve groups with different ischemia duration (3 hours, 6 hours, permanent) and reperfusion times (2, 6, 12 and 24 hours after reperfusion). Each group was examined by MRI at the time points. The BBB permeability parameters(Ktrans, Ve, Kep, rKtrans, rVe, rKep) were calculated by Siemens workstation and compared with Evans blue(EB) extravasation results. Multivariate analysis of variance (M-ANOVA), one-way analysis of variance (one-way ANOVA), Pearson analysis were respectively used to verify the influences of ischemia duration and reperfusion time on BBB permeability parameters, EB extravasation and relationships between parameters. Results In 3 hours and 6 hours ischemia duration groups, change of BBB permeability after reperfusion appeared biphasic. At 2 hours and 6 hours after reperfusion, BBB permeability increased, while rKtrans values and rVe values rose and rKep values dropped. BBB permeability decreased at 12 hours and increased again at 24 hours after reperfusion. The highest BBB permeability was observed at 6 hours after reperfusion. However, BBB permeability in permanent ischemia groups had uniphasic change, as its increase was rather mild as ischemia time went on. rKtrans values(1.99±0.79)were positively correlated with rVe values(2.88±1.78)(r=0.93, P<0.01) and negatively correlated with rKep values(0.66±0.21)(r=-0.84, P<0.01). The negative correlation between rVe values and rKep valueswas also significant(r=-0.80, P<0.01). EB extravasation results were consistent with MRI findings. Conclusions BBB permeability change was biphasic in reperfusion groups, while it was uniphasic in permanent ischemia groups. DCE-MRI may accurately reflect the changes of BBB permeability after acute cerebral ischemia. Both ischemic duration and reperfusion time had influences on BBB permeability. With prolongation of ischemic time, the duration of BBB permeability increase became shorter, BBB damage appeared earlier, with increased degree of ischemic damage. Key words: Blood brain barrier; Reperfusion injury; Infarction, middle cerebral artery; Magnetic resonance imging

Existing drug delivery methods have not led to a significant increase in survival for patients with malignant primary brain tumors. While the combination of conventional therapies consisting of surgery, radiotherapy, and chemotherapy has improved survival for some types of brain tumors (e.g., WNT medulloblastoma), other types of brain tumors (e.g., glioblastoma and diffuse midline glioma) still have a poor prognosis. The reason for the differences in response can be largely attributed to the blood–brain barrier (BBB), a specialized structure at the microvasculature level that regulates the transport of molecules across the blood vessels into the brain parenchyma. This structure hampers the delivery of most chemotherapeutic agents for the treatment of primary brain tumors. Several drug delivery methods such as nanoparticles, convection enhanced delivery, focused ultrasound, intranasal delivery, and intra-arterial delivery have been developed to overcome the BBB in primary brain tumors. However, prognosis of most primary brain tumors still remains poor. The heterogeneity of the BBB in primary brain tumors and the distinct vasculature of tumors make it difficult to design a drug delivery method that targets the entire tumor. Drug delivery methods that combine strategies such as focused ultrasound and nanoparticles might be a more successful approach. However, more research is needed to optimize and develop new drug delivery techniques to improve survival of patients with primary brain tumors.

To analyze the surgical treatment and prognosis of non-traumatic acute lower limb ischemia, and compare the morbidity and prognosis of acute arterial embolism and acute arterial thrombosis. The clinical data of 154 acute lower limb ischemia patients surgically treated from July 1999 to December 2007 were retrospectively analyzed. Fogarty catheter embolectomy was used in all patients; in which, 128 cases underwent Fogarty catheter embolectomy only, 8 cases Fogarty catheter embolectomy combined with endarterectomy, 13 cases Fogarty catheter embolectomy combined with vascular reconstruction with prosthetic graft or great saphenous vein, 5 cases Fogarty catheter embolectomy combined with amputation. The patients were divided into two groups according to pathogenesis: acute arterial embolism group (99 cases) and acute arterial thrombosis group (55 cases). The morbidity, amputation, perioperative mortality rates and high risk factors of amputation in the two groups were compared. Female experienced acute arterial embolism more often than man (60.6% vs 39.4%, P < 0.05), and more acute arterial thrombosis occurred in man (72.7% vs 27.3%, P < 0.05). The amputation rate of all cases was 9.7%, and perioperative mortality rate was 11.7%. The amputation rate in acute arterial embolism group was lower than acute arterial thrombosis group (5.1% vs 18.2%, P < 0.05). The perioperative mortality rates in the two groups were equal (11.1% vs 12.7%, P > 0.05). The statistically high risk factor of amputation for two groups was ischemic time, and smoking and diabetes were high risk factors for acute arterial thrombosis. Men experiences acute arterial thrombosis more often, and women experiences acute arterial embolism more often. The amputation rate of acute arterial embolism is lower than acute arterial thrombosis, and acute arterial thrombosis has more high risk factors of amputation.

Photodynamic therapy (PDT), a minimally invasive therapeutic tool, has been an important option for post-surgical treatment of malignant gliomas (MGs) in both adult and young patients. Recent studies have shown that PDT can also open the blood-brain barrier (BBB). However, there are no optimized parameters of PDT for patients at different ages. To determine whether there are age differences in PDT effects on the BBB, we studied PDT-related BBB opening through the optical clearing skull window in healthy 4- and 8-week-old mice. In this work, we realized BBB opening by combining PDT with the optical clearing skull window by using different radiant exposures (635 nm, 10-20-30-40 J/cm2 ) and 5-aminole-vulinic acid (5-ALA, 20 mg/kg). Then, we evaluated BBB permeability by: (i) spectrofluorimetric measuring of Evans Blue dye (EBd) leakage; (ii) confocal imaging of 70 kDa FITC-dextran extravasation and the BBB integrity; and (iii) histological analysis of brain tissues. Using the skull optical clearing method, we demonstrated PDT-induced BBB opening to EBd and FITC-dextran in a radiant exposure manner. The histological analysis revealed the different severities of vasogenic edema corresponding to radiant exposures. Besides, the PDT-related increase in the BBB permeability to high weight molecules (EBd and FITC-dextran) and solutes (vasogenic edema) was more pronounced in 4-week-old mice than in 8-week-old mice. The more pronounced PDT-induced BBB disruption in juvenile mice compared with adult mice suggests age differences in PDT-related BBB opening. This might be an important informative platform for a new application of PDT as a method for brain drug delivery, especially for post-surgical treatment of MGs. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.