From blood to brain through BBB and astrocytic signaling

Need for a Paradigm Shift in the Treatment of Ischemic Stroke: The Blood-Brain Barrier

Blood-brain barrier (BBB) integrity is essential to maintaining brain health. Aging-related alterations could lead to chronic progressive leakiness of the BBB, which is directly correlated with cerebrovascular diseases. Indeed, the BBB breakdown during acute ischemic stroke is critical. It remains unclear, however, whether BBB dysfunction is one of the first events that leads to brain disease or a down-stream consequence. This review will focus on the BBB dysfunction associated with cerebrovascular disease. An added difficulty is its association with the deleterious or reparative effect, which depends on the stroke phase. We will first outline the BBB structure and function. Then, we will focus on the spatiotemporal chronic, slow, and progressive BBB alteration related to ischemic stroke. Finally, we will propose a new perspective on preventive therapeutic strategies associated with brain aging based on targeting specific components of the BBB. Understanding BBB age-evolutions will be beneficial for new drug development and the identification of the best performance window times. This could have a direct impact on clinical translation and personalised medicine.

Improving glioblastoma therapeutic outcomes via doxorubicin-loaded nanomicelles modified with borneol

Glioblastoma is a grade IV malignant glioma with high recurrence and metastasis and faces a therapeutic obstacle that the blood-brain barrier (BBB) severely hinders the brain entry and efficacy of therapeutic drugs. Previous studies suggest that borneol (BO) has been used to enhance interested drugs to penetrate the BBB. In this study, a borneol-modified nanomicelle delivery system was established to facilitate the brain entry of doxorubicin for glioblastoma therapy. Herein, we firstly conjugated borneol molecules with DSPE-PEG₂₀₀₀-COOH to synthesize a novel carrier DSPE-PEG₂₀₀₀-BO and also characterized its structure. Doxorubicin-loaded nanomicelles (DOX BO-PMs) were prepared using DSPE-PEG₂₀₀₀-BO via electrostatic interaction and the physicochemical properties were investigated. The average particle size and zeta potential of DOX BO-PMs were respectively (14.95 ± 0.17)nm and (-1.27 ± 0.06)mV, and the drug encapsulation efficiency and loading capacity in DOX BO-PMs were (95.69 ± 0.49)% and (14.62 ± 0.39)%, respectively. The drug release of the DOX BO-PMs exhibited a both time- and pH-dependent pattern. The results demonstrated that DOX BO-PMs significantly enhanced the transport efficiency of DOX across the BBB and also exhibited a quick accumulation in the brain tissues. The in vitro anti-proliferation assay results suggested that DOX BO-PMs exerted a strong inhibitory effect on proliferation of glioblastoma cells. Importantly, in vivo antitumor results demonstrated that DOX BO-PMs significantly inhibited the tumor growth and metastasis of glioblastoma. In conclusion, DOX BO-PMs can improve the glioblastoma therapeutic outcomes and become a promising nanodrug candidate for the application of doxorubicin in the field of glioblastoma therapy.

Regulation of plasma agouti-related protein and its relationship with hunger in lean and obese men

Agouti-related protein (AgRP) is an orexigenic (appetite stimulating) neuropeptide suggested to exert tonic control over long-term energy balance. While some have speculated AgRP is not involved in the episodic (i.e. meal to meal energy intake) control, acute decreases in plasma agouti-related protein (AgRP) following a meal have been observed in humans in a role consistent with episodic control for AgRP. Whether changes in plasma AgRP are associated with episodic, and/or tonic changes in appetite has yet to be directly examined. The present study examined the relationship between agouti-related protein (AgRP), leptin and the regulation of appetite following a 48-h fast and an acute meal challenge. Blood samples were obtained from young lean and obese men before and after a 48 h fast (lean n = 10; obese n = 7). Fasting resulted in an increase in AgRP and a decrease in leptin with these changes being greater in lean than obese. In addition, blood samples were obtained from lean men before and 1, 2, 3 and 4 h after a meal (n = 8). Following a meal, AgRP was reduced from 2 to 4 h, a change that was dissociated from both leptin and subjective measures of hunger and satiety. These results demonstrate that AgRP is not associated with changes in hunger or satiety, and can change without corresponding changes in leptin. This suggests that AgRP may not be involved in the episodic control of appetite and the release of AgRP may involve signals other than leptin.