Small Molecule Amyloid-β Protein Precursor Processing Modulators Lower Amyloid-β Peptide Levels via cKit Signaling

Alzheimer's disease (AD) is characterized by the accumulation of neurotoxic amyloid-β (Aβ) peptides consisting of 39-43 amino acids, proteolytically derived fragments of the amyloid-β protein precursor (AβPP), and the accumulation of the hyperphosphorylated microtubule-associated protein tau. Inhibiting Aβ production may reduce neurodegeneration and cognitive dysfunction associated with AD. We have previously used an AβPP-firefly luciferase enzyme complementation assay to conduct a high throughput screen of a compound library for inhibitors of AβPP dimerization, and identified a compound that reduces Aβ levels. In the present study, we have identified an analog, compound Y10, which also reduced Aβ. Initial kinase profiling assays identified the receptor tyrosine kinase cKit as a putative Y10 target. To elucidate the precise mechanism involved, AβPP phosphorylation was examined by IP-western blotting. We found that Y10 inhibits cKit phosphorylation and increases AβPP phosphorylation mainly on tyrosine residue Y743, according to AβPP751 numbering. A known cKit inhibitor and siRNA specific to cKit were also found to increase AβPP phosphorylation and lower Aβ levels. We also investigated a cKit downstream signaling molecule, the Shp2 phosphatase, and found that known Shp2 inhibitors and siRNA specific to Shp2 also increase AβPP phosphorylation, suggesting that the cKit signaling pathway is also involved in AβPP phosphorylation and Aβ production. We further found that inhibitors of both cKit and Shp2 enhance AβPP surface localization. Thus, regulation of AβPP phosphorylation by small molecules should be considered as a novel therapeutic intervention for AD.

Neurovascular Complications of Acute Aortic Syndrome

Acute aortic syndromes (AAS) such as aortic dissection, intramural hematoma, and penetrating aortic ulcer pose significant neurovascular risks, affecting patient outcomes. This review examines the incidence, clinical presentation, and outcomes of neurovascular complications in AAS patients. Common complications include stroke, spinal cord ischemia, and transient ischemic attacks, with stroke being the most prevalent. Managing aortic dissection necessitates careful blood pressure control to prevent dissection progression while avoiding compromised cerebral and spinal perfusion. Carotid involvement, particularly dissection, increases stroke and transient ischemic attack risks. Emergency surgical interventions, though essential to prevent rupture or repair dissection, carry risks of perioperative neurovascular complications. The use of electroencephalography and transcranial Doppler can aid in the early detection and monitoring of neurovascular events. We discuss the pros and cons of certain blood pressure medications in the acute treatment of aortic dissection. A multidisciplinary approach involving cardiovascular surgeons, neurologists, and critical care specialists is vital for optimizing outcomes and mitigating risks. Early recognition and management of neurovascular complications are crucial, and further research is needed to develop targeted prevention and treatment strategies.

Stabilizing breathing pattern using local mechanical vibrations: comparison of deterministic and stochastic stimulations in rodent models of apnea of prematurity

Mechanical stimulation has been shown to reduce apnea of prematurity (AOP), a major concern in preterm infants. Previous work suggested that the underlying mechanism is stochastic resonance, amplification of a subthreshold signal by stochastic stimulation. We hypothesized that the mechanism behind the reduction of apnea length may not be a solely stochastic phenomenon, and suggest that a purely deterministic, non-random mechanical stimulation could be equally as effective. Mice and rats were anesthetized, tracheostomized, and mechanically ventilated to halt spontaneous breathing. Two miniature motors controlled by a microcontroller were attached around the abdomen. Ventilation was paused, stimulations were applied, and the time to the rodent's first spontaneous breath (T) was measured. Six spectrally different signals were compared to one another and the no-stimulation control in mice. The most successful deterministic stimulation (D) at reducing apnea was then compared to a pseudo-random noise (PRN) signal of comparable amplitude and frequency. CO2%, CO2 stabilization time (Ts), O2 saturation (SpO2%), and T were also measured. D significantly reduced T compared to no stimulation for medium and high amplitudes. PRN also reduced T, without  a difference between D and PRN. Furthermore, both stimulations significantly reduced Ts with no significant differences between the respective stimulations. However, there was no effect of D or PRN on SpO2%. The lack of differences between D and PRN led to an additional series of experiment comparing the same D to a band-limited white noise (WN) signal in young rats. Both D and WN were shown to significantly reduce T, with D showing statistical superiority in reduction of apnea. We further speculate that both deterministic and stochastic mechanical stimulations induce some form of mechanotransduction which is responsible for their efficacy, and our findings suggest that mechanical stimulation may be effective in treating AOP.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13534-021-00203-x.