Biology subjects

Bajracharya, R.

Publications and source records attributed to Bajracharya, R..

3 recordsLinked to original sources

bioRxiv2025

Caspase-1 self-terminates protease activity to enforce homeostasis and prevent inflammasome-driven diseases

Signal shutdown mechanisms must exist to silence the potent inflammatory programs initiated by the caspase-1 (CASP1) protease, to allow inflammation to resolve and reinstate tissue homeostasis. It is unknown how CASP1 terminates its activity in vivo. Here, we use a knock-in mouse model in which the CASP1 CARD domain linker (CDL) is mutated to prevent self-cleavage (Casp1.CDL mice) to show that CASP1 CDL autoproteolysis terminates CASP1 activity in vivo. We examined these mice under homeostatic conditions and in response to major physiological challenges. In the brain, CASP1 CDL mutation caused anxiety-like behaviour under homeostatic conditions, and exacerbated hippocampal spatial learning deficits in the APP23 genetic model of amyloid-induced neurodegeneration. In the bone marrow, CASP1 CDL mutation promoted steady-state granulopoiesis. In a model of diet-induced liver disease, CASP1 CDL mutation accelerated liver steatosis and promoted liver immune cell infiltration, inflammation and damage. In a liver healing model, CASP1 CDL mutation delayed disease resolution, indicating that CASP1 autocleavage is required to restore homeostasis after a major challenge to organ function. Our data reveal that CASP1 CDL self-cleavage terminates CASP1 inflammatory programs in vivo to maintain homeostasis in steady-state, restore homeostasis after a major challenge to organ function, and suppress inflammasome-driven diseases. These data identify CASP1 as a prime anti-inflammatory drug target, as CASP1 inhibitors may enforce homeostasis and prevent inflammasome-driven diseases.

immunology↗

bioRxiv2023

Increased tau expression in the APOE4 blood-brain barrier model is associated with reduced anti-tau therapeutic antibody delivery in vitro.

Tau protein is a critical driver of neurodegeneration and an important drug target in Alzheimers disease (AD). Tau-specific immunotherapy has emerged as a promising treatment strategy for AD, however the therapeutic efficacy of anti-tau antibodies may be limited by their insufficient delivery across the blood-brain barrier (BBB). The apolipoprotein E4 allele (APOE4) is the strongest genetic risk factor for sporadic AD and is known to influence tau-mediated neurodegeneration. Interestingly, both tau and APOE4 have been implicated in the cerebrovascular pathology observed in AD. Yet, the crosstalk between APOE4 and tau at the level of the BBB and its consequences for anti-tau immunotherapeutics delivery, remain poorly understood. Here, we utilised APOE3- and APOE4-carrying human iPSC-derived induced brain endothelial-like cells (iBECs) as a sporadic AD BBB model, determined the levels of endogenous tau in iBECs, and explored the transport of two novel monoclonal anti-tau antibodies, RNF5 and RN2N, across the in vitro barrier. Our results demonstrate that MAPT gene transcription, tau protein levels and tau phosphorylation are increased in iBECs in an APOE4-related manner and are associated with reduced iBEC monolayer integrity and increased permeability to biologically inert fluorescent tracers. Additionally, elevated levels of intracellular tau in APOE4 cells were accompanied by the reduced passive permeability of therapeutic anti-tau antibodies through the APOE4 iBEC monolayer, which could be improved by the application of focused ultrasound and microbubble drug-delivery technology. Together, our study illustrates a new role for APOE4 and tau in human iBECs with potential implications for BBB dysfunction and anti-tau therapeutic antibody delivery.

cell biology↗

bioRxiv2021

Ultrasound-mediated delivery of novel tau-specific monoclonal antibody enhances brain uptake but not therapeutic efficacy

Tau-specific immunotherapy is an attractive therapeutic strategy for the treatment of Alzheimers disease and other tauopathies. However, targeting tau effectively remains a considerable challenge due to the restrictive nature of the blood-brain barrier (BBB), which excludes 99.9% of peripherally administered antibodies. We have previously shown that the delivery of tau-specific monoclonal antibody (mAb) with low-intensity scanning ultrasound in combination with intravenously injected microbubbles (SUS+MB) increases the passage of IgG antibodies into the brain. SUS+MB transiently opens tight junctions to allow paracellular transport, but also facilitates transcellular transport, particularly for larger cargoes. However, therapeutic efficacy after enhanced brain delivery has not been explored. To assess whether ultrasound-mediated delivery of tau-specific mAbs leads to an enhanced therapeutic response, K369I tau transgenic K3 mice were passively immunised once weekly for 12 weeks with a novel mAb, RNF5, in combination with SUS+MB. While none of the treatment arms improved behaviour or motor functions in these mice, we found that both RNF5 and SUS+MB treatments on their own reduced tau pathology, but, surprisingly, the combination of both (RNF5+SUS+MB) did not achieve an additive reduction in tau pathology. This was despite observing increased antibody penetration in the brain. Interestingly, a significant fraction of the antibody in the combination treatment was visualized in brain endothelial cells, suggesting that paracellular transport may not be the preferred uptake mechanism for RNF5. Taken altogether, more research is warranted to develop SUS+MB as a delivery modality for anti-tau antibodies.

neuroscience↗