The gut microbiota is now well known to affect the host’s immune system. One way of bacterial communication with host cells is via the secretion of vesicles, small membrane structures containing various cargo. Research on vesicles secreted by Gram-positive gut bacteria, their mechanisms of interaction with the host and their immune-modulatory effects are still relatively scarce. Here we characterized the size, protein content, and immune-modulatory effects of extracellular vesicles (EVs) secreted by a newly sequenced Gram-positive human gut symbiont strain - Bifidobacterium longum AO44. We found that B. longum EVs exert anti-inflammatory effects, inducing IL-10 secretion from both splenocytes and dendritic cells (DC)-CD4+ T cells co-cultures. Furthermore, the EVs protein content showed enrichment in ABC transporters, quorum sensing proteins, and extracellular solute-binding proteins, which were previously shown to have a prominent function in the anti-inflammatory effect of other strains of B. longum. This study underlines the importance of bacterial vesicles in facilitating the gut bacterial immune-modulatory effects on the host and sheds light on bacterial vesicles as future therapeutics.

ApolipoproteinE4 (apoE4) is the most prevalent genetic risk factor for Alzheimer’s disease (AD) and as such is a promising therapeutic target. This study examined the extent to which the pathological effects of apoE4 can be counteracted in vivo utilizing an immunological approach in which anti-apoE4 antibodies are applied peripherally by i.p. injections into apoE4-targeted replacement mice. Prerequisites for the successful pursuit of this objective are the availability of antibodies that specifically bind brain apoE4 and not apoE3, and demonstrating that direct application of these antibodies into the brain can counteract the effects of apoE4. Accordingly, it was shown that the anti-apoE4 monoclonal antibody (mAb) 9D11 binds specifically to brain apoE4 and not apoE3. Direct i.c.v. application of mAb 9D11 prevented the apoE4-driven accumulation of Aβ in hippocampal neurons following activation of the amyloid cascade by inhibiting the Aβ-degrading enzyme neprilysin. These findings provide a proof-of-concept that anti-apoE4 mAb 9D11, when introduced into the brain, can counteract the apoE4 effects in vivo. Subsequent experiments, utilizing repeated i.p. injections of mAb 9D11, resulted in the formation of apoE/IgG complexes specifically in apoE4 mice. This was associated with reversal of the cognitive impairments of apoE4 in the Morris water maze and the novel object recognition test as well as with reversal of key apoE4-driven pathologies including the hyperphosphorylated tau and the reduced levels of the apoER2 receptor. These results indicate that anti-apoE4 immunotherapy counteracts the cognitive and brain pathological effects of apoE4, and suggest that such an approach could also benefit human apoE4 carriers.

Apolipoprotein E4 (ApoE4), the most prevalent genetic risk factor for Alzheimer’s disease (AD), is associated with increased neurodegeneration and vascular impairments. Vascular endothelial growth factor (VEGF), originally described as a key angiogenic factor, has recently been shown to play a crucial role in the nervous system. The objective of this research is to examine the role of VEGF in mediating the apoE4-driven pathologies. We show that hippocampal VEGF levels are lower in apoE4 targeted replacement mice compared to the corresponding apoE3 mice. This effect was accompanied by a specific decrease in both VEGF receptor-2 and HIF1- α . We next set to examine whether upregulation of VEGF can reverse apoE4-driven pathologies, namely the accumulation of hyperphosphorylated tau (AT8) and Aβ ₄₂ , and reduced levels of the pre-synaptic marker, VGluT1, and of the ApoE receptor, ApoER2. This was first performed utilizing intra-hippocampal injection of VEGF-expressing-lentivirus (LV-VEGF). This revealed that LV-VEGF treatment reversed the apoE4-driven cognitive deficits and synaptic pathologies. The levels of Aβ ₄₂ and AT8, however, were increased in apoE3 mice, masking any potential effects of this treatment on the apoE4 mice. Follow-up experiments utilizing VEGF-expressing adeno-associated-virus (AAV-VEGF), which expresses VEGF specifically under the GFAP astrocytic promoter, prevented this effects on apoE3 mice, and reversed the apoE4-related increase in Aβ ₄₂ and AT8. Taken together, these results suggest that apoE4-driven pathologies are mediated by a VEGF-dependent pathway, resulting in cognitive impairments and brain pathology. These animal model findings suggest that the VEGF system is a promising target for the treatment of apoE4 carriers in AD.

Extracellular vesicles (EVs) shed by cancer cells play a major role in mediating the transfer of molecular information by reprogramming the tumor microenvironment (TME). TP53 (encoding the p53 protein) is the most mutated gene across many cancer types. Mutations in TP53 not only result in the loss of its tumor-suppressive properties but also results in the acquisition of novel gain-of-functions (GOF) that promote the growth of cancer cells. Here, we demonstrate that GOF mutant p53 proteins can be transferred via EVs to neighboring cancer cells and to macrophages, thus modulating them to release tumor supportive cytokines. Our data from pancreatic, lung, and colon carcinoma cell lines demonstrate that the mutant p53 protein can be selectively sorted into EVs. More specifically, mutant p53 proteins in EVs can be taken up by neighboring cells and mutant p53 expression is found in non-tumor cells in both human cancers and in non-human tissues in human xenografts. Our findings shed light on the intricate methods in which specific GOF p53 mutants can promote oncogenic mechanisms by reprogramming and then recruiting non-cancerous elements for tumor progression.

Radiation therapy (RT) remains a common treatment for cancer patients worldwide, despite the development of targeted biological compounds and immunotherapeutic drugs. The challenge in RT lies in delivering a lethal dose to the cancerous site while sparing the surrounding healthy tissues. Low linear energy transfer (low-LET) and high linear energy transfer (high-LET) radiations have distinct effects on cells. High-LET radiation, such as alpha particles, induces clustered DNA double-strand breaks (DSBs), potentially inducing cell death more effectively. However, due to limited range, alpha-particle therapies have been restricted. In human cancer, mutations in TP53 (encoding for the p53 tumor suppressor) are the most common genetic alteration. It was previously reported that cells carrying wild-type (WT) p53 exhibit accelerated senescence and significant rates of apoptosis in response to RT, whereas cells harboring mutant p53 (mutp53) do not. This study investigated the combination of the alpha-emitting atoms RT based on internal Radium-224 (²²⁴Ra) sources and systemic APR-246 (a p53 reactivating compound) to treat tumors with mutant p53. Cellular models of colorectal cancer (CRC) or pancreatic ductal adenocarcinoma (PDAC) harboring mutant p53, were exposed to alpha particles, and tumor xenografts with mutant p53 were treated using²²⁴Ra source and APR-246. Effects on cell survival and tumor growth, were assessed. The spread of alpha emitters in tumors was also evaluated as well as the spatial distribution of apoptosis within the treated tumors. We show that mutant p53 cancer cells exhibit radio-sensitivity to alpha particles in vitro and to alpha-particles-based RT in vivo. APR-246 treatment enhanced sensitivity to alpha radiation, leading to reduced tumor growth and increased rates of tumor eradication. Combining alpha-particles-based RT with p53 restoration via APR-246 triggered cell death, resulting in improved therapeutic outcomes. Further preclinical and clinical studies are needed to provide a promising approach for improving treatment outcomes in patients with mutant p53 tumors.

Introduction Alzheimer's disease (AD) and synucleinopathies share common pathological mechanisms. Apolipoprotein E4 (apoE4), the most prevalent genetic risk factor for AD, also increases the risk for dementia in pure synucleinopathies. We presently examined the effects of α‐synuclein deficiency (α‐syn−/−) and sex on apoE4‐driven pathologies. Methods AD‐related, synaptic, and vascular markers were analyzed in female and male α‐syn−/− and α‐syn+/+ apoE4, apoE3, and apoE3/E4 mice. Results ApoE4 was hypolipidated, and this effect was unchanged by α‐syn−/− and sex. The levels of synaptic markers were lower, and the levels of AD‐related parameters were higher in female α‐syn−/− apoE4 mice compared with the corresponding apoE3 mice. By comparison, apoE4 had small effects on the AD parameters of male and female α‐syn+/+ apoE4 mice. Discussion Although α‐syn−/− does not affect the upstream lipidation impairment of apoE4, it acts as a “second hit” enhancer of the subsequent apoE4‐driven pathologies.