Juliet Akkaoui

https://nsuworks.nova.edu/cnso_alumni/1176/thumbnail.jp

LRRC25 expression during physiological aging and in mouse models of Alzheimer’s disease and iPSC-derived neurons

The leucine-rich repeat-containing protein 25 (LRRC25) is relatively a novel protein with no information on its role in neuronal or brain function. A recent study suggested LRRC25 is a potential risk factor for Alzheimer’s disease (AD). As a first step to understanding LRRC25’s role in the brain and AD, we found LRRC25 is expressed in both cell membranes and cytoplasm in a punctuate appearance in astrocytes, microglia, and neurons in cell lines as well as mouse brain. We also found that LRRC25 expression is both age- and brain region-dependent and that 1-day-old (1D) pups expressed the least amount of LRRC25 protein compared to adult ages. In the APΔE9 mice, immunoblot quantified LRRC25 protein levels were increased by 166% (**p < 0.01) in the cortex (CX) and by 215% (***p < 0.001) in the hippocampus (HP) relative to wild-type (WT) controls. Both the brainstem (BS) and cerebellum (CB) showed no significant alterations. In the 3xTg mice, only CX showed an increase of LRRC25 protein by 91% (*p < 0.05) when compared to WT controls although the increased trend was noted in the other brain regions. In the AD patient brains also LRRC25 protein levels were increased by 153% (***p < 0.001) when compared to normal control (NC) subjects. Finally, LRRC25 expression in the iPSC-derived neurons quantified by immunofluorescence was increased by 181% (**p < 0.01) in AD-derived neurons when compared to NC-derived neurons. Thus increased LRRC25 protein in multiple models of AD suggests that LRRC25 may play a pathogenic role in either Aβ or tau pathology in AD. The mechanism for the increased levels of LRRC25 in AD is unknown at present, but a previous study showed that LRRC25 levels also increase during neonatal hypoxic-ischemia neuronal damage. Based on the evidence that autophagy is highly dysregulated in AD, the increased LRRC25 levels may be due to decreased autophagic degradation of LRRC25. Increased LRRC25 in turn may regulate the stability or activity of key enzymes involved in either Aβ or hyperphosphorylated tau generation and thus may contribute to increased plaques and neurofibrillary tangles

Role of Cathepsin-B in the Osteoclastogenic Effect of Porphyromonas Gingivalis- Phosphoglycerol Dihydroceramide

Objective: This study aims to evaluate the impact of the PGDHC/CtsB axis on RANKL-mediated osteoclastogenesis. Background: Cathepsin-B (CtsB) is a lysosomal-cysteine-protease associated with pathological processes. CtsB regulates RANKL-mediated osteoclastogenesis through degradation of non-muscle myosin IIA (Myh9). We recently demonstrated that phosphoglycerol dihydroceramide (PGDHC) from Porphyromonas gingivalis upregulated osteoclastogenesis in a Myh9-dependent manner. However, activation of CtsB by PGDHC in periodontal bone loss is unclear. Methods: RANKL-stimulated RAW264.7 cells were exposed to PGDHC in the presence/absence of membrane impermeable CtsB inhibitor CA-074, and membrane permeable CtsB inhibitor CA-074 Me. TRAP staining was performed at day 4 to identify mature osteoclasts and pit formation assay was performed at day 7 to assess osteoclast activity. Intracellular CtsB activity and extracellular inflammatory cytokine expression were assessed after 48 and 96 hours. Results: PGDHC upregulated RANKL-induced osteoclastogenesis of RAW 264.7 cells. CA-074-Me, but not CA-074, inhibited osteoclastogenesis and mature osteoclast activity. PGDHC increased CtsB activity after 48h and induced extracellular expression of Tnf-α and IL-1β after 96h. However, only the overexpression of IL-1β was CtsB mediated. Conclusion: PGDHC promotes osteoclastogenesis via upregulation of intracellular CtsB activity in pre-osteoclasts. PGDHC does not induce an inflammatory effect on pre-osteoclasts but increases the production of inflammatory cytokines by mature osteoclasts through CtsB dependent and independent pathways. These results may lead to a better understanding of bacterial osteolysis, as in periodontitis, and development of novel anti-bone loss therapy. Grants: This study was funded by the NIH grant R03-7-16-2018 and NIDCR administrative research supplement to promote diversity in health-related researc

Elusive Roles of the Different Ceramidases in Human Health, Pathophysiology, and Tissue Regeneration

Ceramide and sphingosine are important interconvertible sphingolipid metabolites which govern various signaling pathways related to different aspects of cell survival and senescence. The conversion of ceramide into sphingosine is mediated by ceramidases. Altogether, five human ceramidases—named acid ceramidase, neutral ceramidase, alkaline ceramidase 1, alkaline ceramidase 2, and alkaline ceramidase 3—have been identified as having maximal activities in acidic, neutral, and alkaline environments, respectively. All five ceramidases have received increased attention for their implications in various diseases, including cancer, Alzheimer’s disease, and Farber disease. Furthermore, the potential anti-inflammatory and anti-apoptotic effects of ceramidases in host cells exposed to pathogenic bacteria and viruses have also been demonstrated. While ceramidases have been a subject of study in recent decades, our knowledge of their pathophysiology remains limited. Thus, this review provides a critical evaluation and interpretive analysis of existing literature on the role of acid, neutral, and alkaline ceramidases in relation to human health and various diseases, including cancer, neurodegenerative diseases, and infectious diseases. In addition, the essential impact of ceramidases on tissue regeneration, as well as their usefulness in enzyme replacement therapy, is also discussed

IL-34 exacerbates pathogenic features of Alzheimer\u27s disease and calvaria osteolysis in triple transgenic (3x-Tg) female mice.

Hallmark features of Alzheimer\u27s disease (AD) include elevated accumulation of aggregated Aβ40 and Aβ42 peptides, hyperphosphorylated Tau (p-Tau), and neuroinflammation. Emerging evidence indicated that interleukin-34 (IL-34) contributes to AD and inflammatory osteolysis via the colony-stimulating factor-1 receptor (CSF-1r). In addition, CSF-1r is also activated by macrophage colony-stimulating factor-1 (M-CSF). While the role of M-CSF in bone physiology and pathology is well addressed, it remains controversial whether IL-34-mediated signaling promotes osteolysis, neurodegeneration, and neuroinflammation in relation to AD. In this study, we injected 3x-Tg mice with mouse recombinant IL-34 protein over the calvaria bone every other day for 42 days. Then, behavioral changes, brain pathology, and calvaria osteolysis were evaluated using various behavioral maze and histological assays. We demonstrated that IL-34 administration dramatically elevated AD-like anxiety and memory loss, pathogenic amyloidogenesis, p-Tau, and RAGE expression in female 3x-Tg mice. Furthermore, IL-34 delivery promoted calvaria inflammatory osteolysis compared to the control group. In addition, we also compared the effects of IL-34 and M-CSF on macrophages, microglia, and RANKL-mediated osteoclastogenesis in relation to AD pathology in vitro. We observed that IL-34-exposed SIM-A9 microglia and 3x-Tg bone marrow-derived macrophages released significantly elevated amounts of pro-inflammatory cytokines, TNF-α, IL-1β, and IL-6, compared to M-CSF treatment in vitro. Furthermore, IL-34, but not M-CSF, elevated RANKL-primed osteoclastogenesis in the presence of Aβ40 and Aβ42 peptides in bone marrow derived macrophages isolated from female 3x-Tg mice. Collectively, our data indicated that IL-34 elevates AD-like features, including behavioral changes and neuroinflammation, as well as osteoclastogenesis in female 3x-Tg mice