Biology subjects

Almeida, M. R.

Publications and source records attributed to Almeida, M. R..

3 recordsLinked to original sources

bioRxiv2025

Transthyretin Levels and Instability in Alzheimer's Disease: Correlations with AD Biomarkers in a Cohort Study

BackgroundIn the last few decades, Transthyretin (TTR) has gained attention due to its implication in brain functions and neurodegenerative conditions, such as Alzheimers Disease (AD) by modulating amyloid-beta (A{beta}) pathology. This study aims to assess TTR levels and tetrameric instability in both plasma and cerebrospinal fluid (CSF) across the clinical continuum of AD, and to establish associations between TTR and key AD biomarkers, to enhance our understanding of the role of TTR in AD pathogenesis. MethodsWe conducted an evaluation of TTR levels and tetrameric instability in plasma and CSF in mild cognitive impairment (MCI-AD, n=29) and Dementia-AD (n=37) patients and examined the association with clinical, biochemical and genetic data. ResultsKey findings revealed a substantial decrease in plasma TTR levels in the Dementia-AD patients compared to the MCI-AD group, with a pronounced gender-specific effect identified in women, while no differences were detected in the CSF. The search for associations identified several correlations amongst MCI-AD patients where CSF TTR levels inversely correlated with markers of amyloid pathology and neurodegeneration such as A{beta}40 (r=-0.43, p < 0.02), p-Tau181 (r=-0.54, p < 0.03), t-Tau (r=-0.57, p< 0.001) and NfL (r=-0.49, p<0.006). CSF TTR instability also correlated negatively with CSF A{beta}42 (r=-0.6, p<0.001) and A{beta}42/A{beta}40 ratio (r=-0.58, p<0.001), indicating an association with increased amyloid burden. In the Dementia-AD group, plasma TTR levels correlated negatively with GFAP (r=-0.4, p<0.014), reflecting potential links with neuroinflammation. Additionally, plasma TTR instability correlated with CSF TTR instability (r=0.42, p < 0.009) and tau pathology markers (p-Tau181 (r=0.38, p < 0.02) and t-Tau (r=0.42, p<0.09)). Given the strong association between CSF TTR instability and A{beta}42, we investigated the effect of the peptide on TTR tetrameric instability and showed a clear increase in TTR instability in samples incubated with A{beta}42 for 24 hours (p<0.05). ConclusionsThis study emphasizes several associations between TTR and other key indicators of AD and suggests TTR is associated with A{beta} clearance, neurodegeneration, and neuroinflammation across different stages of the disease. We propose A{beta}42 and its increase in the brain as a factor destabilizing the TTR tetrameric fold, resulting in TTR impaired function.

neuroscience↗

bioRxiv2024

Proteomic And Transcriptomic Host Biomarkers For Detection Of Pleural Tuberculosis

Current diagnosis of pleural tuberculosis (PLTB) is based on highly invasive procedures. Therefore, blood-based host biomarkers could represent a low-invasive diagnostic alternative. Plasma and pleural effusion, as well as blood-and pleural fluid mononuclear cells (PBMCs and PFMCs), were sampled from patients with PLTB and other pleural diseases (OPLDs). In pleural effusion, ApoA1, C1q, CRP, IL-6, IFN-{gamma}, IP-10, MIG, S100A12, SAA1/A2, and serpin-A3 were significantly higher in PLTB compared to OPLD, whereas only SAA1/A2 showed discriminatory potential in plasma. Increased mRNA levels were observed in PFMCs of PLTB for CD8A, GBP5, SLAMF7, CXCL10, IL2, GNLY, IL23A, PDCD1 and BCMA, whereas HMOX1, CD163, DUSP3, IGF1, GUSB and MARCO were decreased. In PBMCs of PLTB, only CCL22 expression was decreased. GBP5 was significantly higher expressed in PLTB for both cell types. This study shows the potential of transcriptomic and proteomic host biomarkers to differentiate PLTB from OPLDs also when applying low-invasive methods.

microbiology↗

bioRxiv2023

In Campylobacter jejuni a new type of chaperone receives heme b from ferrochelatase

Intracellular heme formation and trafficking are fundamental processes in living organisms. Three biogenesis pathways are used by bacteria and archaea to produce iron protoporphyrin IX (heme b) that diverge after the formation of the common intermediate uroporphyrinogen III (urogen III). In this work, we identify and provide a detailed characterization of the enzymes involved in the transformation of urogen III into heme. We show that in this organism operates the protoporphyrin-dependent pathway (PPD pathway), in which the last reaction is the incorporation of ferrous iron into the porphyrin ring by the ferrochelatase enzyme. In general, following this final reaction, little is known about how the formed heme b reaches the target proteins. In particular, the chaperons that are thought to be required to traffic heme for incorporation into hemeproteins to avoid the cytotoxicity associated to free heme, remain largely unidentified. We identified in C. jejuni a chaperon-like protein, named CgdH2, that binds heme with a dissociation constant of 4.9 {+/-} 1.0 {micro}M, a binding that is impaired upon mutation of residues histidine 45 and 133. We show that C. jejuni CgdH2 establishes protein-protein interactions with ferrochelatase, which should enable for the observed transfer of heme from ferrochelatase to CgdH2. Phylogenetic analysis revealed that C. jejuni CgdH2 is evolutionarily distinct from the currently known chaperones. Therefore, CgdH2 is a novel chaperone and the first protein identified as an acceptor of the intracellularly formed heme, thus enlarging our understanding of bacterial heme homeostasis.

biochemistry↗