Biology subjects

Santos, R. S.

Publications and source records attributed to Santos, R. S..

5 recordsLinked to original sources

bioRxiv2026

Psychoneuroimmunology of Viral Hepatitis and Hepatocellular Carcinoma: A Systematic Review and Meta-Analysis

Hepatocellular carcinoma (HCC) and viral hepatitis (VH) are recognized primarily as hepatic diseases, yet they impose a substantial neuropsychiatric disorders (NPDs) encompassing depression, anxiety, cognitive impairment, and fatigue. Whether these manifestations reflect psychological reactions or biologically grounded psychoneuroimmune dysfunction remains poorly understood. Here, we present a pre-registered systematic review and meta-analysis (PROSPERO 2026 CRD420251081757) synthesizing evidence from 24 studies combining psychosocial outcomes with immune dysregulation markers across HCC and VH populations. Bibliometric and network analyses identified a growing psychoneuroimmunology research hub linking cytokine signaling, microglial activation, blood-brain barrier (BBB) disruption, and gut-liver-brain axis dysregulation to the neuropsychiatric phenotype of these diseases. Meta-analysis revealed a pooled hazard ratio (HR) of 1.92 (95% CI: 1.09-3.39) for adverse outcomes in HCC and a pooled HR of 2.28 (95% CI: 1.48-3.52) for depression associated to genetic variants in VH. TNF-a, but not IL-6, showed a tendency toward lower levels in VH patients with versus without NPDs, suggesting differential inflammatory roles. The literature, however, remains fragmented by heterogeneous designs and a paucity of longitudinal data. A psychoneuroimmunological approach, integrating immune, endocrine, neural, and psychosocial dimensions, is essential for capturing the full systemic impact of HCC and VH and should inform future mechanistic research and multidisciplinary clinical strategies.

cancer biology↗

bioRxiv2024

Comparative study of Ergosterol and 7-dehydrocholesterol and their Endoperoxides: Generation, Identification and Impact in Phospholipid Membranes and Melanoma Cells

Melanoma is an aggressive cancer that has attracted attention in recent years due to its high mortality rate of 80%. Damage caused by oxidative stress generated by radical (type I reaction) and singlet oxygen, 1O2 (type II reaction) oxidative reactions may induce cancer. Thus, studies that aim to unveil the mechanism that drives these oxidative damage processes become relevant. Ergosterol, an analogue of 7-dehydrocholesterol, important in the structure of cell membranes, is widely explored in cancer treatment. However, to date little is known about the impact of different oxidative reactions on these sterols in melanoma treatment, and conflicting results about their effectiveness complicates the understanding of their role in oxidative damage. Our results highlight differences among ergosterol, 7-dehydrocholesterol (7-DHC) and cholesterol in membrane properties when subjected to distinct oxidative reactions. Furthermore, we conducted a comparative study exploring the mechanisms of cell damage by photodynamic treatment in A375 melanoma. Notably, endoperoxides from ergosterol and 7-DHC generated by 1O2 showed superior efficacy in reducing the viability of A375 cells compared to their precursor molecules. We also describe a step-by-step process to produce and identify endoperoxides derived from ergosterol and 7-DHC. While further studies are needed, this work provides new insights for understanding cancer cell death induced by different oxidative reactions in the presence of biologically relevant sterols.

biochemistry↗

bioRxiv2024

Genome-directed study uncovers a family of phospholipases and highlights the diversity of Salmonella T6SS effectors.

Bacterial warfare is a common and ancient phenomenon in nature, where bacterial species use strategies to inhibit the growth or kill competitors. This involves the production and deployment of antibacterial toxins that disrupt essential cellular processes in target cells. The continuous arms race in which bacteria acquire new toxin and immunity proteins to promote increased adaptation to their environment is responsible for the diversification of this toxin repertoire. Here, we deployed in-silico strategies to analyze 10,000 genomes and identify effectors secreted via the type VI secretion system of Salmonella. We identified 128 candidates, which are widespread in a vast array of Salmonella serovars and other bacterial species. Tox-Act1 is among the most frequent candidates and was selected for in-depth characterization. Tox-Act1 contains a permuted NlpC/P60 papain-like catalytic core characteristic of lipid-targeting members rather than the typical peptidases or amidases. Evolutionary analysis revealed the relationship of Tox-Act1 with acyltransferases. Biochemical assays with purified toxin and lipidomics of intoxicated cells showed that Tox-Act1 exhibits phospholipase activity, cleaving off acyl groups from phosphatidylglycerol and phosphatidylethanolamine. In addition, we demonstrate that Tox-Act1 is secreted in a T6SS-dependent manner and provide a competitive advantage during colonization of the gut of infected mice. This work broadens our understanding of toxin domains and provides the first direct characterization of a lipid-targeting NlpC/P60 domain in biological conflicts.

microbiology↗

bioRxiv2023

Plasma Oxylipin Profiling by High Resolution Mass Spectrometry Reveal Signatures of Inflammation and Hypermetabolism in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized not only by progressive loss of motor neurons, but also linked to systemic hypermetabolism, oxidative stress, and inflammation. In this context, oxylipins have been investigated as signaling molecules linked to neurodegeneration. However, the nature and role of major oxylipins involved in ALS disease progression remain unclear. Importantly, most methods focused on oxylipin analysis are based on low resolution mass spectrometry (LRMS), which usually confers high sensitivity, but not great accuracy for lipid identification, as provided by high-resolution MS (HRMS). Here, we established an ultra-high performance liquid chromatography coupled HRMS (LC-HRMS) method for simultaneous analysis of 126 oxylipins in plasma, including lipid hydroxides, ketones, epoxides, prostaglandins, leukotrienes, and others in a 15-minute run. Intra- and inter-day method validation showed high sensitivity (0.3 - 25 pg), accuracy and precision for more than 90 % of quality controls. This method was applied for the analysis of oxylipins in plasma of ALS rats overexpressing the mutant human Cu/Zn-superoxide dismutase gene (SOD1-G93A) at asymptomatic (ALS 70 days old) and symptomatic stages (ALS 120 days old), and their respective age-matched wild type controls (WT 70 days old and WT 120 days old). From the 56 oxylipins identified in plasma, 17 species were significantly altered. Remarkably, most of oxylipins linked to inflammation and oxidative stress derived from arachidonic acid, such as, prostaglandins, lipoxins, mono-hydroxides, and isoprostane, were increased in ALS 120d rats. In contrast, the linoleic acid diols involved in fatty acid uptake and {beta}-oxidation, 9(10)-DiHOME and 12(13)-DiHOME, were strongly decreased in the ALS 120d. In summary, we developed and validated a high-throughput LC-HRMS method for oxylipin analysis and provided a comprehensive overview of plasma oxylipins involved in ALS disease progression. Noteworthy, the oxylipins altered in plasma of ALS 120d rats have potential to be investigated and used as biomarkers for inflammation and hypermetabolism in ALS. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=136 SRC="FIGDIR/small/547101v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@937099org.highwire.dtl.DTLVardef@1c5847forg.highwire.dtl.DTLVardef@7dd09borg.highwire.dtl.DTLVardef@a9f8d_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2018

Inhibition Of Nitric Oxide Synthesis By Dexamethasone Increases Survival Rate In Plasmodium berghei-Infected Mice

Malaria still presents great epidemiologic importance by its high incidence in the world and potential clinical severity. Plasmodium parasites are highly susceptible to changes in the redox balance and the relationship between the redox state of the parasite and host cells is very complex and involves nitric oxide (NO) synthesis. Thus, the present study is aimed at evaluating the effects of NO synthesis on the redox status, parasitemia evolution and survival rate of Plasmodium berghei-infected mice. Two-hundred and twenty-five mice were infected with Plasmodium berghei and submitted to the stimulation or inhibition of NO synthesis. The stimulation of NO synthesis was performed through the administration of L-arginine, while its inhibition was made by the administration of dexamethasone. Inducible NO synthase (iNOS) inhibition by dexamethasone promoted an increase in the survival rate of P. berghei-infected mice and data suggested the participation of oxidative stress in brain as a result of plasmodial infection, as well as the inhibition of brain NO synthesis, which promoted survival rate of almost 90% of the animals until the 15th day of infection, with possible direct interference of ischemia and reperfusion syndrome, as seen by increased levels of uric acid. Inhibition of iNOS caused a decrease of parasitemia and increased survival rate of infected animals, suggesting that the synthesis of NO may stimulate a series of compensatory redox effects that, if overstimulated, may be responsible for the onset of severe forms of malaria.

microbiology↗