Stephania Libreros

Occupational exposure to engineered nanomaterials (ENMs) is increasing in the workplace and can impact human health. Amorphous silicon dioxide nanoparticles (SiO₂ NPs) are widely produced respirable ENMs used in commercial products. We have investigated their impact on lung inflammation resolution and bacterial defense. Mice exposed to SiO₂ NPs, followed by bacteria, exhibited increased lung inflammation, bacterial proliferation, and lung damage compared to mice not exposed to NPs. SiO₂ NPs increased human macrophage production of pro-inflammatory mediators and disrupted phagocytosis of bacteria and efferocytosis of apoptotic neutrophils – pivotal responses for host defense and inflammation resolution. A pro-resolving mediator, resolvin D5 (RvD5), restored macrophage phagocytosis of bacteria and partially controlled excess lung inflammation after SiO₂ NPs. These findings demonstrate that SiO₂ NPs disrupt endogenous resolution processes to give rise to heightened lung inflammation and infection. RvD5 reduced inflammation and partially restored endogenous resolution cellular processes, suggesting that RvD5 can reduce ENP disruption of resolution.

Acute inflammation is the body’s first defense in response to pathogens or injury that is partially governed by a novel genus of endogenous lipid mediators that orchestrate the resolution of inflammation, coined specialized pro-resolving mediators (SPMs). SPMs, derived from omega-3-polyunstaturated fatty acids (PUFAs), include the eicosapentaenoic acid-derived and docosahexaenoic acid-derived Resolvins, Protectins, and Maresins. Herein, we review their biosynthesis, structural characteristics, and therapeutic effectiveness in various diseases such as ischemia, viral infections, periodontitis, neuroinflammatory diseases, cystic fibrosis, lung inflammation, herpes virus, and cancer, especially focusing on therapeutic effectiveness in respiratory inflammation and ischemia-related injuries. Resolvins are sub-nanomolar potent agonists that accelerate the resolution of inflammation by reducing excessive neutrophil infiltration, stimulating macrophage functions including phagocytosis, efferocytosis, and tissue repair. In addition to regulating neutrophils and macrophages, Resolvins control dendritic cell migration and T cell responses, and they also reduce the pro-inflammatory cytokines, proliferation, and metastasis of cancer cells. Importantly, several lines of evidence have demonstrated that Resolvins reduce tumor progression in melanoma, oral squamous cell carcinoma, lung cancer, and liver cancer. In addition, Resolvins enhance tumor cell debris clearance by macrophages in the tumor’s microenvironment. Resolvins, with their unique stereochemical structure, receptors, and biosynthetic pathways, provide a novel therapeutical approach to activating resolution mechanisms during cancer progression.

For either healthy or diseased organisms, lipids are key components for cellular membranes; they play important roles in numerous cellular processes including cell growth, proliferation, differentiation, energy storage and signaling. Exercise and disease development are examples of cellular environment alterations which produce changes in these networks. There are indications that alterations in lipid metabolism contribute to the development and progression of a variety of cancers. Measuring such alterations and understanding the pathways involved is critical to fully understand cellular metabolism. The demands for this information have led to the emergence of lipidomics, which enables the large-scale study of lipids using mass spectrometry (MS) techniques. Mass spectrometry has been widely used in lipidomics and allows us to analyze detailed lipid profiles of cancers. In this article, we discuss emerging strategies for lipidomics by mass spectrometry; targeted, as opposed to global, lipid analysis provides an exciting new alternative method. Additionally, we provide an introduction to lipidomics, lipid categories and their major biological functions, along with lipidomics studies by mass spectrometry in cancer samples. Further, we summarize the importance of lipid metabolism in oncology and tumor microenvironment, some of the challenges for lipodomics, and the potential for targeted approaches for screening pharmaceutical candidates to improve the therapeutic efficacy of treatment in cancer patients.

Purpose of review: Acute inflammation is the body's first defense in response to pathogens or injury. Failure to efficiently resolve the inflammatory insult can severely affect tissue homeostasis, leading to chronic inflammation. Neutrophils play a pivotal role in eradicating infectious pathogens, orchestrating the initiation and resolution of acute inflammation, and maintaining physiological functions. The resolution of inflammation is a highly orchestrated biochemical process, partially modulated by a novel class of endogenous lipid mediators known as specialized pro-resolving mediators (SPMs). SPMs mediate their potent bioactions via activating specific cell-surface G protein-coupled receptors (GPCR). Recent findings: This review focuses on recent advances in understanding the multifaceted functions of SPMs, detailing their roles in expediting neutrophil apoptosis, promoting clearance by macrophages, regulating their excessive infiltration at inflammation sites, orchestrating bone marrow deployment, also enhances neutrophil phagocytosis and tissue repair mechanisms under both physiological and pathological conditions. We also focus on the novel role of SPMs in regulating bone marrow neutrophil functions, differentiation, and highlight open questions about SPMs’ functions in neutrophil heterogeneity. Summary: SPMs play a pivotal role in mitigating excessive neutrophil infiltration and hyperactivity within pathological milieus, notably in conditions such as sepsis, cardiovascular disease, ischemic events, and cancer. This significant function highlights SPMs as promising therapeutic agents in the management of both acute and chronic inflammatory disorders.

The elusive nature of the liver immune system in newborns remains an important challenge, casting a shadow over our understanding of how to effectively treat and prevent diseases in children. Therefore, deeper exploration into the intricacies of neonatal immunology might be crucial for improved pediatric healthcare. Using liver intravital microscopy, we unveiled a significant population of granulocytes in the hepatic parenchyma of fetuses and newborns. Utilizing high-dimensional immunophenotyping, we showed dynamic alterations predominantly in granulocytes during neonatal development. Liver intravital microscopy from birth through adulthood captures real-time dynamics, showing a substantial presence of Ly6G+ cells that persisted significantly up to 2 wk of age. Using time-of flight mass cytometry, we characterized neonatal Ly6G+ cells as neutrophils, confirmed by morphology and immunohistochemistry. Surprisingly, the embryonic liver hosts a distinct population of neutrophils established as early as the second gestational week, challenging conventional notions about their origin. Additionally, we observed that embryonic neutrophils occupy preferentially the extravascular space, indicating their early establishment within the liver. Hepatic neutrophils in embryos and neonates form unique cell clusters, persisting during the initial days of life, while reduced migratory capabilities in neonates are observed, potentially compensating with increased reactive oxygen species release in response to stimuli. Finally, in vivo imaging of acute neutrophil behavior in a newborn mouse, subjected to focal liver necrosis, unveils that neonatal neutrophils exhibit a reduced migratory response. The study provides unprecedented insights into the intricate interplay of neutrophils within the liver, shedding light on their functional and dynamic characteristics during development.

Neutrophils reside in the bone marrow (BM), ready for deployment to sites of injury/infection, initiating inflammation and its resolution. Here, we report that distal infections signal to the BM via resolvins to regulate granulopoiesis and BM neutrophil deployment. Emergency granulopoiesis during peritonitis evoked changes in BM resolvin D1 (RvD1) and BM RvD4. We found that leukotriene B4 stimulates neutrophil deployment. RvD1 and RvD4 each limited neutrophilic infiltration to infections, and differently regulated BM myeloid populations: RvD1 increased reparative monocytes, and RvD4 regulated granulocytes. RvD4 disengaged emergency granulopoiesis, prevented excess BM neutrophil deployment, and acted on granulocyte progenitors. RvD4 also stimulated exudate neutrophil, monocyte, and macrophage phagocytosis, and enhanced bacterial clearance. This mediator accelerated both neutrophil apoptosis and clearance by macrophages, thus expediting the resolution phase of inflammation. RvD4 stimulated phosphorylation of ERK1/2 and STAT3 in human BM-aspirate–derived granulocytes. RvD4 in the 1 to 100 nM range stimulated whole-blood neutrophil phagocytosis of Escherichia coli. RvD4 increased BM macrophage efferocytosis of neutrophils. Together, these results demonstrate the novel functions of resolvins in granulopoiesis and neutrophil deployment, contributing to the resolution of infectious inflammation.

Specialized pro‐resolving lipid mediators play key functions in the resolution of the acute inflammatory response. Herein, we elucidate the stereochemical structure of the new 4S,5R‐RCTR1, a cysteinyl‐resolvin, recently uncovered in human leukocytes incubated with a 4S,5S‐epoxy‐resolvin intermediate, using liquid chromatography–tandem mass spectrometry (LC–MS/MS) and ultra‐violet (UV) spectrophotometry. With this approach, the physical properties of the new mediator prepared by total organic synthesis were matched to enzymatically produced biogenic material. In addition, we confirmed the potent biological actions of 4S,5R‐RCTR1 with human M2‐like macrophage phagocytosis of live bacteria, efferocytosis of apoptotic neutrophils, and erythrophagocytosis of senescent human red blood cells in a concentration‐dependent manner from 0.1 to 10 nM. Taken together, these results establish the complete stereochemistry of 4S,5R‐RCTR1 as 5R‐glutathionyl‐4S,17S‐dihydroxy‐6E,8E,10Z,13Z,15E,19Z‐docosahexaenoic acid and give evidence of its novel bioactivities in human phagocyte responses. Moreover, they confirm and extend the stereoselective functions of the 4S,5R‐RCTR1 with isolated human phagocytes of interest in the resolution of inflammation.

The recently elucidated proresolving conjugates in tissue regeneration (CTR) maresin-CTR (MCTR), protectin-CTR (PCTR), and resolvin-CTR (RCTR), termed cysteinyl-specialized proresolving mediators (cys-SPMs) each promotes regeneration, controls infection, and accelerates resolution of inflammation. Here, we sought evidence for cys-SPM activation of primordial pathways in planaria (Dugesia japonica) regeneration that might link resolution of inflammation and regeneration. On surgical resection, planaria regeneration was enhanced with MCTR3, PCTR3, or RCTR3 (10 nM), each used for RNA sequencing. The three cys-SPMs shared up-regulation of 175 known transcripts with fold-change > 1.25 and combined false discovery rate (FDR) < 0.002, and 199 canonical pathways (FDR < 0.25), including NF-κB pathways and an ortholog of human TRAF3 (TNFR-associated factor 3). Three separate pathway analyses converged on TRAF3 up-regulation by cys-SPMs. With human macrophages, three cys-SPMs each dose-dependently increased TRAF3 expression in a cAMP-PKA–dependent manner. TRAF3 overexpression in macrophages enhanced Interleukin-10 (IL-10) and phagocytosis of Escherichia coli. IL-10 also increased phagocytosis in a dose-dependent manner. Silencing of mouse TRAF3 in vivo significantly reduced IL-10 and macrophage phagocytosis. TRAF3 silencing in vivo also relieved cys-SPMs’ actions in limiting polymorphonuclear neutrophil in E. coli exudates. These results identify cys-SPM–regulated pathways in planaria regeneration, uncovering a role for TRAF3/IL-10 in regulating mammalian phagocyte functions in resolution. Cys-SPM activation of TRAF3 signaling is a molecular component of both regeneration and resolution of infectious inflammation. Significance Resolution of inflammation, infection, and injury are essential for host defense and homeostasis. Cysteinyl-specialized proresolving mediators (cys-SPMs) are potent chemical signals that accelerate resolution of inflammation, control infection, and display proregenerative properties. We sought evidence for cys-SPM–activated primordial pathways that might link resolution of inflammation and regeneration using planaria because of their robust regenerative ability. RNA sequencing was carried out with surgically resected planaria exposed to cys-SPMs, and we identified genes and pathways regulated by cys-SPMs during the regeneration, including TRAF3. In mammalian systems, TRAF3 contributes to cys-SPM–stimulated phagocyte functions and resolution of infection.

Resolution of acute inflammation is an active process orchestrated by endogenous mediators and mechanisms pivotal in host defense and homeostasis. The macrophage mediator in resolving inflammation, maresin 1 (MaR1), is a potent immunoresolvent, stimulating resolution of acute inflammation and organ protection. Using an unbiased screening of greater than 200 GPCRs, we identified MaR1 as a stereoselective activator for human leucine-rich repeat containing G protein–coupled receptor 6 (LGR6), expressed in phagocytes. MaR1 specificity for recombinant human LGR6 activation was established using reporter cells expressing LGR6 and functional impedance sensing. MaR1-specific binding to LGR6 was confirmed using ³H-labeled MaR1. With human and mouse phagocytes, MaR1 (0.01–10 nM) enhanced phagocytosis, efferocytosis, and phosphorylation of a panel of proteins including the ERK and cAMP response element-binding protein. These MaR1 actions were significantly amplified with LGR6 overexpression and diminished by gene silencing in phagocytes. Thus, we provide evidence for MaR1 as an endogenous activator of human LGR6 and a novel role of LGR6 in stimulating MaR1’s key proresolving functions of phagocytes.