Changes in macrophage function modulated by the lipid environment

Cholesterol dysregulation in peripheral blood mononuclear cells of Alzheimer's disease

Cholesterol and the immune system are involved in Alzheimer's Disease (AD). To investigate the relations among them, we compared the cholesterol content in peripheral blood mononuclear cells (PBMC) of cognitively healthy controls and patients with mild cognitive impairment (MCI) and AD in two independent samples. Free cholesterol content of PBMC was lower in MCI and AD patients, and was modulated by APOE genotype. A decrease of CD8+ and an increase of CD16+ was also found in AD patients. These results suggest that cholesterol levels in PBMCs may represent an early signature of the disease and support the involvement of immune system in AD.

Ayurvedic lipid based rasayans - A perspective on the preparation and pharmacological significance of lipids on the bioavailability of phytoconstituents

For thousands of years, lipid based Ayurvedic formulations have been made in India, and the craft has survived down the millennia up to the present time. Some of these deliciously potent phytonutrient preparations are very popular and have sustained the test of time pertaining to their efficacy. Recent researches on the role of phytonutrients in promoting cardio-pulmonary, brain and immune health substantially buttress the philosophy underlying the use of lipids in preparing these emulsions, since a large number of these bioactives are lipophilic. Being lipoidic, they are absorbed through the lacteals in the small intestine, and are then transported through the thoracic duct directly to the heart, bypassing the liver. The formulations utilizing ghee (clarified butter) or sesame oil as the carrier lipid, either while frying the myrobalams or as Anupana (adjuvant), have special significance in modulating bodily immunity, since the immune system is housed in lymphatics which are lipid rich. Amla and lipid based Ayurvedic rasayans (rejuvenating formulations) are a popular and highly palatable group of phytonutraceutical preparations. This group of polyherbal adaptogenic formulations is classified separately from other formulations in Ayurvedic therapeutics. Several of these health-promoting rasayans are suitable to be consumed by all age-groups in the recommended season and dose. Current research on endothelial and immune cell receptor mediated uptake of lipoidic molecules, together with the knowledge of lipid absorption pathways, lends credence to the usefulness of rasayans in targeting the cardio-pulmonary and immune systems. An attempt has been made in this paper to elucidate the mechanisms underpinning the complex interplay between lipid delivered hydrophobic phyto-molecules, systemic lymphatics and the Immune system.

Statins and Bempedoic Acid: Different Actions of Cholesterol Inhibitors on Macrophage Activation

Statins represent the most prescribed class of drugs for the treatment of hypercholesterolemia. Effects that go beyond lipid-lowering actions have been suggested to contribute to their beneficial pharmacological properties. Whether and how statins act on macrophages has been a matter of debate. In the present study, we aimed at characterizing the impact of statins on macrophage polarization and comparing these to the effects of bempedoic acid, a recently registered drug for the treatment of hypercholesterolemia, which has been suggested to have a similar beneficial profile but fewer side effects. Treatment of primary murine macrophages with two different statins, i.e., simvastatin and cerivastatin, impaired phagocytotic activity and, concurrently, enhanced pro-inflammatory responses upon short-term lipopolysaccharide challenge, as characterized by an induction of tumor necrosis factor (TNF), interleukin (IL) 1β, and IL6. In contrast, no differences were observed under long-term inflammatory (M1) or anti-inflammatory (M2) conditions, and neither inducible NO synthase (iNOS) expression nor nitric oxide production was altered. Statin treatment led to extracellular-signal regulated kinase (ERK) activation, and the pro-inflammatory statin effects were abolished by ERK inhibition. Bempedoic acid only had a negligible impact on macrophage responses when compared with statins. Taken together, our data point toward an immunomodulatory effect of statins on macrophage polarization, which is absent upon bempedoic acid treatment.

A data-driven computational model enables integrative and mechanistic characterization of dynamic macrophage polarization

Macrophages are highly plastic immune cells that dynamically integrate microenvironmental signals to shape their own functional phenotypes, a process known as polarization. Here we develop a large-scale mechanistic computational model that for the first time enables a systems-level characterization, from quantitative, temporal, dose-dependent, and single-cell perspectives, of macrophage polarization driven by a complex multi-pathway signaling network. The model was extensively calibrated and validated against literature and focused on in-house experimental data. Using the model, we generated dynamic phenotype maps in response to numerous combinations of polarizing signals; we also probed into an in silico population of model-based macrophages to examine the impact of polarization continuum at the single-cell level. Additionally, we analyzed the model under an in vitro condition of peripheral arterial disease to evaluate strategies that can potentially induce therapeutic macrophage repolarization. Our model is a key step toward the future development of a network-centric, comprehensive "virtual macrophage" simulation platform.

Bacterial Lectin-Targeting Glycoconjugates for Selective Elimination of Pathogenic Bacteria

Herein we report a strategy to eradicate pathogenic bacteria selectively, which utilizes bacterial lectin-targeting glycoconjugates that contain an epitope or a photosensitizer to promote antibody-dependent cellular cytotoxicity (ADCC) or photodynamic therapy (PDT), respectively. Our results show that death promoted by using the designed synthetic glycoconjugates coupled with ADCC or PDT takes place selectively in pathogenic bacteria expressing lectins on their surfaces.

Peroxisomes in Immune Response and Inflammation

The immune response is essential to protect organisms from infection and an altered self. An organism’s overall metabolic status is now recognized as an important and long-overlooked mediator of immunity and has spurred new explorations of immune-related metabolic abnormalities. Peroxisomes are essential metabolic organelles with a central role in the synthesis and turnover of complex lipids and reactive species. Peroxisomes have recently been identified as pivotal regulators of immune functions and inflammation in the development and during infection, defining a new branch of immunometabolism. This review summarizes the current evidence that has helped to identify peroxisomes as central regulators of immunity and highlights the peroxisomal proteins and metabolites that have acquired relevance in human pathologies for their link to the development of inflammation, neuropathies, aging and cancer. This review then describes how peroxisomes govern immune signaling strategies such as phagocytosis and cytokine production and their relevance in fighting bacterial and viral infections. The mechanisms by which peroxisomes either control the activation of the immune response or trigger cellular metabolic changes that activate and resolve immune responses are also described.

Isolating and culturing of sputum macrophages: A potential ex vivo/in vitro model

PURPOSE

This paper aimed to test whether induced sputum samples acquired from human volunteers could be used to isolate and culture airway macrophages for in vitro exposures. This was assessed in terms of the culturing success rate, culture purity, viability and responsiveness of cultured cells.

MATERIALS AND METHODS

The isolation and culturing procedure was performed over three days. On Day 1, induced sputum samples were obtained, processed and seeded in culture wells. Differential cell counts and viability tests were performed to allow for calculation of viable macrophage numbers and appropriate sample dilution. After a 1 h rest, seeded wells were washed to remove non-adherent cells, resulting in macrophage isolation. Then, cells rested overnight (Day 1-Day 2), before in vitro exposure for 2-24 h (Day 2-Day 3). The criteria for progressing into the culturing procedure was cell viability >40% and total cell number >10⁶. Successful culturing was evaluated based on cell attachment (N = 40). Culture purity by differential cell analysis and viability was monitored during culturing (N = 4-8). Macrophage responsivity was assessed by measurement of inflammatory cytokine gene expression (N = 4) and cytokine levels (N = 6) following in vitro exposure to lipopolysaccharide (LPS) (2-24 h) and live bacteria (S. aureus) (4h).

RESULTS

Overall, 88% (35/40) of the samples acquired were suitable for isolation, and 80% (32/40) were successfully progressed through the 2-3 day culturing protocol. Macrophage purity (88%) and viability (85%) were adequate. Moreover, cultured macrophages were responsive to in vitro stimulation with LPS and viable S. aureus showing positive mRNA responses for TNFα, IL-1β and IL-8 and release of IL-1β, respectively.

CONCLUSION

Sputum macrophage isolation by plate adherence and subsequent culturing of sputum macrophages was successfully performed and represents a promising in vitro model for examination of airway macrophage behavior.