Development of Highly Potent, G-Protein Pathway Biased, Selective, and Orally Bioavailable GPR84 Agonists.

Orphan G-protein-coupled receptor 84 (GPR84) is a receptor that has been linked to cancer, inflammatory, and fibrotic diseases. We have reported DL-175 as a biased agonist at GPR84 which showed differential signaling via Gαi/cAMP and ß-arrestin, but which is rapidly metabolized. Herein, we describe an optimization of DL-175 through a systematic structure-activity relationship (SAR) analysis. This reveals that the replacement of the naphthalene group improved metabolic stability and the addition of a 5-hydroxy substituent to the pyridine N-oxide group, yielding compounds 68 (OX04528) and 69 (OX04529), enhanced the potency for cAMP signaling by 3 orders of magnitude to low picomolar values. Neither compound showed detectable effects on ß-arrestin recruitment up to 80 µM. Thus, the new GPR84 agonists 68 and 69 displayed excellent potency, high G-protein signaling bias, and an appropriate in vivo pharmacokinetic profile that will allow investigation of GPR84 biased agonist activity in vivo.

A KLK6 Activity-Based Probe Reveals a Role for KLK6 Activity in Pancreatic Cancer Cell Invasion.

Pancreatic cancer has the lowest survival rate of all common cancers due to late diagnosis and limited treatment options. Serine hydrolases are known to mediate cancer progression and metastasis through initiation of signaling cascades and cleavage of extracellular matrix proteins, and the kallikrein-related peptidase (KLK) family of secreted serine proteases have emerging roles in pancreatic ductal adenocarcinoma (PDAC). However, the lack of reliable activity-based probes (ABPs) to profile KLK activity has hindered progress in validation of these enzymes as potential targets or biomarkers. Here, we developed potent and selective ABPs for KLK6 by using a positional scanning combinatorial substrate library and characterized their binding mode and interactions by X-ray crystallography. The optimized KLK6 probe IMP-2352 (kobs/I = 11,000 M-1 s-1) enabled selective detection of KLK6 activity in a variety of PDAC cell lines, and we observed that KLK6 inhibition reduced the invasiveness of PDAC cells that secrete active KLK6. KLK6 inhibitors were combined with N-terminomics to identify potential secreted protein substrates of KLK6 in PDAC cells, providing insights into KLK6-mediated invasion pathways. These novel KLK6 ABPs offer a toolset to validate KLK6 and associated signaling partners as targets or biomarkers across a range of diseases.

20 Years an Orphan: Is GPR84 a Plausible Medium-Chain Fatty Acid-Sensing Receptor?

GPR84 is an inflammation-induced receptor highly expressed on immune cells, yet its endogenous ligand is still unknown. This makes any interpretation of its physiological activity in vivo difficult. However, experiments with potent synthetic agonists have highlighted what the receptor can do, namely, enhance proinflammatory signaling and macrophage effector functions such as phagocytosis. Developing drugs to block these effects has attracted interest from the scientific community with the aim of decreasing disease activity in inflammatory disorders or enhancing inflammation resolution. In this review, we critically reassess the widely held belief that the major role of GPR84 is that of being a medium-chain fatty acid (MCFA) receptor. While MCFAs have been shown to activate GPR84, it remains to be demonstrated that they are present in relevant tissues at appropriate concentrations. In contrast to four other "full-time" free fatty acid receptor subtypes, GPR84 is not expressed by enteroendocrine cells and has limited expression in the gastrointestinal tract. Across multiple tissues and cell types, the highest expression levels of GPR84 are observed hours after exposure to an inflammatory stimulus. These factors obscure the relationship between ligand and receptor in the human body and do not support the exclusive physiological pairing of MCFAs with GPR84. To maximize the chances of developing efficacious drugs for inflammatory diseases, we must advance our understanding of GPR84 and what it does in vivo.

A Natural Product Puts Malaria on a Low-Fat Diet.

In this issue of Cell Chemical Biology, Yoo et al. (2020) use chemical proteomics to identify target proteins for the potent antimalarial natural product Salinipostin A. Polypharmacology from targeting multiple parasite serine hydrolases and lipases limits resistance to the compound, making this a promising new approach for treating malaria.

A Biased Agonist at Immunometabolic Receptor GPR84 Causes Distinct Functional Effects in Macrophages.

GPR84 is an orphan G-protein-coupled receptor that is expressed on immune cells and implicated in several inflammatory diseases. The validation of GPR84 as a therapeutic target is hindered by the narrow range of available chemical tools and consequent poor understanding of GPR84 pathophysiology. Here we describe the discovery and characterization of DL-175, a potent, selective, and structurally novel GPR84 agonist and the first to display significantly biased signaling across GPR84-overexpressing cells, primary murine macrophages, and human U937 cells. By comparing DL-175 with reported GPR84 ligands, we show for the first time that biased GPR84 agonists have markedly different abilities to induce chemotaxis in human myeloid cells, while causing similar levels of phagocytosis enhancement. This work demonstrates that biased agonism at GPR84 enables the selective activation of functional responses in immune cells and delivers a high-quality chemical probe for further investigation.

Activation of the Immune-Metabolic Receptor GPR84 Enhances Inflammation and Phagocytosis in Macrophages.

GPR84 is a member of the metabolic G protein-coupled receptor family, and its expression has been described predominantly in immune cells. GPR84 activation is involved in the inflammatory response, but the mechanisms by which it modulates inflammation have been incompletely described. In this study, we investigated GPR84 expression, activation, and function in macrophages to establish the role of the receptor during the inflammatory response. We observed that GPR84 expression in murine tissues is increased by endotoxemia, hyperglycemia, and hypercholesterolemia. Ex vivo studies revealed that GPR84 mRNA expression is increased by LPS and other pro-inflammatory molecules in different murine and human macrophage populations. Likewise, high glucose concentrations and the presence of oxidized LDL increased GPR84 expression in macrophages. Activation of the GPR84 receptor with a selective agonist, 6-(octylamino) pyrimidine-2,4(1H,3H)-dione (6-n-octylaminouracil, 6-OAU), enhanced the expression of phosphorylated Akt, p-ERK, and p65 nuclear translocation under inflammatory conditions and elevated the expression levels of the inflammatory mediators TNFα, IL-6, IL-12B, CCL2, CCL5, and CXCL1. In addition, GPR84 activation triggered increased bacterial adhesion and phagocytosis in macrophages. The enhanced inflammatory response mediated by 6-OAU was not observed in GPR84-/- cells nor in macrophages treated with a selective GPR84 antagonist. Collectively, our results reveal that GPR84 functions as an enhancer of inflammatory signaling in macrophages once inflammation is established. Therefore, molecules that antagonize the GPR84 receptor may be potential therapeutic tools in inflammatory and metabolic diseases.

The Role of Metabolite-Sensing G Protein-Coupled Receptors in Inflammation and Metabolic Disease.

SIGNIFICANCE: Great attention has been placed on the link between metabolism and immune function giving rise to the term "immunometabolism." It is widely accepted that inflammation and oxidative stress are key processes that underlie metabolic complications during obesity, diabetes, and atherosclerosis. Therefore, identifying the mechanisms and mediators that are involved in the regulation of both inflammation and metabolic homeostasis is of high scientific and therapeutic interest. Recent Advances: G protein-coupled receptors (GPCRs) that signal in response to metabolites have emerged as attractive therapeutic targets in inflammatory disease. Critical Issues and Future Directions: In this review, we discuss recent findings about the physiological role of the main metabolite-sensing GPCRs, their implication in immunometabolic disorders, their principal endogenous and synthetic ligands, and their potential as drug targets in inflammation and metabolic disease. Antioxid. Redox Signal. 29, 237-256.

Lipodystrophy syndrome associated with antiretroviral therapy in HIV patients: considerations for psychosocial aspects.

Several side effects have been strongly associated with antiretroviral therapy in HIV patients. Among them, the lipodystrophy syndrome which presents alterations in body shape with central adipose hypertrophy and peripheral lipoatrophy, reported by patients as a visible marker identifying them as HIV patients. This manuscript presents an analysis of current literature regarding the psychosocial aspects of HIV patients with lipodystrophy associated with antiretroviral therapy. The results show that the alterations in body shape can be disturbing in terms of psychosocial well being, affecting quality of life and increasing the stigma associated with the disease, with consequent disturbances in social relations. This analysis provides a preliminary review of the psychosocial aspects of lipodystrophy and further studies are needed for a better understanding of this complex syndrome, which could provide new information to be used in nursing care for HIV patients affected by this problem.

Lipodystrophy syndrome associated with antiretroviral therapy in HIV patients: considerations for psychosocial aspects: [review] / Síndrome de la lipodistrofia asociado con la terapia antiretroviral en pacientes con VIH: consideraciones para los aspectos psicosociales: [revisión] / Sindrome da lipodistrofia associada com a terapia anti-retroviral em portadores do HIV: considerações para os aspectos psicossociais: [revisão]

Several side effects have been strongly associated with antiretroviral therapy in HIV patients. Among them, the lipodystrophy syndrome which presents alterations in body shape with central adipose hypertrophy and peripheral lipoatrophy, reported by patients as a visible marker identifying them as HIV patients. This manuscript presents an analysis of current literature regarding the psychosocial aspects of HIV patients with lipodystrophy associated with antiretroviral therapy. The results show that the alterations in body shape can be disturbing in terms of psychosocial well being, affecting quality of life and increasing the stigma associated with the disease, with consequent disturbances in social relations. This analysis provides a preliminary review of the psychosocial aspects of lipodystrophy and further studies are needed for a better understanding of this complex syndrome, which could provide new information to be used in nursing care for HIV patients affected by this problem.

Varios efectos secundarios han sido fuertemente asociados con la terapia antiretroviral en pacientes con HIV. Entre ellos, el síndrome de la lipodistrofia se presenta con alteraciones en la forma del cuerpo con hipertrofia adiposa central y lipoatrofia periférica, las cuales son reportadas por pacientes como marcas visibles que los identifica como pacientes con VIH. En este manuscrito, presentamos un análisis de literatura actual con respecto a los aspectos psicosociales de pacientes con VIH presentándose con lipodistrofia asociado con la terapia antiretroviral. Los resultados demuestran que las alteraciones de la forma del cuerpo pueden ser inquietantes en lo que se refiere al bienestar psicosocial, afectando la calidad de vida y aumentando el estigma asociado con la enfermedad, con las consiguientes dificultades en las relaciones sociales. Este análisis provee un repaso preliminar de los aspectos psicosociales de la lipodistrofia; sin embargo, otros estudios son necesarios para entender mejor este complejo síndrome, proveyendo nueva información para ser utilizada en el cuidado de enfermería para pacientes con VIH que están afectados por este problema.

Diversos efeitos colaterais têm sido associados à terapia anti-retroviral em portadores da infecção pelo HIV, dentre esses, a síndrome da lipodistrofia apresentando hiperlipidemia e alterações na forma do corpo, com hipertrofia adiposa central e lipoatrofia periférica, relatada pelos pacientes como um visível marcador para a identificação de portadores da infecção pelo HIV. Este estudo consiste em análise da produção científica sobre aspectos psicossociais em portadores da infecção pelo HIV que apresentam lipodistrofia associada à utilização da terapia anti-retroviral. Os resultados mostram que alterações corporais podem ser suficientemente perturbadoras para o bem-estar psicossocial, afetando a qualidade de vida e aumentando o estigma da doença, ocasionando perturbações nas relações sociais. Esta revisão possibilita uma análise preliminar dos aspectos psicossocias da lipodistrofia; entretanto, outros estudos são necessários para o melhor entendimento desta complexa síndrome, trazendo novas informações a serem utilizadas no cuidado de enfermagem a portadores da infecção pelo HIV afetados por este problema.