Unraveling Links between Chronic Inflammation and Long COVID: Workshop Report.

As COVID-19 continues, an increasing number of patients develop long COVID symptoms varying in severity that last for weeks, months, or longer. Symptoms commonly include lingering loss of smell and taste, hearing loss, extreme fatigue, and "brain fog." Still, persistent cardiovascular and respiratory problems, muscle weakness, and neurologic issues have also been documented. A major problem is the lack of clear guidelines for diagnosing long COVID. Although some studies suggest that long COVID is due to prolonged inflammation after SARS-CoV-2 infection, the underlying mechanisms remain unclear. The broad range of COVID-19's bodily effects and responses after initial viral infection are also poorly understood. This workshop brought together multidisciplinary experts to showcase and discuss the latest research on long COVID and chronic inflammation that might be associated with the persistent sequelae following COVID-19 infection.

Metabolic Regulation of Inflammation and Its Resolution: Current Status, Clinical Needs, Challenges, and Opportunities.

Metabolism and inflammation have been viewed as two separate processes with distinct but critical functions for our survival: metabolism regulates the utilization of nutrients, and inflammation is responsible for defense and repair. Both respond to an organism's stressors to restore homeostasis. The interplay between metabolic status and immune response (immunometabolism) plays an important role in maintaining health or promoting disease development. Understanding these interactions is critical in developing tools for facilitating novel preventative and therapeutic approaches for diseases, including cancer. This trans-National Institutes of Health workshop brought together basic scientists, technology developers, and clinicians to discuss state-of-the-art, innovative approaches, challenges, and opportunities to understand and harness immunometabolism in modulating inflammation and its resolution.

Imaging inflammation and its resolution in health and disease: current status, clinical needs, challenges, and opportunities.

Inflammation is a normal process in our body; acute inflammation acts to suppress infections and support wound healing. Chronic inflammation likely leads to a wide range of diseases, including cancer. Tools to locate and monitor inflammation are critical for developing effective interventions to arrest inflammation and promote its resolution. To identify current clinical needs, challenges, and opportunities in advancing imaging-based evaluations of inflammatory status in patients, the U.S. National Institutes of Health convened a workshop on imaging inflammation and its resolution in health and disease. Clinical speakers described their needs for image-based capabilities that could help determine the extent of inflammatory conditions in patients to guide treatment planning and undertake necessary interventions. The imaging speakers showcased the state-of-the-art in vivo imaging techniques for detecting inflammation in different disease areas. Many imaging capabilities developed for 1 organ or disease can be adapted for other diseases and organs, whereas some have promise for clinical utility within the next 5-10 yr. Several speakers demonstrated that multimodal imaging measurements integrated with serum-based measures could improve in robustness for clinical utility. All speakers agreed that multiple inflammatory measures should be acquired longitudinally to comprehend the dynamics of unresolved inflammation that leads to disease development. They also agreed that the best strategies for accelerating clinical translation of imaging inflammation capabilities are through integration between new imaging techniques and biofluid-based biomarkers of inflammation as well as already established imaging measurements.-Liu, C. H., Abrams, N. D., Carrick, D. M., Chander, P., Dwyer, J., Hamlet, M. R. J., Kindzelski, A. L., PrabhuDas, M., Tsai, S.-Y. A., Vedamony, M. M., Wang, C., Tandon, P. Imaging inflammation and its resolution in health and disease: current status, clinical needs, challenges, and opportunities.

Structural and functional studies of FKHR-PAX3, a reciprocal fusion gene of the t(2;13) chromosomal translocation in alveolar rhabdomyosarcoma.

Alveolar rhabdomyosarcoma (ARMS) is an aggressive pediatric cancer of skeletal muscle. More than 70% of ARMS tumors carry balanced t(2;13) chromosomal translocation that leads to the production of two novel fusion genes, PAX3-FKHR and FKHR-PAX3. While the PAX3-FKHR gene has been intensely studied, the reciprocal FKHR-PAX3 gene has rarely been described. We report here the cloning and functional characterization of the FKHR-PAX3 gene as the first step towards a better understanding of its potential impact on ARMS biology. From RH30 ARMS cells, we detected and isolated three versions of FKHR-PAX3 cDNAs whose C-terminal sequences corresponded to PAX3c, PAX3d, and PAX3e isoforms. Unlike the nuclear-specific localization of PAX3-FKHR, the reciprocal FKHR-PAX3 proteins stayed predominantly in the cytoplasm. FKHR-PAX3 potently inhibited myogenesis in both non-transformed myoblast cells and ARMS cells. We showed that FKHR-PAX3 was not a classic oncogene but could act as a facilitator in oncogenic pathways by stabilizing PAX3-FKHR expression, enhancing cell proliferation, clonogenicity, anchorage-independent growth, and matrix adhesion in vitro, and accelerating the onset of tumor formation in xenograft mouse model in vivo. In addition to these pro-oncogenic behaviors, FKHR-PAX3 also negatively affected cell migration and invasion in vitro and lung metastasis in vivo. Taken together, these functional characteristics suggested that FKHR-PAX3 might have a critical role in the early stage of ARMS development.

Post-transcriptional regulation of PDGFα-receptor in O-2A progenitor cells.

latelet-derived growth factor alpha-receptor (PDGFαR) mediated signaling plays a key role in the development of glial cells of the central nervous system. In vivo and in vitro studies show that PDGFαR is actively expressed in proliferative and motile oligodendrocyte type-2 astrocyte (O-2A) glial progenitor cells. However, PDGFαR expression is barely detectable in mature glial cells. The exact mechanism underlying the loss of PDGFαR expression is unknown. In this study, we employed a rat brain-derived O-2A glial progenitor cell line, CG4 as a culture model to investigate signals capable of inhibiting PDGFαR gene expression. PDGFαR mRNA levels decreased significantly as CG4 cells differentiated into both oligodendrocyte and astrocyte lineages. We showed that inhibition of PDGFαR expression was promoted by prostaglandin E2 via protein kinase A activation. Both cAMP analogs (db-cAMP and 8'bromo-cAMP) and adenylate cyclase activator (forskolin) were potent suppressors of PDGFαR expression in CG4 cells. This inhibitory effect resulted from an increased destabilization of PDGFαR mRNA instead of a decreased PDGFαR gene transcription. Importantly, db-cAMP failed to reduce PDGFαR mRNA levels in several PDGFαR over-expressing human glioma cell lines. Together, these results suggest that cAMP-dependent pathway played a key regulatory role in controlling PDGFαR mRNA levels during normal glial development, and that a breakdown in the cross talk between cAMP and PDGF pathways may underlie the uncontrolled proliferation and immature differentiation state in the glial tumors.

Credentialing a preclinical mouse model of alveolar rhabdomyosarcoma.

The highly aggressive muscle cancer alveolar rhabdomyosarcoma (ARMS) is one of the most common soft tissue sarcoma of childhood, yet the outcome for the unresectable and metastatic disease is dismal and unchanged for nearly three decades. To better understand the pathogenesis of this disease and to facilitate novel preclinical approaches, we previously developed a conditional mouse model of ARMS by faithfully recapitulating the genetic mutations observed in the human disease, i.e., activation of Pax3:Fkhr fusion gene with either p53 or Cdkn2a inactivation. In this report, we show that this model recapitulates the immunohistochemical profile and the rapid progression of the human disease. We show that Pax3:Fkhr expression increases during late preneoplasia but tumor cells undergoing metastasis are under apparent selection for Pax3:Fkhr expression. At a whole-genome level, a cross-species gene set enrichment analysis and metagene projection study showed that our mouse model is most similar to human ARMS when compared with other pediatric cancers. We have defined an expression profile conserved between mouse and human ARMS, as well as a Pax3:Fkhr signature, including the target gene, SKP2. We further identified 7 "druggable" kinases overexpressed across species. The data affirm the accuracy of this genetically engineered mouse model.

Comparative analysis of paired- and homeodomain-specific roles in PAX3-FKHR oncogenesis.

The alveolar rhabdomyosarcoma-associated t(2;13) chromosomal translocation produces an oncogenic fusion transcription factor PAX3-FKHR that combines the N-terminal DNA binding domains (paired domain and homeodomain) of PAX3 with the C-terminal activation domain of FKHR. In the context of PAX3-FKHR, the two DNA binding domains can work either cooperatively or autonomously in regulating gene transcription. The latter is a gain-of-function unique to the fusion protein. The biological activities driven by the individual DNA binding domain remains poorly defined. In this study, we express PAX3-FKHR mutants that contain only a single functional DNA binding domain into C2C12 myoblasts, and measured the in vitro and in vivo behaviors of these cells. We show that only the homeodomain-specific PAX3-FKHR mutant recapitulates the in vitro transformation properties of the wild type fusion protein. However, despite the differential responses in vitro, both the paired domain- and the homeodomain-specific PAX3-FKHR mutants promote tumor development from myoblasts in vivo. Our results suggest an important role for the gain of the paired domain- and the homeodomain-transcription activities in the PAX3-FKHR malignant transformation process.

PAX3-FKHR transformation increases 26 S proteasome-dependent degradation of p27Kip1, a potential role for elevated Skp2 expression.

PAX3-FKHR is an oncogenic form of the developmental regulator Pax3 transcription factor. PAX3-FKHR results from a t(2,13) chromosomal translocation, a unique genetic marker of alveolar rhabdomyosarcoma. In this study, we showed that ectopic expression of PAX3-FKHR, but not Pax3, in fibroblasts altered cell cycle control and accelerated G(0)/G(1) to S cell cycle transition. PAX3-FKHR-expressing cells had reduced expression of p27(Kip1) protein, a key cell cycle regulator. The reduction in p27(Kip1) levels by PAX3-FKHR resulted from destabilization of p27(Kip1) as shown by cycloheximide treatment and in vivo pulse-chase labeling experiments. The reduced p27(Kip1) protein level in PAX3-FKHR-expressing cells was restored to the level of control cells by treatment with chemical inhibitors that specifically blocked 26 S proteasome activity. Along with the reduction in p27(Kip1) protein, PAX3-FKHR-expressing cells exhibited elevated expression of F-box Skp2 protein, a substrate-specific component of SCF (Skp1-Cullin-F box protein) ligase involved in the cell cycle-dependent control of p27(Kip1) ubiquitination and 26 S proteasome dependent degradation. Finally, we showed that ectopic expression of p27(Kip1) in PAX3-FKHR-expressing cells significantly reduced the proliferation and colony-forming potential of these cells, implicating that down-regulation of p27(Kip1) protein played an active role in the PAX3-FKHR-directed cell transformation.