Androgens and estrogens are known to be critical regulators of mammalian physiology and development. While these two classes of steroids share similar structures (in general, estrogens are derived from androgens via the enzyme aromatase), they subserve markedly different functions via their specific receptors. In the past, estrogens such as estradiol were thought to be most important in the regulation of female biology, while androgens such as testosterone and dihydrotestosterone were believed to primarily modulate development and physiology in males. However, the emergence of patients with deficiencies in androgen or estrogen hormone synthesis or actions, as well as the development of animal models that specifically target androgen- or estrogen-mediated signaling pathways, have revealed that estrogens and androgens regulate critical biological and pathological processes in both males and females. In fact, the concept of “male” and “female” hormones is an oversimplification of a complex developmental and biological network of steroid actions that directly impacts many organs. In this Review, we will discuss important roles of estrogens in males and androgens in females.
Stephen R. Hammes, Ellis R. Levin
Graft-versus-host disease (GvHD) is a common complication of hematopoietic cell transplantation that negatively impacts quality of life in recipients and can be fatal. Animal experiments and human studies provide compelling evidence that the gut microbiota is associated with risk of GvHD, but the nature of this relationship remains unclear. If the gut microbiota is a driver of GvHD pathogenesis, then manipulation of the gut microbiota offers one promising avenue for preventing or treating this common condition, and antibiotic stewardship efforts in transplantation may help preserve the indigenous microbiota and modulate immune responses to benefit the host.
David N. Fredricks
Oncolytic virotherapy (OVT) is a promising approach in which WT or engineered viruses selectively replicate and destroy tumor cells while sparing normal ones. In the last two decades, different oncolytic viruses (OVs) have been modified and tested in a number of preclinical studies, some of which have led to clinical trials in cancer patients. These clinical trials have revealed several critical limitations with regard to viral delivery, spread, resistance, and antiviral immunity. Here, we focus on promising research strategies that have been developed to overcome the aforementioned obstacles. Such strategies include engineering OVs to target a broad spectrum of tumor cells while evading the immune system, developing unique delivery mechanisms, combining other immunotherapeutic agents with OVT, and using clinically translatable mouse tumor models to potentially translate OVT more readily into clinical settings.
Jordi Martinez-Quintanilla, Ivan Seah, Melissa Chua, Khalid Shah
The rapid expansion in the number of encephalitis disorders associated with autoantibodies against neuronal proteins has led to an incremental increase in use of the term “autoimmune epilepsy,” yet has occurred with limited attention to the physiopathology of each disease and genuine propensity to develop epilepsy. Indeed, most autoimmune encephalitides present with seizures, but the probability of evolving to epilepsy is relatively small. The risk of epilepsy is higher for disorders in which the antigens are intracellular (often T cell–mediated) compared with disorders in which the antigens are on the cell surface (antibody-mediated). Most autoantibodies against neuronal surface antigens show robust effects on the target proteins, resulting in hyperexcitability and impairment of synaptic function and plasticity. Here, we trace the evolution of the concept of autoimmune epilepsy and examine common inflammatory pathways that might lead to epilepsy. Then, we focus on several antibody-mediated encephalitis disorders that associate with seizures and review the synaptic alterations caused by patients’ antibodies, with emphasis on those that have been modeled in animals (e.g., antibodies against NMDA, AMPA receptors, LGI1 protein) or in cultured neurons (e.g., antibodies against the GABAb receptor).
Christian Geis, Jesus Planagumà, Mar Carreño, Francesc Graus, Josep Dalmau
Antisense oligonucleotides (ASOs) are chemically synthesized nucleic acid analogs designed to bind to RNA by Watson-Crick base pairing. Following binding to the targeted RNA, the ASO perturbs RNA function by promoting selective degradation of the targeted RNA, altering RNA intermediary metabolism, or disrupting function of the RNA. Most antisense drugs are chemically modified to enhance their pharmacological properties and for passive targeting of the tissues of therapeutic interest. Recent advances in selective tissue targeting have resulted in a newer generation of ASO drugs that are more potent and better tolerated than previous generations, spawning renewed interest in identifying selective ligands that enhance targeted delivery of ASOs to tissues.
Punit P. Seth, Michael Tanowitz, C. Frank Bennett
Although platelets are best known for their role in hemostasis, they are also crucial in development, host defense, inflammation, and tissue repair. Many of these roles are regulated by the immune-like receptors glycoprotein VI (GPVI) and C-type lectin receptor 2 (CLEC-2), which signal through an immunoreceptor tyrosine–based activation motif (ITAM). GPVI is activated by collagen in the subendothelial matrix, by fibrin and fibrinogen in the thrombus, and by a remarkable number of other ligands. CLEC-2 is activated by the transmembrane protein podoplanin, which is found outside of the vasculature and is upregulated in development, inflammation, and cancer, but there is also evidence for additional ligands. In this Review, we discuss the physiological and pathological roles of CLEC-2 and GPVI and their potential as targets in thrombosis and thrombo-inflammatory disorders (i.e., disorders in which inflammation plays a critical role in the ensuing thrombosis) relative to current antiplatelet drugs.
Julie Rayes, Steve P. Watson, Bernhard Nieswandt
Donor age and recipient age are factors that influence transplantation outcomes. Aside from age-associated differences in intrinsic graft function and alloimmune responses, the ability of young and old cells to exert either rejuvenating or aging effects extrinsically may also apply to the transplantation of hematopoietic stem cells or solid organ transplants. While the potential for rejuvenation mediated by the transfer of youthful cells is currently being explored for therapeutic applications, aspects that relate to accelerating aging are no less clinically significant. Those effects may be particularly relevant in transplantation with an age discrepancy between donor and recipient. Here, we review recent advances in understanding the mechanisms by which young and old cells modify their environments to promote rejuvenation- or aging-associated phenotypes. We discuss their relevance to clinical transplantation and highlight potential opportunities for therapeutic intervention.
Ashley Lau, Brian K. Kennedy, James L. Kirkland, Stefan G. Tullius
Fibrosis, the progressive accumulation of connective tissue that occurs in response to injury, causes irreparable organ damage and may result in organ failure. The few available antifibrotic treatments modify the rate of fibrosis progression, but there are no available treatments to reverse established fibrosis. Thus, more effective therapies are urgently needed. Molecular imaging is a promising biomedical methodology that enables noninvasive visualization of cellular and subcellular processes. It provides a unique means to monitor and quantify dysregulated molecular fibrotic pathways in a noninvasive manner. Molecular imaging could be used for early detection, disease staging, and prognostication, as well as for assessing disease activity and treatment response. As fibrotic diseases are often molecularly heterogeneous, molecular imaging of a specific pathway could be used for patient stratification and cohort enrichment with the goal of improving clinical trial design and feasibility and increasing the ability to detect a definitive outcome for new therapies. Here we review currently available molecular imaging probes for detecting fibrosis and fibrogenesis, the active formation of new fibrous tissue, and their application to models of fibrosis across organ systems and fibrotic processes. We provide our opinion as to the potential roles of molecular imaging in human fibrotic diseases.
Sydney B. Montesi, Pauline Désogère, Bryan C. Fuchs, Peter Caravan
Mitochondrial respiratory deficiencies have been observed in numerous neurodegenerative disorders, such as Alzheimer’s and Parkinson’s diseases. For decades, these reductions in oxidative phosphorylation (OxPhos) have been presumed to trigger an overall bioenergetic crisis in the neuron, resulting in cell death. While the connection between respiratory defects and neuronal death has never been proven, this hypothesis has been supported by the detection of nonspecific mitochondrial DNA mutations in these disorders. These findings led to the notion that mitochondrial respiratory defects could be initiators of these common neurodegenerative disorders, instead of being consequences of a prior insult, a theory we believe to be misconstrued. Herein, we review the roots of this mitochondrial hypothesis and offer a new perspective wherein mitochondria are analyzed not only from the OxPhos point of view, but also as a complex organelle residing at the epicenter of many metabolic pathways.
Estela Area-Gomez, Cristina Guardia-Laguarta, Eric A. Schon, Serge Przedborski
A complex DNA repair machinery has evolved to protect genomic integrity in the face of a myriad of DNA damage sources. When DNA repair fails, this damage can lead to carcinogenesis and tumor genomic instability. Indeed, many heritable cancer predisposition syndromes are attributable to germline defects in DNA repair pathways. On the other hand, these defects may also portend particular vulnerabilities of the cancer and may be exploited therapeutically. Most recently this has been demonstrated in the case of mismatch repair-deficient cancers, in which the immune checkpoint inhibitors have been demonstrated to be highly active. This observation has paved the way for further research investigating other sources of genomic instability that may serve as biomarkers to select patients for immunotherapy.
Katherine M. Bever, Dung T. Le
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