Hydroxychloroquine is an antimalarial drug being tested as a potential treatment for the novel coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2. Although the efficacy of hydroxychloroquine for COVID-19 remains uncertain, it may serve as a potential prophylactic agent especially in those at high risk, such as healthcare workers, household contacts of infected patients, and the immunocompromised. Our aim was to identify possible hydroxychloroquine dosing regimens through simulation in those at high risk of infections by optimizing exposures above the in vitro generated half maximal effective concentration (EC 50 ) and to help guide researchers in dose-selection for COVID-19 prophylactic studies. To maintain weekly troughs above EC 50 in > 50% of subjects at steady-state in a pre-exposure prophylaxis setting, an 800 mg loading dose followed by 400 mg twice or 3 times weekly is required. In an exposure driven, postexposure prophylaxis setting, 800 mg loading dose followed in 6 hours by 600 mg, then 600 mg daily for 4 more days achieved daily troughs above EC 50 in > 50% subjects. These doses are higher than recommended for malaria chemoprophylaxis, and clinical trials are needed to establish safety and efficacy.

The lymphatic system maintains tissue homeostasis by transporting interstitial fluid, lipids and debris from tissues to the main circulation, and delivers antigen and antigen presenting cells to local lymph nodes where they elicit immune responses. During inflammation, lymph flow increases to limit edema and prevents tissue antigen-presenting cell transport. Lymphatics also adjust their contractile activity to increase fluid transfer during acute inflammation. Conversely, chronic inflammation can provoke lymphostasis, which might limit pathogen spread within the circulation; however, decreased lymph flow leads to the persistence of immune cells and mediators in tissues to intensifying injury. Here, we review lymphatic structure function within the gut, heart and central nervous system, discussing potential roles of these lymphatics in the etiology of inflammatory bowel disease, myocarditis and neurovascular disease, and as novel targets for therapeutic management of several disease states.

Theiler's murine encephalomyelitis virus (TMEV) induces different diseases in the central nervous system (CNS) and heart, depending on the mouse strains and time course, with cytokines playing key roles for viral clearance and immune-mediated pathology (immunopathology). In SJL/J mice, TMEV infection causes chronic TMEV-induced demyelinating disease (TMEV-IDD) in the spinal cord about 1 month post-inoculation (p.i.). Unlike other immunopathology models, both pro- and anti-inflammatory cytokines can play dual roles in TMEV-IDD. Pro-inflammatory cytokines play beneficial roles in viral clearance while they are also detrimental in immune-mediated demyelination. Anti-inflammatory cytokines suppress not only protective anti-viral immune responses but also detrimental autoreactive immune responses. Conversely, in C3H mice, TMEV infection induces a non-CNS disease, myocarditis, with three distinctive phases: phase I, viral pathology with interferon and chemokine responses; phase II, immunopathology mediated by acquired immune responses; and phase III, cardiac fibrosis. Although the exact mechanism(s) by which a single virus, TMEV, induces these different diseases in different organs is unclear, our bioinformatics approaches, especially principal component analysis (PCA) of transcriptome data, allow us to identify the key factors contributing to organ-specific immunopathology. The PCA demonstrated that in vitro infection of a cardiomyocyte cell line reproduced the transcriptome profile of phase I in TMEV-induced myocarditis; distinct interferon/chemokine-related responses were induced in vitro in TMEV-infected cardiomyocytes, but not in infected neuronal cells. In addition, the PCA of the in vivo CNS transcriptome data showed that decreased lymphatic marker expressions were weakly associated with inflammation in TMEV infection. Here, dysfunction of lymphatic vessels is shown to potentially contribute to immunopathology by delaying the clearance of cytokines and immune cells from the inflammatory site, although this can also confine the virus at these sites, preventing virus spread via lymphatic vessels. On the other hand, in the heart, dysfunction of lymphatics was associated with reduced lymphatic muscle contractility provoked by pro-inflammatory cytokines. Therefore, TMEV infection may induce different patterns of cytokine expressions as well as lymphatic vessel dysfunction by rather different mechanisms between the CNS and heart, which might explain observed patterns of organ-specific immunopathology.

Background and Purpose The lymphatic system maintains tissue homeostasis by unidirectional lymph flow, maintained by tonic and phasic contractions within subunits, ‘lymphangions’. Here we have studied the effects of the inflammatory cytokine IL‐1β on tonic contraction of rat mesenteric lymphatic muscle cells (RMLMC). Experimental Approach We measured IL‐1β in colon‐conditioned media (CM) from acute (AC‐CM, dextran sodium sulfate) and chronic (CC‐CM, T‐cell transfer) colitis‐induced mice and corresponding controls (Con‐AC/CC‐CM). We examined tonic contractility of RMLMC in response to CM, the cytokines h‐IL‐1β or h‐TNF‐α (5, 10, 20 ng·mL−1), with or without COX inhibitors [TFAP (10−5 M), diclofenac (0.2 × 10−5 M)], PGE2 (10−5 M)], IL‐1‐receptor antagonist, Anakinra (5 μg·mL−1), or a selective prostanoid EP4 receptor antagonist, GW627368X (10−6 and 10−7 M). Key Results Tonic contractility of RMLMC was reduced by AC‐ and CC‐CM compared with corresponding control culture media, Con‐AC/CC‐CM. IL‐1β or TNF‐α was not found in Con‐AC/CC‐CM, but detected in AC‐ and CC‐CM. h‐IL‐1β concentration‐dependently decreased RMLMC contractility, whereas h‐TNF‐α showed no effect. Anakinra blocked h‐IL‐1β‐induced RMLMC relaxation, and with AC‐CM, restored contractility to RMLMC. IL‐1β increased COX‐2 protein and PGE2 production in RMLMC.. PGE2 induced relaxations in RMLMC, comparable to h‐IL‐1β. Conversely, COX‐2 and EP4 receptor inhibition reversed relaxation induced by IL‐1β. Conclusions and Implications The IL‐1β‐induced decrease in RMLMC tonic contraction was COX‐2 dependent, and mediated by PGE2. In experimental colitis, IL‐1β and tonic lymphatic contractility were causally related, as this cytokine was critical for the relaxation induced by AC‐CM and pharmacological blockade of IL‐1β restored tonic contraction.

No abstract