Macrophage phagocytosis of SARS-CoV-2-infected cells mediates potent plasmacytoid dendritic cell activation

Early and strong interferon type I (IFN-I) responses are usually associated with mild COVID-19 disease, whereas persistent or unregulated proinflammatory cytokine responses are associated with severe disease outcomes. Previous work suggested that monocyte-derived macrophages (MDMs) are resistant and unresponsive to SARS-CoV-2 infection. Here, we demonstrate that upon phagocytosis of SARS-CoV-2-infected cells, MDMs are activated and secrete IL-6 and TNF. Importantly, activated MDMs in turn mediate strong activation of plasmacytoid dendritic cells (pDCs), leading to the secretion of high levels of IFN-α and TNF. Furthermore, pDC activation promoted IL-6 production by MDMs. This kind of pDC activation was dependent on direct integrin-mediated cell‒cell contacts and involved stimulation of the TLR7 and STING signaling pathways. Overall, the present study describes a novel and potent pathway of pDC activation that is linked to the macrophage-mediated clearance of infected cells. These findings suggest that a high infection rate by SARS-CoV-2 may lead to exaggerated cytokine responses, which may contribute to tissue damage and severe disease.

Phase locking of lasers with self-stabilized minimal coupling

A novel configuration for phase locking two ring lasers with self-stabilized minimal exchange of power between them is presented. We show experimentally that losses introduced between the lasers are self compensated in order to maintain minimal power exchange between them. The experimental results are in good agreement with numerical results.

[Severe drug hypersensitivity reaction (DRESS syndrome) to doxycycline]

BACKGROUND

While many cases of DRESS reaction to minocycline have been described, few of these involve doxycycline.

CASE STUDY

A 59-year-old woman of African origin was repatriated after a journey to Ghana for hyperthermia with infiltrated maculopapular exanthema, facial oedema (no mucosal involvement) and polyadenopathy. Laboratory tests revealed hypereosinophilia, hepatic cytolysis and mononucleosis syndrome. Cutaneous histology was non-specific. The patient had been taking doxycycline as antimalarial prophylaxis for three weeks before the onset of symptoms. DRESS to doxycycline was diagnosed. Patch-tests with doxycycline three months later proved negative. The patient's HLA phenotype was A3/A30 and B39/B42.

DISCUSSION

An intrinsic causal relationship with doxycycline was likely in this case (I3). Although patch-test sensitivity and specificity with doxycycline remains unknown in DRESS exploration, a negative result does not necessarily rule out the diagnosis. A number of cases of DRESS to doxycycline have been described recently, possibly as a result of more frequent prescription (malarial prophylaxis, acne). Subjects of African ethnicity or having specific HLA phenotypes are at higher risk of developing drug hypersensitivity.

CONCLUSION

This patient is the third case of DRESS to doxycycline described in the literature. The originality of this case lies in the allergological investigation using patch-tests and HLA determination.

P-glycoprotein-mediated transport of digitoxin, alpha-methyldigoxin and beta-acetyldigoxin

Digoxin is a drug with a narrow therapeutic index, which is substrate of the ATP-dependent efflux pump P-glycoprotein. Increased or decreased digoxin plasma concentrations occur in humans due to inhibition or induction of this drug transporter in organs with excretory function such as small intestine, liver and kidneys. Whereas particle size, dissolution rate and lipophilic properties have been identified as determinants for absorption of digitalis glycosides, little is known about P-glycoprotein transport characteristics of digitalis glycosides such as digitoxin, alpha-methyldigoxin, beta-acetyldigoxin and ouabain. Using polarized P-glycoprotein-expressing cell lines we therefore studied whether these compounds are substrates of P-glycoprotein. Polarized transport of digitalis glycosides was assessed in P-glycoprotein-expressing Caco-2 and L-MDR1 cells (LLC-PK1 cells stably transfected with the human MDR1 P-glycoprotein). Inhibition of P-glycoprotein-mediated transport of these compounds in Caco-2 cells was determined using the cyclosporine analogue PSC-833 (valspodar) as inhibitor of P-glycoprotein. No polarized transport was observed for ouabain. However, basal-to-apical transport of digitoxin, alpha-methyldigoxin and beta-acetyldigoxin was greater than apical-to-basal transport in Caco-2 and L-MDR1 cells. In Caco-2 cells net transport rates of these compounds were similar to those of digoxin (digoxin: 16.0+/-4.4%, digitoxin: 15.0+/-3.3%, beta-acetyldigoxin: 16.2+/-1.6%, alpha-methyldigoxin: 13.5+/-4.8%). Furthermore, polarized transport of these compounds could be completely inhibited by 1 microM PSC-833. In summary, these data provide evidence that not only digoxin, but also digitoxin, alpha-methyldigoxin and beta-acetyldigoxin are substrates of P-glycoprotein.