ABSTRACT
BACKGROUND: Hereditary hemorrhagic telangiectasia (HHT) is a vascular bleeding disorder characterized by mucocutaneous telangiectasias and visceral arteriovenous malformations. A frequently debilitating symptom is spontaneous recurrent epistaxis. OBJECTIVE: To evaluate whether doxycycline therapy improves epistaxis in HHT by using a prospective, randomized, placebo-controlled crossover study design. PATIENTS/METHODS: Twenty-two eligible patients between December 2017 and July 2020 at a single center were randomized to one of two study arms: doxycycline treatment followed by placebo, or vice versa. Primary outcomes measured differences in epistaxis severity between treatments. Changes in quality of life, laboratory markers of bleeding, and number of monthly blood transfusions or iron infusions were assessed as secondary endpoints. Additional post hoc endpoints included frequency and duration of dripping epistaxis and gushing epistaxis. A post hoc longitudinal analysis assessed effects of doxycycline over time. RESULTS/CONCLUSIONS: Doxycycline was safe and well tolerated. However, there was no reduction in the three primary outcome measures, nosebleed frequency (p = .16), nosebleed duration (p = .05), and Epistaxis Severity Score (p = .19). Quality of life, hemoglobin level, and number of blood transfusions and iron infusions did not differ between groups. Post hoc analysis demonstrated reduction in instances of gushing (p = .02) with doxycycline, although this finding is of unclear clinical significance. Post hoc longitudinal analysis showed reduction in frequency (mean estimate of coefficient = -0.19, standard error = 0.07, p = .01) and duration (mean estimate of coefficient = -2.33, standard error = 1.08, p = .03) of epistaxis over time. Post hoc findings suggest possible benefit of doxycycline but should be interpreted with caution given the overall negative study. Further investigation is needed with a larger sample size and a longer treatment duration.
Subject(s)
Epistaxis , Telangiectasia, Hereditary Hemorrhagic , Cross-Over Studies , Doxycycline/adverse effects , Epistaxis/diagnosis , Epistaxis/drug therapy , Humans , Iron , North America , Prospective Studies , Quality of Life , Telangiectasia, Hereditary Hemorrhagic/complications , Telangiectasia, Hereditary Hemorrhagic/diagnosis , Telangiectasia, Hereditary Hemorrhagic/drug therapy , Treatment OutcomeABSTRACT
The Arabidopsis thaliana resistance gene RPW8 triggers the hypersensitive response (HR) to restrict powdery mildew infection via the salicylic acid-dependent signaling pathway. To further understand how RPW8 signaling is regulated, we have conducted a genetic screen to identify mutations enhancing RPW8-mediated HR-like cell death (designated erh). Here, we report the isolation and characterization of the Arabidopsis erh1 mutant, in which the At2g37940 locus is knocked out by a T-DNA insertion. Loss of function of ERH1 results in salicylic acid accumulation, enhanced transcription of RPW8 and RPW8-dependent spontaneous HR-like cell death in leaf tissues, and reduction in plant stature. Sequence analysis suggests that ERH1 may encode the long-sought Arabidopsis functional homolog of yeast and protozoan inositolphosphorylceramide synthase (IPCS), which converts ceramide to inositolphosphorylceramide. Indeed, ERH1 is able to rescue the yeast aur1 mutant, which lacks the IPCS, and the erh1 mutant plants display reduced ( approximately 53% of wild type) levels of leaf IPCS activity, indicating that ERH1 encodes a plant IPCS. Consistent with its biochemical function, the erh1 mutation causes ceramide accumulation in plants expressing RPW8. These data reinforce the concept that sphingolipid metabolism (specifically, ceramide accumulation) plays an important role in modulating plant programmed cell death associated with defense.
Subject(s)
Arabidopsis Proteins/metabolism , Arabidopsis/enzymology , Cell Death , Hexosyltransferases/metabolism , Arabidopsis/genetics , Arabidopsis/physiology , Arabidopsis Proteins/genetics , Ascomycota , Cloning, Molecular , DNA, Bacterial/genetics , Gene Expression Regulation, Plant , Hexosyltransferases/genetics , Molecular Sequence Data , Mutagenesis , Mutation , Phenotype , Plants, Genetically Modified/enzymology , Plants, Genetically Modified/genetics , Plants, Genetically Modified/physiology , RNA, Plant/genetics , Sequence Homology, Amino Acid , Transcription, GeneticABSTRACT
The RPW8 locus of Arabidopsis thaliana confers broad-spectrum resistance to powdery mildew pathogens. In many A. thaliana accessions, this locus contains two homologous genes, RPW8.1 and RPW8.2. In some susceptible accessions, however, these two genes are replaced by HR4, a homolog of RPW8.1. Here, we show that RPW8.2 from A. lyrata conferred powdery mildew resistance in A. thaliana, suggesting that RPW8.2 might have gained the resistance function before the speciation of A. thaliana and A. lyrata. To investigate how RPW8 has been maintained in A. thaliana, we examined the nucleotide sequence polymorphisms in RPW8 from 51 A. thaliana accessions, related disease reaction phenotypes to the evolutionary history of RPW8.1 and RPW8.2, and identified mutations that confer phenotypic variations. The average nucleotide diversities were high at RPW8.1 and RPW8.2, showing no sign of selective sweep. Moreover, we found that expression of RPW8 incurs fitness benefits and costs on A. thaliana in the presence and absence of the pathogens, respectively. Our results suggest that polymorphisms at the RPW8 locus in A. thaliana may have been maintained by complex selective forces, including those from the fitness benefits and costs both associated with RPW8.
