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Histamine H1-receptor-mediated calcium influx in DDT1MF-2 cells.

ABSTRACT: Undifferentiated monolayers of the hamster vas deferens smooth-muscle cell line, DDT1MF-2, were grown on glass coverslips and loaded with the Ca(2+)-sensitive fluorescent dye fura-2. Stimulation with histamine produced a rapid and maintained increase in intracellular free Ca2+ ([Ca2+]i), with an EC50 of 7.0 +/- 0.7 microM. The initial rise in [Ca2+]i can be attributed to Ca2+ release from intracellular stores, whereas the maintained or plateau phase is due to influx of extracellular Ca2+. The Ca2+ influx associated with the plateau phase required the continued presence of histamine on the receptor, since the H1-antagonist mepyramine (10 microM) attenuated the rise in [Ca2+]i observed when extracellular Ca2+ was re-applied after the cells had been stimulated with histamine, in experiments performed in nominally Ca(2+)-free buffer. Pretreatment with the inorganic Ca(2+)-channel blockers Ni2+ (1 mM) and Co2+ (1 mM) inhibited the influx component, whereas the organic voltage-operated Ca(2+)-channel antagonists nifedipine (10 microM) and PN-200-110 (10 microM) had no effect. These data suggest that histamine stimulates Ca2+ influx through an H1-receptor-activated Ca2+ channel. Experiments with Mn2+ indicated that the receptor-mediated Ca(2+)-influx pathway(s) is impermeable to Mn2+. Furthermore, the refilling of Ca2+ stores can occur independently of H1-receptor-mediated influx, since store refilling can be demonstrated even when the receptor-mediated Ca2+ entry is blocked by mepyramine. In conclusion, H1-receptor activation in the smooth-muscle cell line DDT1MF-2 stimulates both release of Ca2+ from intracellular stores [inositol 1,4,5-triphosphate (InsP3)-mediated] and Ca2+ influx through a receptor-activated Ca2+ channel. The subsequent refilling of the InsP3-sensitive intracellular Ca2+ store is independent of histamine H1-receptor stimulation (mepyramine-insensitive) and occurs without an observable rise in cytosolic free Ca2+.

SUBMITTER: Dickenson JM

PROVIDER: S-EPMC1132656 | biostudies-other | 1992 Jun

REPOSITORIES: biostudies-other

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Project description:Numerous host factors, in addition to human angiotensin-converting enzyme 2 (hACE2), have been identified as coreceptors of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), demonstrating broad viral tropism and diversified druggable potential. We and others have found that antihistamine drugs, particularly histamine receptor H1 (HRH1) antagonists, potently inhibit SARS-CoV-2 infection. In this study, we provided compelling evidence that HRH1 acts as an alternative receptor for SARS-CoV-2 by directly binding to the viral spike protein. HRH1 also synergistically enhanced hACE2-dependent viral entry by interacting with hACE2. Antihistamine drugs effectively prevent viral infection by competitively binding to HRH1, thereby disrupting the interaction between the spike protein and its receptor. Multiple inhibition assays revealed that antihistamine drugs broadly inhibited the infection of various SARS-CoV-2 mutants with an average IC50 of 2.4 µM. The prophylactic function of these drugs was further confirmed by authentic SARS-CoV-2 infection assays and humanized mouse challenge experiments, demonstrating the therapeutic potential of antihistamine drugs for combating coronavirus disease 19.IMPORTANCEIn addition to human angiotensin-converting enzyme 2, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can utilize alternative cofactors to facilitate viral entry. In this study, we discovered that histamine receptor H1 (HRH1) not only functions as an independent receptor for SARS-CoV-2 but also synergistically enhances ACE2-dependent viral entry by directly interacting with ACE2. Further studies have demonstrated that HRH1 facilitates the entry of SARS-CoV-2 by directly binding to the N-terminal domain of the spike protein. Conversely, antihistamine drugs, primarily HRH1 antagonists, can competitively bind to HRH1 and thereby prevent viral entry. These findings revealed that the administration of repurposable antihistamine drugs could be a therapeutic intervention to combat coronavirus disease 19.

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Histamine H1-receptor-mediated calcium influx in DDT1MF-2 cells.

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