1. The effects of substrate concentration and enzyme source (human liver microsomes and recombinant cytochrome P450s, CYP) on the activation of 7-benzyloxyresorufin O-debenzylation and nifedipine oxidation were investigated. 2. 7-Benzyloxyresorufin O-debenzylase activity in human liver microsomes was inhibited by a monoclonal antibody against CYP2B6 and a polyclonal antibody against CYP3A2 by 53-69 and 19-44%, respectively, suggesting that CYP2B6 and CYP3A4 mainly catalyse 7-benzyloxyresorufin O-debenzylation in human liver microsomes. 3. 7-Benzyloxyresorufin O-debenzylase activity at 0.2-5 micro M substrate concentrations in human liver microsomes was increased by the addition of alpha-naphthoflavone, quinidine, testosterone and progesterone, and the V(max) of 7-benzyloxyresorufin O-debenzylation increased with increasing alpha-naphthoflavone concentrations, whereas the K(m) remained constant. Additionally, 7-benzyloxyresorufin O-debenzylation by recombinant CYP3A4 was increased by the addition of alpha-naphthoflavone, testosterone and progesterone but not by quinidine, whereas no chemicals tested could activate the O-debenzylation of 7-benzyloxyresorufin by CYP2B6. 4. The K(m) for nifedipine oxidation activity by CYP3A4 decreased by the addition of progesterone, whereas the V(max) remained constant. Quinidine and testosterone increased 7-benzyloxyresorufin O-debenzylase and nifedipine oxidase activities, respectively, in human liver microsomes, whereas activation was not observed in CYP3A4. 5. The results suggest that in vitro activation patterns are substrate dependent and that selection of the enzyme source can influence the activation phenomenon.
Purpose
Potential retinal adverse events after COVID-19 vaccinations reported previously include paracentral acute middle maculopathy (PAMM), acute macular neuroretinopathy (AMN), and central serous chorioretinopathy. We report four cases of branch retinal artery occlusion (BRAO), one case of PAMM, and one case of AMN that occurred after administration of the Pfizer-BioNTech COVID-19 vaccine.
Patients and Methods
We retrospectively reviewed the medical records of six patients who presented to Yame General Hospital or Oita University Hospital from July through October 2021.
Results
Four patients (2 males) presented with visual field defects associated with BRAO, one male patient with PAMM, and one female patient with AMN after receiving the Pfizer-BioNTech COVID-19 vaccine. The mean age was 59.3 years; the mean best-corrected visual acuity was 20/21. The mean time from the last vaccination to the onset of visual field defect was 22.8 days. Five patients had received two doses of the vaccine and one patient one dose. Patients’ medical history included diabetes mellitus in case 2, hypertension in cases 2, 3 and 6, and Alport syndrome and end-stage renal disease in case 6 for which the patient was undergoing regular hemodialysis.
Conclusion
Although rare, retinal adverse events may occur after COVID-19 vaccinations. Further studies with a larger sample size should determine whether these retinal abnormalities are causally associated with COVID-19 vaccinations or just coincidental. Potential risks of BRAO/PAMM/AMN after COVID-19 vaccinations must be carefully weighed against the substantial benefit of COVID-19 vaccinations.
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