Cysteamine inhibits lysosomal oxidation of low density lipoprotein in human macrophages and reduces atherosclerosis in mice

Background and aims: We have shown previously that low density lipoprotein (LDL) aggregated by vortexing is internalised by macrophages and oxidised by iron in lysosomes to form the advanced lipid/protein oxidation product ceroid. We have now used sphingomyelinase-aggregated LDL, a more pathophysiological form of aggregated LDL, to study lysosomal oxidation of LDL and its inhibition by antioxidants, including cysteamine (2-aminoethanethiol) which concentrates in lysosomes by several orders of magnitude. We have also investigated the effect of cysteamine on atherosclerosis in mice. Methods: LDL was incubated with sphingomyelinase, which increased its average particle diameter from 26 to 170 nm, and was then incubated for up to 7 days with human monocyte-derived macrophages. LDL receptor-deficient mice were fed a Western diet (19-22 per group) and some given cysteamine in their drinking water at a dose equivalent to that used in cystinosis patients. The extent of atherosclerosis in the aortic root and the rest of the aorta was measured. Results: Confocal microscopy revealed lipid accumulation in lysosomes in the cultured macrophages. Large amounts of ceroid were produced, which colocalised with the lysosomal marker LAMP2. The antioxidants cysteamine, butylated hydroxytoluene, amifostine and its active metabolite WR-1065, inhibited the production of ceroid. Cysteamine at concentrations well below those expected to be present in lysosomes inhibited the oxidation of LDL by iron ions at lysosomal pH (pH 4.5) for prolonged periods. Finally, we showed that the extent of atherosclerotic lesions in the aortic root and arch of mice was significantly reduced by cysteamine. Conclusions: These results support our hypothesis that lysosomal oxidation of LDL is important in atherosclerosis and hence antioxidant drugs that concentrate in lysosomes might provide a novel therapy for this disease

Pre-existing Igg antibodies to Hcovs Nl63 and Oc43 spike increased during the pandemic and after Covid-19 vaccination

Pre-existing immunity is associated with increased protection against SARS-CoV-2. There is little information regarding endemic human coronaviruses (HCOVs) from Pakistan. We investigated antibodies to SARS-CoV-2 and HCOVs NL63 and OC43, before and during the pandemic and determined the effect of COVID-19 vaccinations. We measured IgG to Spike proteins of SARS-CoV-2 in sera from pre-pandemic and post-pandemic periods (HC 2021). A psuedotyped virus assay was used to investigate serum neutralizing activity. We also measured IgG to SARS-CoV-2, HCoV-NL63 and HCoV-OC43 after individuals received either inactivated (Sinovac), or mRNA (BNT162b2), following up to weeks. Pre-pandemic sera showed low levels of IgG antibodies to Spike SARS-CoV-2 as well as low neutralizing capacity. Anti-SARS-CoV-2 Spike increased in HC 2021 to 49% seropositivity with equivalent neutralization capacity. Antibodies to IgG to HCoV-NL63 and HCoV-OC43 were higher in pandemic as compared with pandemic sera. IgG to Spike SARS-CoV-2 were positively correlated with HCoV-NL63 Spike only in pandemic sera, prior to vaccinations. Furthermore, SinoVac and BNT162b2 vaccinations both resulted in an increase in IgG antibodies to Spike SARS-CoV-2, HCoV-NL63 and HCoV-OC43. Pre-existing antibodies to endemic coronaviruses likely enhanced immunity in the population by driving cross reactive IgG antibodies, thereby enhancing protection against COVID-19