A decade of PrEP: the evolution of HIV pre-exposure prophylaxis content and sentiments in South African print news media, 2012-2021.

After nearly a decade of HIV pre-exposure prophylaxis (PrEP) rollout in sub-Saharan Africa, there has been limited study of PrEP messaging in news media. We selected twenty South African newspapers with the highest circulation volumes to retrieve articles published in 2012-2021 mentioning PrEP (N = 249). Using inductive content analysis, we developed a structured codebook to characterise PrEP-related content and sentiments, as well as their evolution over time, in the South African press. Many articles espoused favourable attitudes towards PrEP (52%), but a sizeable fraction espoused unfavourable attitudes (11%). Relative to PrEP-favourable articles, PrEP-unfavourable articles were significantly more likely to emphasise the drawbacks/consequences of PrEP use, including adherence/persistence requirements (52% vs. 24%, p = .007), cost (48% vs. 11%, p < .001), and risk compensation (52% vs. 5%, p < .001). Nevertheless, the presence of these drawbacks/consequences in print media largely declined over time. Key populations (e.g. adolescents, female sex workers) were frequently mentioned potential PrEP candidates. Despite message variations over time, prevention effectiveness and adherence/persistence requirements were the most widely cited PrEP benefits and drawbacks, respectively. Study findings demonstrate the dynamic nature of PrEP coverage in the South African press, likely in response to PrEP scale-up and real-world PrEP implementation during the study period.

Physical and functional links between anion exchanger-1 and sodium pump.

Anion exchanger-1 (AE1) mediates chloride-bicarbonate exchange across the plasma membranes of erythrocytes and, via a slightly shorter transcript, kidney epithelial cells. On an omnivorous human diet, kidney AE1 is mainly active basolaterally in α-intercalated cells of the collecting duct, where it is functionally coupled with apical proton pumps to maintain normal acid-base homeostasis. The C-terminal tail of AE1 has an important role in its polarized membrane residency. We have identified the ß1 subunit of Na(+),K(+)-ATPase (sodium pump) as a binding partner for AE1 in the human kidney. Kidney AE1 and ß1 colocalized in renal α-intercalated cells and coimmunoprecipitated (together with the catalytic α1 subunit of the sodium pump) from human kidney membrane fractions. ELISA and fluorescence titration assays confirmed that AE1 and ß1 interact directly, with a Kd value of 0.81 µM. GST-AE1 pull-down assays using human kidney membrane proteins showed that the last 11 residues of AE1 are important for ß1 binding. siRNA-induced knockdown of ß1 in cell culture resulted in a significant reduction in kidney AE1 levels at the cell membrane, whereas overexpression of kidney AE1 increased cell surface sodium pump levels. Notably, membrane staining of ß1 was reduced throughout collecting ducts of AE1-null mouse kidney, where increased fractional excretion of sodium has been reported. These data suggest a requirement of ß1 for proper kidney AE1 membrane residency, and that activities of AE1 and the sodium pump are coregulated in kidney.

Glyceraldehyde 3-phosphate dehydrogenase is required for band 3 (anion exchanger 1) membrane residency in the mammalian kidney.

The mammalian kidney isoform of the essential chloride-bicarbonate exchanger AE1 differs from its erythrocyte counterpart, being shorter at its N terminus. It has previously been reported that the glycolytic enzyme GAPDH interacts only with erythrocyte AE1, by binding to the portion not found in the kidney isoform. (Chu H, Low PS. Biochem J 400:143-151, 2006). We have identified GAPDH as a candidate binding partner for the C terminus of both AE1 and AE2. We show that full-length AE1 and GAPDH coimmunoprecipitated from both human and rat kidney as well as from Madin-Darby canine kidney (MDCK) cells stably expressing kidney AE1, while in human liver, AE2 coprecipitated with GAPDH. ELISA and glutathione S-transferase (GST) pull-down assays using GST-tagged C-terminal AE1 fusion protein confirmed that the interaction is direct; fluorescence titration revealed saturable binding kinetics with Kd 2.3±0.2 µM. Further GST precipitation assays demonstrated that the D902EY residues in the D902EYDE motif located within the C terminus of AE1 are important for GAPDH binding. In vitro GAPDH activity was unaffected by C-terminal AE1 binding, unlike in erythrocytes. Also, differently from red cell N-terminal binding, GAPDH-AE1 C-terminal binding was not disrupted by phosphorylation of AE1 in kidney AE1-expressing MDCK cells. Importantly, small interfering RNA knockdown of GAPDH in these cells resulted in significant intracellular retention of AE1, with a concomitant reduction in AE1 at the cell membrane. These results indicate differences between kidney and erythrocyte AE1/GAPDH behavior and show that in the kidney, GAPDH is required for kidney AE1 to achieve stable basolateral residency.

Apical ammonium inhibition of cAMP-stimulated secretion in T84 cells is bicarbonate dependent.

Normal human colonic luminal (NH(4)(+)) concentration ([NH(4)(+)]) ranges from approximately 10 to 100 mM. However, the nature of the effects of NH(4)(+) on transport, as well as NH(4)(+) transport itself, in colonic epithelium is poorly understood. We elucidate here the effects of apical NH(4)(+) on cAMP-stimulated Cl(-) secretion in colonic T84 cells. In HEPES-buffered solutions, 10 mM apical NH(4)(+) had no significant effect on cAMP-stimulated current. In contrast, 10 mM apical NH(4)(+) reduced current within 5 min to 61 +/- 4% in the presence of 25 mM HCO(3)(-). Current inhibition was not simply due to an increase in extracellular K(+)-like cations, in that the current magnitude was 95 +/- 5% with 10 mM apical K(+) and 46 +/- 3% with 10 mM apical NH(4)(+) relative to that with 5 mM apical K(+). We previously demonstrated that inhibition of Cl(-) secretion by basolateral NH(4)(+) occurs in HCO(3)(-)-free conditions and exhibits anomalous mole fraction behavior. In contrast, apical NH(4)(+) inhibition of current in HCO(3)(-) buffer did not show anomalous mole fraction behavior and followed the absolute [NH(4)(+)] in K(+)-NH(4)(+) mixtures, where K(+) concentration + [NH(4)(+)] = 10 mM. The apical NH(4)(+) inhibitory effect was not prevented by 100 microM methazolamide, suggesting no role for apical carbonic anhydrase. However, apical NH(4)(+) inhibition of current was prevented by 10 min of pretreatment of the apical surface with 500 microM DIDS, 100 microM 4,4'-dinitrostilbene-2,2'-disulfonic acid (DNDS), or 25 microM niflumic acid, suggesting a role for NH(4)(+) action through an apical anion exchanger. mRNA and protein for the apical anion exchangers SLC26A3 [downregulated in adenoma (DRA)] and SLC26A6 [putative anion transporter (PAT1)] were detected in T84 cells by RT-PCR and Northern and Western blots. DRA and PAT1 appear to associate with CFTR in the apical membrane. We conclude that the HCO(3)(-) dependence of apical NH(4)(+) inhibition of secretion is due to the action of NH(4)(+) on an apical anion exchanger.

Methylation at mouse Cdkn1c is acquired during postimplantation development and functions to maintain imprinted expression.

Monoallelic expression of imprinted genes is generally associated with differential methylation. Methylation may be inherited as the gametic imprinting mark or may be acquired postfertilization. Here, we characterize a differentially methylated region associated with the mouse Cdkn1c gene and find that it is confined to a CpG island that begins 600 bp 5' of the promoter and extends into the transcription unit. Our analysis indicates that methylation of this region is not inherited from sperm, is acquired specifically on the paternal allele following implantation, and is dependent on KvDMR1. We further demonstrate that although methylation is required for maintaining silencing of the paternal Cdkn1c allele, it is not a prerequisite for the establishment of monoallelic expression at this locus. Prior to the onset of differential methylation, additional epigenetic modifications must play a role in distinguishing the parental alleles of Cdkn1c and influencing their expression.