Biochemical changes induced by strontium ranelate in differentiating adipocytes

Low bone formation in osteoporosis is associated with a shift from osteoblastic to adipogenic differentiation of mesenchymal stem cells (MSC) inducing a concomitant lipotoxic milieu within the bone marrow. Strontium ranelate (SrRN), a treatment for osteoporosis, has both anti-resorptive and anabolic effects on bone. The anabolic effect of SrRN has been associated with its effect on both osteoblastogenesis and adipogenesis. However, the effect of SrRN on the potentially lipotoxic factors produced by differentiating marrow adipocytes remains poorly understood. To expand the knowledge on the effect of SrRN treatment on the bone microenvironment, we assessed changes in adipogenic factors and adipokine expression in adipocytic differentiation of MSC in vitro. Primary human MSC were induced to differentiate in adipogenic conditions in the presence or absence of SrRN (1–2 mM). We tested the dose-dependent effects of SrRN on adipocyte differentiation including changes in the expression of adipogenic markers and adipokines. We report that adipogenesis was negatively affected in the presence of SrRN with a concomitant dose-dependent decrease in the expression of adipogenic markers and changes in adipokine profile. Taken together, our data suggests that SrRN induces biochemical changes in differentiating adipocytes that could generate a favorable osteogenic effect within the bone marrow milieu.     

Short-term antibody response after 1 dose of BNT162b2 vaccine in patients receiving hemodialysis

BACKGROUND:Patients receiving in-centre hemodialysis are at high risk of exposure to SARS-CoV-2 and death if infected. One dose of the BNT162b2 SARS-CoV-2 vaccine is efficacious in the general population, but responses in patients receiving hemodialysis are uncertain.METHODS:We obtained serial plasma from patients receiving hemodialysis and health care worker controls before and after vaccination with 1 dose of the BNT162b2 mRNA vaccine, as well as convalescent plasma from patients receiving hemodialysis who survived COVID-19. We measured anti–receptor binding domain (RBD) immunoglobulin G (IgG) levels and stratified groups by evidence of previous SARS-CoV-2 infection.RESULTS:Our study included 154 patients receiving hemodialysis (135 without and 19 with previous SARS-CoV-2 infection), 40 controls (20 without and 20 with previous SARS-CoV-2 infection) and convalescent plasma from 16 patients. Among those without previous SARS-CoV-2 infection, anti-RBD IgG was undetectable at 4 weeks in 75 of 131 (57%, 95% confidence interval [CI] 47% to 65%) patients receiving hemodialysis, compared with 1 of 20 (5%, 95% CI 1% to 23%) controls (p < 0.001). No patient with nondetectable levels at 4 weeks developed anti-RBD IgG by 8 weeks. Results were similar in non-immunosuppressed and younger individuals. Three patients receiving hemodialysis developed severe COVID-19 after vaccination. Among those with previous SARS-CoV-2 infection, median anti-RBD IgG levels at 8 weeks in patients receiving hemodialysis were similar to controls at 3 weeks (p = 0.3) and to convalescent plasma (p = 0.8).INTERPRETATION:A single dose of BNT162b2 vaccine failed to elicit a humoral immune response in most patients receiving hemodialysis without previous SARS-CoV-2 infection, even after prolonged observation. In those with previous SARS-CoV-2 infection, the antibody response was delayed. We advise that patients receiving hemodialysis be prioritized for a second BNT162b2 dose at the recommended 3-week interval.

Patients with end-stage kidney disease receiving incentre hemodialysis have been uniquely vulnerable during the COVID-19 pandemic. For these patients, unlike for most other people, self-isolation to avoid exposure to SARS-CoV-2 is impossible. Most patients receiving hemodialysis must leave their homes 3 times weekly to receive their life-saving treatments, often in shared spaces for hours at a time. COVID-19 case fatality rates are 20%–30% for patients receiving hemodialysis —10 times higher than in the general population.^1,2 Advanced age, multiple comorbidities and blunted immune response likely all contribute to the high COVID-19 death rates in this population. Some hemodialysis centres have thus prioritized these patients for vaccination.To facilitate wider vaccine distribution during current shortages, ³ the National Advisory Committee on Immunization of Canada has recommended delaying the second dose of the BNT162b2 vaccine from 3 to 16 weeks.⁴ In a randomized controlled trial (RCT), the clinical efficacy of the BNT162b2 was reported to be greater than 80% at 3 weeks after the first dose.⁵ However, no patients receiving hemodialysis were enrolled in this trial.⁵ Patients with end-stage kidney disease receiving hemodialysis often have impairments in both humoral and cellular immune responses⁶ and are noted to have lower antibody responses to other vaccines.⁷ Whether patients receiving hemodialysis develop robust immune responses after vaccination against SARS-CoV-2 remains uncertain.⁸ Data are required to better inform Canadian public health policy on whether second doses of vaccine can be safely delayed in this population.Usually, once clinical trials are completed, antibody levels can be used as surrogate measures of vaccine efficacy, such as with hepatitis B⁹ and influenza.¹⁰ With respect to the novel coronavirus SARS-CoV-2, although there is increasing understanding of the antibodies that best correlate with viral neutralization and T-cell responses,^11,12 assays vary from laboratory to laboratory and as yet there are no internationally accepted standards defining what antibody levels constitute immunity.¹³ The only way to evaluate vaccine efficacy using antibody levels, therefore, is through direct experimental comparison with controls who are known to reliably develop immunity after vaccination (i.e., healthy individuals similar to those enrolled in the RCT showing vaccine efficacy⁵) or who have developed immunity after natural infection (i.e., survivors of COVID-19).We sought to determine whether short-term antibody responses after a single dose of the BNT162b2 mRNA vaccine are comparable between patients receiving hemodialysis and healthy individuals, and how this compares with antibody responses in patients receiving hemodialysis who survived natural infection with SARS-CoV-2.     

The influence of positional isomerism on G-quadruplex binding and anti-proliferative activity of tetra-substituted naphthalene diimide compounds

The synthesis together with biophysical and biological evaluation of a series of tetra-substituted naphthalene diimide (ND) compounds, are presented. These compounds are positional isomers of a recently-described series of quadruplex-binding ND derivatives, in which the two N-methyl-piperidine-alkyl side-chains have now been interchanged with the positions of side-chains bearing a range of end-groups. Molecular dynamics simulations of a pair of positional isomers are in accord with the quadruplex stabilization and biological data for these compounds. Analysis of structure–activity data indicates that for compounds where the side-chains are not of equivalent length then the positional isomers described here tend to have improved cell proliferation potency and in some instances, superior quadruplex stabilization ability.     

Optimization of anti-proliferative activity using a screening approach with a series of bis-heterocyclic G-quadruplex ligands

Using a phenotypic screening and SAR optimization approach, a phenyl-bis-oxazole derivative has been identified with anti-proliferative activity, optimized with the use of a panel of cancer cell lines. The lead compound was synthesized by means of a short and effective two-step synthesis using Pd-catalyzed direct arylation. The compound stabilizes several quadruplex DNA sequences including a human telomeric DNA and one from the promoter of the HSP90 gene, although the structure–activity relationships of the series are not obviously related to the quadruplex binding.