Molecular simplification of lipid A structure: TLR4-modulating cationic and anionic amphiphiles

A growing body of data suggests that therapies based on Toll-like receptors (TLR) targeting, in particular TLR4, holds promise in curing autoimmune and inflammatory pathologies still lacking specific treatment, included several rare diseases. While TLR4 activators (agonists) have already found successful clinical application as vaccine adjuvants, the use of TLR4 blockers (antagonists) as antisepsis agents or as agents against inflammatory diseases (including arthritis, multiple sclerosis, neuroinflammations) and cancer is still at a preclinical phase of development. This minireview focuses on recent achievements on the development of TLR4 modulators based on lipid A structure simplification, in particular on compounds having disaccharide or monosaccharide structures. As the TLR4 activity of natural TLR4 ligands (lipopolysaccharide, LPS and its biologically active part, the lipid A) depends on both the structure of endotoxin aggregates in solution and on single-molecule interaction with MD-2 and CD14 receptors, the rational design of TLR4 modulators should in principle take into account both these factors. In the light of the most recent advances in the field, in this minireview we discuss the structure–activity relationship in simplified lipid A analogs, with cationic or anionic amphiphilic structures.     

The Well-being Model: A New Drug Interaction Model for Positive and Negative Effects

Background: Drugs are routinely combined in anesthesia and pain management to obtain an enhancement of the desired effects. However, a parallel enhancement of the undesired effects might take place as well, resulting in a limited therapeutic usefulness. Therefore, when addressing the question of optimal drug combinations, side effects must be taken into account.

Methods: By extension of a previously published interaction model, the authors propose a method to study drug interactions considering also their side effects. A general outcome parameter identified as patient's well-being is defined by superposition of positive and negative effects. Well-being response surfaces are computed and analyzed for varying drugs pharmacodynamics and interaction types. In particular, the existence of multiple maxima and of optimal drug combinations is investigated for the combination of two drugs.

Results: Both drug pharmacodynamics and interaction type affect the well-being surface and the deriving optimal combinations. The effect of the interaction parameters can be explained in terms of synergy and antagonism and remains unchanged for varying pharmacodynamics. For all simulations performed for the combination of two drugs, the presence of more than one maximum was never observed.     

Norepinephrine modulates glutamatergic transmission in the bed nucleus of the stria terminalis.

The bed nucleus of the stria terminalis (BNST) and its adrenergic input are key components in stress-induced reinstatement and maintenance of drug use. Intra-BNST injections of either beta-adrenergic receptor (beta-AR) antagonists or alpha2-adrenergic receptor (alpha2-AR) agonists can inhibit footshock-induced reinstatement and maintenance of cocaine- and morphine-seeking. Using electrophysiological recording methods in an in vitro slice preparation from C57/Bl6j adult male mouse BNST, we have examined the effects of adrenergic receptor activation on excitatory synaptic transmission in the lateral dorsal supracommissural BNST (dBNST) and subcommissural BNST (vBNST). Alpha2-AR activation via UK-14,304 (10 microM) results in a decrease in excitatory transmission in both dBNST and vBNST, an effect predominantly dependent upon the alpha2A-AR subtype. Beta-AR activation via isoproterenol (1 microM) results in an increase in excitatory transmission in dBNST, but not in vBNST. Consistent with the work with receptor subtype specific agonists, application of the endogenous ligand norepinephrine (NE, 100 microM) elicits two distinct effects on glutamatergic transmission. In dBNST, NE elicits an increase in transmission (62% of dBNST NE experiments) or a decrease in transmission (38% of dBNST NE experiments). In vBNST, NE elicits a decrease in transmission in 100% of the experiments. In dBNST, the NE-induced increase in synaptic transmission is blocked by beta1/beta2- and beta2-, but not beta1-specific antagonists. In addition, this increase is also reduced by the alpha2-AR antagonist yohimbine and is absent in the alpha2A-AR knockout mouse. In vBNST, the NE-induced decrease in synaptic transmission is markedly reduced in the alpha2A-AR knockout mouse. Further experiments demonstrate that the actions of NE on glutamatergic transmission can be correlated with beta-AR function.     

Electrochemical study of endodontic silver cones used in root canal therapy

In previous studies it was observed that endodontic silver cones placed in fine canals became dislodged as a result of corrosion. To investigate the corrosion of high purity silver, potentiostatic and potentiodynamic electrochemical techniques were used. Triangular potential sweeps made in physiological solutions and human plasma showed similar potential-current relationships. However, in human plasma, peak currents were lower and peak potentials were more anodic than those observed in the physiological solutions. The electron microprobe analysis and the EDAX of the film formed in the biological fluids revealed the presence of silver and chloride and a certain amount of carbon. The addition of small quantities of Na2S to the physiological solutions favoured metal dissolution and promoted the formation of a mixed film of AgCL and Ag2S. According to these results chloride and sulphide anions seem to be particularly aggressive towards the metal surface in implanted silver cones. Precautions to avoid direct contact of the cones with saliva and tissue fluids must be taken. Fractures and discontinuities present in the cement considerably increase the corrosion risks.     

The aging process and potential interventions to extend life expectancy

Aging is commonly defined as the accumulation of diverse deleterious changes occurring in cells and tissues with advancing age that are responsible for the increased risk of disease and death. The major theories of aging are all specific of a particular cause of aging, providing useful and important insights for the understanding of age-related physiological changes. However, a global view of them is needed when debating of a process which is still obscure in some of its aspects. In this context, the search for a single cause of aging has recently been replaced by the view of aging as an extremely complex, multifactorial process. Therefore, the different theories of aging should not be considered as mutually exclusive, but complementary of others in the explanation of some or all the features of the normal aging process. To date, no convincing evidence showing the administration of existing “anti-aging” remedies can slow aging or increase longevity in humans is available. Nevertheless, several studies on animal models have shown that aging rates and life expectancy can be modified. The present review provides an overlook of the most commonly accepted theories of aging, providing current evidence of those interventions aimed at modifying the aging process.