Optimisation of Tyrosine-based lead molecules capable of Modulation of the Peroxisome Proliferator-Activated Receptor Gamma

The peroxisome proliferator-activated receptor gamma (PPARγ) agonist rosiglitazone has recently been withdrawn from the European market and its use has been restricted in the US due to its undesirable effects which were considered to outweigh its benefits. Literature indicates that there are two agonist bound conformations of the PPARγ as exemplified by its binding to rosiglitazone (PDB ID; 1FM6) and to farglitazar (PDB ID; 1FM9). This study aims to explore these two conformations, and to evaluate whether they should be targeted separately in the context of drug design studies. Furthermore, it was aimed to design a series of molecules with the potential to act as leads in a drug design process and the capability of agonist activity at the PPARγ with an acceptable side effect profile. In silico ligand binding affinities (pKd) of rosiglitazone and farglitazar within their cognate receptors were 6.62 and 9.70 respectively. The farglitazar conformer that bound optimally within the rosiglitazone bound PPARγ ligand binding pocket was identified and its binding affinity (pKd) re-determined. An analogous conformational analysis of rosiglitazone within the farglitazar bound PPARγ ligand binding pocket was carried out. The binding affinities (pKd) for these optimum conformations were 8.12 and 6.16 respectively. De novo novel structures were generated in silico based on the tyrosine-agonist farglitazar and its cognate ligand binding pocket. Moreover, analysis of the binding modality of farglitazar indicates that this molecule accesses the PPARγ ligand binding pocket more completely than does rosiglitazone. Binding affinity studies have shown that the PPARγ ligand binding pocket adopts diverse ligand driven conformations.peer-reviewe

Metabolite Cross-Feeding Enhances Virulence in a Model Polymicrobial Infection

Microbes within polymicrobial infections often display synergistic interactions resulting in enhanced pathogenesis; however, the molecular mechanisms governing these interactions are not well understood. Development of model systems that allow detailed mechanistic studies of polymicrobial synergy is a critical step towards a comprehensive understanding of these infections in vivo. In this study, we used a model polymicrobial infection including the opportunistic pathogen Aggregatibacter actinomycetemcomitans and the commensal Streptococcus gordonii to examine the importance of metabolite cross-feeding for establishing co-culture infections. Our results reveal that co-culture with S. gordonii enhances the pathogenesis of A. actinomycetemcomitans in a murine abscess model of infection. Interestingly, the ability of A. actinomycetemcomitans to utilize L-lactate as an energy source is essential for these co-culture benefits. Surprisingly, inactivation of L-lactate catabolism had no impact on mono-culture growth in vitro and in vivo suggesting that A. actinomycetemcomitans L-lactate catabolism is only critical for establishing co-culture infections. These results demonstrate that metabolite cross-feeding is critical for A. actinomycetemcomitans to persist in a polymicrobial infection with S. gordonii supporting the idea that the metabolic properties of commensal bacteria alter the course of pathogenesis in polymicrobial communities

Nicorandil-induced oral ulceration

Oral ulceration has many aetiological factors. The antianginal drug Nicorandil is becoming increasingly recognised as a causative factor for oral ulceration. The aim of this case report is to increase awareness among clinicians (medical and dental) that nicorandil can induce extensive oral ulceration and thus should be included in the differential diagnosis when presented with patients complaining of long-standing oral ulceration

Proteasome α6 subunit negatively regulates the JAK/STAT pathway and blood cell activation in Drosophila melanogaster

Abstract JAK/STAT signaling regulates central biological functions such as development, cell differentiation and immune responses. In Drosophila, misregulated JAK/STAT signaling in blood cells (hemocytes) induces their aberrant activation. Using mass spectrometry to analyze proteins associated with a negative regulator of the JAK/STAT pathway, and by performing a genome-wide RNAi screen, we identified several components of the proteasome complex as negative regulators of JAK/STAT signaling in Drosophila. A selected proteasome component, Prosα6, was studied further. In S2 cells, Prosα6 silencing decreased the amount of the known negative regulator of the pathway, ET, leading to enhanced expression of a JAK/STAT pathway reporter gene. Silencing of Prosα6 in vivo resulted in activation of the JAK/STAT pathway, leading to the formation of lamellocytes, a specific hemocyte type indicative of hemocyte activation. This hemocyte phenotype could be partially rescued by simultaneous knockdown of either the Drosophila STAT transcription factor, or MAPKK in the JNK-pathway. Our results suggest a role for the proteasome complex components in the JAK/STAT pathway in Drosophila blood cells both in vitro and in vivo