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Synthesis of Biscoumarin and Dihydropyran Derivatives and Evaluation of Their Antibacterial Activity

In an attempt to find a new class antibacterial agents, a series of biscoumarins (1–4) and dihydropyrans (5–13) were successfully prepared. The molecular structures of four representative compounds, that is, 4, 5, 8 and 12 were confirmed by single crystal X-ray diffraction study. These synthesized compounds were screened for their antibacterial activity in vitro against Staphylococcus aureus (S. aureus ATCC 29213), methicillin-resistant S. aureus (MRSA XJ 75302), vancomycin-intermediate S. aureus (Mu50 ATCC 700699), USA 300 (Los Angeles County clone, LAC), Staphylococcus epidermidis (S. epidermidis ATCC 14990), methicillin-resistant S. epidermidis (MRSE XJ 75284) and Escherichia coli (E. coli ATCC 25922). Additionally, there are two classical intramolecular O–H···O hydrogen bonds (HBs) in biscoumarins 1–4 and the corresponding HB energies were further performed with the density functional theory (DFT) [B3LYP/6-31G*] method.

New biscoumarin and dihydropyran derivatives as antimicrobials

In an attempt to find a new class of antimicrobial agents, a series of biscoumarin (1–4) and dihydropyran (5 and 6) derivatives were prepared. These compounds were screened for their in vitro antibacterial activity against Staphylococcus aureus (S. aureus ATCC 29213), methicillin-resistant S. aureus (MRSA XJ 75302), vancomycin-intermediate S. aureus (Mu50 ATCC 700699), and USA 300 (Los Angeles County clone, LAC). There are two classical intramolecular O–H···O hydrogen bonds (HBs) in the structures of biscoumarins 1–4 and the corresponding total HB energy were further performed with the density functional theory (DFT) [B3LYP/6-31G*] method.

An Orally Active Allosteric GLP-1 Receptor Agonist Is Neuroprotective in Cellular and Rodent Models of Stroke.

Diabetes is a major risk factor for the development of stroke. Glucagon-like peptide-1 receptor (GLP-1R) agonists have been in clinical use for the treatment of diabetes and also been reported to be neuroprotective in ischemic stroke. The quinoxaline 6,7-dichloro-2-methylsulfonyl-3-N-tert- butylaminoquinoxaline (DMB) is an agonist and allosteric modulator of the GLP-1R with the potential to increase the affinity of GLP-1 for its receptor. The aim of this study was to evaluate the neuroprotective effects of DMB on transient focal cerebral ischemia. In cultured cortical neurons, DMB activated the GLP-1R, leading to increased intracellular cAMP levels with an EC50 value about 100 fold that of exendin-4. Pretreatment of neurons with DMB protected against necrotic and apoptotic cell death was induced by oxygen-glucose deprivation (OGD). The neuroprotective effects of DMB were blocked by GLP-1R knockdown with shRNA but not by GLP-1R antagonism. In C57BL/6 mice, DMB was orally administered 30 min prior to middle cerebral artery occlusion (MCAO) surgery. DMB markedly reduced the cerebral infarct size and neurological deficits caused by MCAO and reperfusion. The neuroprotective effects were mediated by activation of the GLP-1R through the cAMP-PKA-CREB signaling pathway. DMB exhibited anti-apoptotic effects by modulating Bcl-2 family members. These results provide evidence that DMB, a small molecular GLP-1R agonist, attenuates transient focal cerebral ischemia injury and inhibits neuronal apoptosis induced by MCAO. Taken together, these data suggest that DMB is a potential neuroprotective agent against cerebral ischemia.

Pro-GLP-1, a Pro-drug of GLP-1, is neuroprotective in cerebral ischemia

Pro-Glucagon-like peptide-1 (Pro-GLP-1), a long-lasting GLP-1 receptor (GLP-1R) agonist, was developed using a polymeric pro-drug strategy and its neuroprotective effects on ischemic stroke were investigated in C57BL/6 mice. Pro-GLP-1 was injected into the intraperitoneal cavity of C57BL/6 mice once a day for 7days before middle cerebral artery occlusion (MCAO) surgery. The neurological deficit score and TTC staining were determined 24h after ischemia. The results demonstrated that Pro-GLP-1 was slowly degraded in the plasma and brain of the mice, and GLP-1 could be detected even 12h after administration. Pro-GLP-1 was significantly neuroprotective in C57BL/6 mice subjected to MCAO. In cultured cortical neurons, treatment with Pro-GLP-1 attenuated apoptosis induced by oxygen-glucose deprivation (OGD). The neuroprotective effects of Pro-GLP-1 were blocked by a selective GLP-1 receptor antagonist and knockdown of GLP-1 receptor with shRNA. However, Pro-GLP-1 had no effect on blood glucose and insulin levels which indicated that neuroprotection was mediated by the activation of GLP-1 receptor in the brain. Pro-GLP-1 repaired the balance of pro- and anti-apoptotic proteins and decreased the expression of caspase-3. The anti-apoptotic effect was mediated by the cAMP/PKA and PI3K/Akt pathway. Our research provides evidence that pre-treatment of MCAO mice with Pro-GLP-1 exerts a neuroprotective effect mediated by a blockade of apoptosis and that Pro-GLP-1 might be a potential neuroprotective agent candidate against ischemic stroke.

Intranasal Delivery of Exendin-4 Confers Neuroprotective Effect Against Cerebral Ischemia in Mice

Exendin-4 is now considered as a promising drug for the treatment of cerebral ischemia. To determine the neuroprotective effects of intranasal exendin-4, C57BL/6J mice were intranasally administered with exendin-4 daily for 7xa0days before middle cerebral artery occlusion (MCAO) surgery. Intranasally administered exendin-4 produced higher brain concentrations and lower plasma concentrations when compared to identical doses administered interperitoneally. Neurological deficits and volume of infarcted lesions were analyzed 24xa0h after ischemia. Intranasal administration of exendin-4 exhibited significant neuroprotection in C57BL/6 mice subjected to MCAO by reducing neurological deficit scores and infarct volume. The neuroprotective effects of exendin-4 were blocked by the knockdown of GLP-1R with shRNA. However, exendin-4 has no impact on glucose and insulin levels which indicated that the neuroprotective effect was mediated by the activation of GLP-1R in the brain. Exendin-4 intranasal administration restored the balance between pro- and anti-apoptotic proteins and decreased the expression of Caspase-3. The anti-apoptotic effect was mediated by the cAMP/PKA and PI3K/Akt pathway. These findings provided evidence that exendin-4 intranasal administration exerted a neuroprotective effect mediated by an anti-apoptotic mechanism in MCAO mice and protected neurons against ischemic injury through the GLP-1R pathway in the brain. Intranasal delivery of exendin-4 might be a promising strategy for the treatment of ischemic stroke.

Oligomerization of RNAIII-Inhibiting Peptide Inhibits Adherence and Biofilm Formation of Methicillin-Resistant Staphylococcus aureus In Vitro and In Vivo

Biofilm formation enhances bacterial resistance and complicates treatment. Therefore, an innovative strategy is urgently needed for the treatment of Staphylococcus aureus biofilm infectious diseases. RNAIII-inhibiting peptide (RIP), as a quorum-sensing inhibitor, inhibits S. aureus biofilm formation. However, RIP possesses poor antibiofilm activity when used alone or at a low dose in vivo. The activity and stability of RIP can be enhanced by designing its derivatives through amino acid substitution, terminal modification, or oligomerization. Among the derivatives, 16P-AC significantly decreased the biofilm formation and adherence of methicillin-resistant S. aureus (MRSA) on polystyrene material by inhibiting the expression level of four biofilm formation-related genes in vitro. Moreover, 16P-AC showed excellent protective effects by decreasing the bacterial titers in the urine, kidney, stent, and bladder, as well as by inhibiting intercellular adhesion on the implanted stent, in a rat urinary tract infection model induced by MRSA. This derivative also exhibited a relatively good stability in rat plasma. Therefore, 16P-AC is a potential drug candidate to treat biofilm-associated infections caused by MRSA. The present modification strategy is feasible to improve the metabolic stability and activity of RIP in vivo.

New Biscoumarin Derivatives: Synthesis, Crystal Structure, Theoretical Study and Antibacterial Activity against Staphylococcus aureus

Five novel biscoumarins 1–5 were synthesized and characterized. In these compounds, two classical asymmetrical intramolecular O–H···O hydrogen bonds were used to stabilize the whole structures and the HB energies were performed with the density functional theory (DFT) [B3LYP/6-31G*] method. The five compounds were evaluated for their in vitro antibacterial activities against Staphylococcus aureus (S. aureus ATCC 29213), methicillin-resistant S. aureus (MRSA XJ 75302), vancomycin-intermediate S. aureus (Mu50 ATCC 700699), and USA 300 (Los Angeles County clone, LAC) by the means of minimum inhibitory concentration and time-kill curves.

Evaluation of Antibacterial Activities of 4-Hydroxycoumarin Derivatives

Abstract Three kinds of 4-hydroxycoumarin derivatives, namely, biscoumarins (1–4), epoxydicoumarins (5–8) and dihydropyrans (9–12), were synthesized and the antibacterial activity of each of them was evaluated. The result of preliminary bioassay shows that the lowest minimal inhibitory concentration (MIC) of compounds 1 and 2 against drug-sensitive S. aureus (ATCC 29213) and methicillin-resistant S. aureus (MRSA XJ 75302, Mu50, ATCC 700699 and USA 300) is 4–64u202fug/mL. Additionally, there are two classical intramolecular O—H⋯O hydrogen bonds (HBs) in the structures of biscoumarins (1–4), and their corresponding HB energies were further calculated by the density functional theory (DFT) [B3LYP/6-31G*] method.

Pyroptosis of Salmonella Typhimurium -infected macrophages was suppressed and elimination of intracellular bacteria from macrophages was promoted by blocking QseC

QseC is a membrane-bound histidine sensor kinase found in Gram-negative pathogens and is involved in the regulation of bacterial virulence. LED209, a QseC-specific inhibitor, significantly inhibits the virulence of several pathogens and partially protects infected mice from death by blocking QseC. However, the mechanism of its antibacterial effects remains unclear. In this experiment, a Salmonella Typhimurium (S. Typhimurium) and macrophage co-culture system was utilized to investigate possible mechanisms underlying the antimicrobial effects of the QseC inhibitor. QseC blockade inhibited the expression of QseC-dependent virulence genes, including flhDC, sifA, and sopB, in S. Typhimurium, leading to inhibition of swimming motility, invasion capacity, and replication capacity of the pathogens. Release of lactate dehydrogenase (LDH) from S. Typhimurium-infected macrophages was significantly inhibited by blocking QseC. Activated caspase-1 and IL-1β levels were suppressed, and intracellular bacterial count was reduced in infected macrophages. QseC blockade effectively reduced the virulence of S. Typhimurium, inhibited S. Typhimurium-induced pyroptosis of macrophages, and promoted elimination of intracellular bacteria from infected macrophages. Thus, the antibacterial effects of QseC inhibitor are mediated via enhancement of intracellular killing of S. Typhimurium in macrophages.