Neuroprotective effects of the salidroside derivative SHPL-49 via the BDNF/TrkB/Gap43 pathway in rats with cerebral ischemia.

Ischemic stroke is a common intravascular disease and one of the leading causes of death and disability. The salidroside derivative SHPL-49, which we previously synthesized, significantly attenuates cerebral ischemic injury in a rat model of permanent middle cerebral artery occlusion. To explore the neuroprotective mechanism of SHPL-49, the effects of SHPL-49 on the expression levels of neurotrophic factors in neurons and microglia and the polarization of microglia were investigated in the present study. SHPL-49 activated the brain-derived neurotrophic factor (BDNF) pathway, decreased the number of degenerated neurons, and accelerated neurogenesis in rats with cerebral ischemia. In addition, SHPL-49 promoted the polarization of microglia toward the M2 phenotype to alleviate neuroinflammation. In BV2 cells, SHPL-49 upregulated CD206 mRNA and protein levels and inhibited CD86 mRNA and protein levels. SHPL-49 also increased neurotrophic factor secretion in BV2 cells, which indirectly promoted the survival of primary neurons after oxygen-glucose deprivation (OGD). Proteomics analysis revealed that SHPL-49 promoted growth-associated protein 43 (Gap43) expression. SHPL-49 enhanced synaptic plasticity and increased Gap43 protein levels via activation of the BDNF pathway in the OGD primary neuron model. These results indicate that SHPL-49 prevents cerebral ischemic injury by activating neurotrophic factor pathways and altering microglial polarization. Thus, SHPL-49 is a potential neuroprotective agent.

Multi-pathway neuroprotective effects of a novel salidroside derivative SHPL-49 against acute cerebral ischemic injury.

SHPL-49 ((2R,3S,4S,5R,6R)-2-(hydroxymethyl)-6-(4-(4-methoxyphenyl) butoxy) tetrahydro-2H-pyran-3,4,5-triol) is a novel glycoside derivative obtained from structural modification of salidroside, which is isolated from the medicinal plant Rhodiola rosea L. SHPL-49 was administered to rats with permanent middle cerebral artery occlusion (pMCAO) for 5 days, and it was found that SHPL-49 could alleviate the cerebral infarct volume and reduce the neurological deficit score. Moreover, the effective time window of SHPL-49 in the pMCAO model was from 0.5 to 8 h after embolization. In addition, the result of immunohistochemistry showed that SHPL-49 could increase the number of neurons in the brain tissue and reduce the occurrence of apoptosis. Morris water maze and Rota-rod experiments showed that SHPL-49 could improve neurological deficits, repair neurocognitive and motor dysfunction, and enhance learning and memory ability in the pMCAO model after 14 days of SHPL-49 treatment. Further in vitro experiments showed that SHPL-49 significantly reduced the calcium overload of PC-12 cells and the production of reactive oxygen species (ROS) induced by oxygen and glucose deprivation (OGD), and increased the levels of antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), decreased the production of malondialdehyde (MDA). Furthermore, SHPL-49 could reduce cell apoptosis by increasing protein expression ratio of anti-apoptotic factor Bcl-2 to pro-apoptotic factor Bax in vitro. SHPL-49 also regulated the expression of Bcl-2 and Bax in ischemic brain tissue, and even inhibited the caspase cascade of pro-apoptotic proteins Cleaved-caspase 9 and Cleaved-caspase 3. Taken together, SHPL-49 exhibited neuroprotective effects against cerebral ischemic injury through multiple pathways, such as alleviating calcium overload, reducing oxidative stress damage, and inhibiting apoptosis.

Bacteria-targeting liposomes for enhanced delivery of cinnamaldehyde and infection management.

PURPOSE: Drug-resistant gram-negative bacteria have emerged as a global crisis. Therefore, novel antibiotics and novel anti-infection strategies are urgently needed. Current antibiotics remain unsatisfactory due to poor targeting efficiency and poor drug penetration through the bacterial cell wall. Thus, targeted delivery of antibiotics into gram-negative bacteria should be a promising approach. Moreover, gram-negative bacteria can release lipopolysaccharide (LPS) to induce inflammatory response and septic shock, further increasing the disease burden. Hence, it is also promising to neutralize LPS while delivering antibiotics. This study aims to develop a multifunctional bacteria-targeting liposome that could enhance the delivery of antibiotics and adsorb LPS. METHODS: A polymyxin B (PMB)-modified liposomal system (P-Lipo) was developed as novel carrier of cinnamaldehyde (CA) by using a thin-film evaporation method. Liposome morphology, size, zeta potential, stability, entrapment efficiency, and in vitro release were systematically evaluated. The bacteria-targeting effect and LPS-neutralizing capacity of P-Lipo were evaluated both in vitro and in vivo. The antibacterial effect of CA-loaded P-Lipo was assessed in Escherichia coli (E. coli) O157:H7 and Pseudomonas aeruginosa (P. aeruginosa). Ultimately, the therapeutic effect of P-CA-Lipo was investigated in E. coli O157:H7-infected mice. RESULTS: P-Lipo was successfully synthesized and encapsulated with CA, which was well characterized. Both in vivo and in vitro experiments demonstrated that P-Lipo could efficiently target the E. coli after modification with PMB. Compared with free CA, CA-Lipo, and P-Lipo, P-CA-Lipo exhibited a significantly enhanced inhibitory effect on E. coli and P. aeruginosa. Further analysis demonstrated that P-CA-Lipo improved the bacterial uptake of CA and enhanced its antibacterial effect. It was also confirmed that P-Lipo could neutralize the LPS to avoid the inflammatory responses and inhibit the release of proinflammatory cytokines in both macrophages and mice. Finally, P-CA-Lipo inhibited E. coli-induced skin damage and death in mice and showed good biocompatibility. CONCLUSION: The P-Lipo could target E. coli by binding with LPS and enhancing the delivery and internalization of CA. In addition, P-Lipo could adsorb free LPS synergistically, thus promoting the infection management. We believe that this strategy can provide innovative insights into antibacterial agent delivery for the treatment of persistent and severe bacterial infections.

Bacteria-Anchoring Hybrid Liposome Capable of Absorbing Multiple Toxins for Antivirulence Therapy of Escherichia coli Infection.

Antivirulence therapy by cell membrane coated nanoparticles has shown promise against bacterial infections. However, current approaches remain unsatisfactory when facing Escherichia coli (E. coli) infections, since the E. coli secretes multiple bacterial toxins including endotoxins and exotoxins that are challenging to eliminate simultaneously. What is worse, the absorptive scavengers normally rely on random contact of the diffuse toxins, which is not efficient. For the current cell membrane coated platform, the single type of cell membrane cannot fully meet the detoxing requirement facing multiple toxins. To address these problems, a polymyxin B (PMB)-modified, red blood cell (RBC)-mimetic hybrid liposome (P-RL) was developed. The P-RL was fabricated succinctly through fusion of PMB-modified lipids and the RBC membranes. By the strong interaction between PMB and the E. coli membrane, P-RL could attach and anchor to the E. coli; attributed to the fused RBC membrane and modified PMB, the P-RL could then efficiently neutralize both endotoxins and exotoxins from the toxin fountainhead. In vitro and in vivo results demonstrated the P-RL had a significant anchoring effect to E. coli. Moreover, compared with the existing RBC vesicles or PMB-modified liposomes, P-RL exhibited a superior therapeutic effect against RBC hemolysis, macrophage activation, and a mixed-toxin infection in mice. Potently, P-RL could inhibit E. coli O157:H7-induced skin damage, intestinal infection, and mouse death. Overall, the P-RL could potentially improve the detoxing efficiency and markedly expand the detoxification spectrum of current antivirulence systems, which provides different insights into drug-resistant E. coli treatment.