Structures and Efflux Mechanisms of the AcrAB-TolC Pump.

The global emergence of multidrug resistance (MDR) in gram-negative bacteria has become a matter of worldwide concern. MDR in these pathogens is closely linked to the overexpression of certain efflux pumps, particularly the resistance-nodulation-cell division (RND) efflux pumps. Inhibition of these pumps presents an attractive and promising strategy to combat antibiotic resistance, as the efflux pump inhibitors can effectively restore the potency of existing antibiotics. AcrAB-TolC is one well-studied RND efflux pump, which transports a variety of substrates, therefore providing resistance to a broad spectrum of antibiotics. To develop effective pump inhibitors, a comprehensive understanding of the structural aspect of the AcrAB-TolC efflux pump is imperative. Previous studies on this pump's structure have been limited to individual components or in vitro determination of fully assembled pumps. Recent advancements in cellular cryo-electron tomography (cryo-ET) have provided novel insights into this pump's assembly and functional mechanism within its native cell membrane environment. Here, we present a summary of the structural data regarding the AcrAB-TolC efflux pump, shedding light on its assembly pathway and operational mechanism.

Investigation of the application of Enhanced Recovery After Surgery (ERAS) in elderly patients undergoing surgery for kidney stones.

OBJECTIVE: To investigate the efficacy and application of Enhanced Recovery After Surgery (ERAS) in elderly patients undergoing surgery for kidney stones. METHODS: Clinical data of 104 elderly patients who underwent kidney stone surgery at West China Hospital, Sichuan University from January 2020 to December 2022 were retrospectively analyzed in this study. The patients were divided into two groups according to different nursing plans. Among them, 52 patients in the control group received conventional nursing, and 52 patients in the study group received ERAS mode nursing. Postoperative recovery, anxiety, complications, stress response and quality of life were compared between the two groups. RESULTS: The time to recovery of postoperative rehabilitation indices in the research group was significantly shorter compared to the control group (P < 0.05). The research group also exhibited a significantly lower incidence of complications such as hematuria, abdominal pain, vomiting, chills, fever, and hypotension (all P < 0.05). Before the initiation of nursing care, there were no significant differences in the State Anxiety Inventory (SAI) and Trait Anxiety Inventory (TAI) scores between the two groups (both P > 0.05). However, after nursing care, the research group exhibited lower SAI and TAI scores compared to the control group (all P < 0.05). Similarly, there was no significant difference in the General Quality of Life Inventory-74 (GQOLI-74) scores in any dimension between the two groups before nursing care (P > 0.05), but the research group showcased higher scores in every dimension after nursing care (P < 0.05). The levels of Heme Oxygenase-1 (HO-1), Endothelin-1 (ET-1), Adrenocorticotropic Hormone (ACTH), and Cortisol (Cor) were significantly lower in the research group after nursing care (all P < 0.05). The acknowledgment and approval scores of nursing care in the research group were higher than those in the control group (P < 0.05). CONCLUSION: The application of ERAS in elderly patients with kidney stones undergoing transurethral ureteral holmium laser lithotripsy is efficacious in mitigating stress reactions, enhancing quality of life and reducing perioperative anxiety, minimizing the incidence of complications, and promoting overall patient recovery.

AMPA receptor inhibition alleviates inflammatory response and myocardial apoptosis after myocardial infarction by inhibiting TLR4/NF-κB signaling pathway.

Myocardial infarction leads to myocardial inflammation and apoptosis, which are crucial factors leading to heart failure and cardiovascular dysfunction, eventually resulting in death. While the inhibition of AMPA receptors mitigates inflammation and tissue apoptosis, the effectiveness of this inhibition in the pathophysiological processes of myocardial infarction remains unclear. This study investigated the role of AMPA receptor inhibition in myocardial infarction and elucidated the underlying mechanisms. This study established a myocardial infarction model by ligating the left anterior descending branch of the coronary artery in Sprague-Dawley rats. The findings suggested that injecting the AMPA receptor antagonist NBQX into myocardial infarction rats effectively alleviated cardiac inflammation, myocardial necrosis, and apoptosis and improved their cardiac contractile function. Conversely, injecting the AMPA receptor agonist CX546 into infarcted rats exacerbated the symptoms and tissue damage, as reflected by histopathology. This agonist also stimulated the TLR4/NF-κB pathway, further deteriorating cardiac function. Furthermore, the investigations revealed that AMPA receptor inhibition hindered the nuclear translocation of P65, blocking its downstream signaling pathway and attenuating tissue inflammation. In summary, this study affirmed the potential of AMPA receptor inhibition in countering inflammation and tissue apoptosis after myocardial infarction, making it a promising therapeutic target for mitigating myocardial infarction.

Efficacy of nonpharmacological interventions targeting social function in children and adults with autism spectrum disorder: A systematic review and meta-analysis.

BACKGROUND AND AIMS: This paper aimed to evaluate the use of nonpharmacological interventions for the management of autism spectrum disorder (ASD). The effects of acupuncture and behavioural therapy, two nonpharmalogical interventions, on social function in ASD patients are still controversial. This meta-analysis investigated the impact of these two treatments and compared their effects. METHODS: Seven electronic databases were systematically searched to identify randomized controlled trials (RCTs) on the use of acupuncture or behavioural therapy for ASD. A meta-analysis was carried out using Review Manager 5.4 software. Continuous data are reported as mean differences (MDs) or standardized mean differences (SMDs) with 95% confidence intervals (CIs). An assessment of methodological quality using the Cochrane risk-of-bias (ROB) tool for trials was carried out. The Grading of Recommendation Assessment, Development, and Evaluation (GRADE) was applied to evaluate the quality (certainty) of evidence for results regarding social function indicators. RESULTS: Thirty RCTs on acupuncture and 36 on behavioural therapy were included. Compared with the control condition, body acupuncture (SMD: 0.76, 95% CI: [0.52, 1.01]; low certainty), modern acupuncture technology (SMD: 0.84, 95% CI: [0.32, 1.35]; low certainty), cognitive behavioural therapy (SMD: 0.42, 95% CI: [0.26, 0.58]; high certainty), the Denver model (SMD: 0.61, 95% CI: [0.23, 0.99]; moderate certainty) and social skills training (SMD: 0.56, 95% CI: [0.41, 0.71]; moderate certainty) improved social functioning. CONCLUSION: Behavioural therapies (such as CBT, the Denver model, social skills training), improved the social functioning of patients with ASD in the short and long term, as supported by high- and moderate-quality evidence. Acupuncture (including scalp acupuncture, body acupuncture and use of modern acupuncture technology) also improved social functioning, as supported by low- and very low-quality evidence. More high-quality evidence is needed to confirm the effect of acupoint catgut embedding and Early Intensive Behavioural Intervention (EIBI).

Membrane translocation process revealed by in situ structures of type II secretion system secretins.

The GspD secretin is the outer membrane channel of the bacterial type II secretion system (T2SS) which secrets diverse toxins that cause severe diseases such as diarrhea and cholera. GspD needs to translocate from the inner to the outer membrane to exert its function, and this process is an essential step for T2SS to assemble. Here, we investigate two types of secretins discovered so far in Escherichia coli, GspDα, and GspDß. By electron cryotomography subtomogram averaging, we determine in situ structures of key intermediate states of GspDα and GspDß in the translocation process, with resolution ranging from 9 Å to 19 Å. In our results, GspDα and GspDß present entirely different membrane interaction patterns and ways of transitioning the peptidoglycan layer. From this, we hypothesize two distinct models for the membrane translocation of GspDα and GspDß, providing a comprehensive perspective on the inner to outer membrane biogenesis of T2SS secretins.

Truncated glycoprotein E of varicella-zoster virus is an ideal immunogen for Escherichia coli-based vaccine design.

Varicella-zoster virus (VZV) is a highly infectious agent responsible for both varicella and herpes zoster disease. Despite high efficacy, there remain safety and accessibility concerns with the licensed vaccines. Here, we sought to produce a VZV gE immunogen using an E. coli expression system. We found that the soluble expression and yield of gE protein could be enhanced via C-terminal truncations to the protein, thereby facilitating a robust and scalable purification process for the purpose of vaccine manufacturing. The lead truncated gE (aa 31-358), hereafter referred to as tgE, was a homogenous monomer in solution and showed excellent antigenicity. Finally, we assessed and compared the immunogenicity of tgE with commercial vOka LAV and Shingrix vaccine. We found that aluminum-adjuvanted tgE was immunogenic as compared with vOka LAV. When adjuvanted with AS01B, a two-dose immunization of tgE showed comparable or better potency in antibody responses and cell-mediated immunity with those of the Shingrix vaccine at the same dosage, especially in terms of the proportion of IFN-γ-expressing CD4+ T cells. In conclusion, this method of E. coli-mediate tgE expression offers a cost-effective and scalable strategy to generate an ideal VZV gE immunogen for the development of both varicella and zoster vaccines.

In situ structures of secretins from bacterial type II secretion system reveal their membrane interactions and translocation process.

The GspD secretin is the outer membrane channel of the bacterial type II secretion system (T2SS) which secrets diverse effector proteins or toxins that cause severe diseases such as diarrhea and cholera. GspD needs to translocate from the inner to the outer membrane to exert its function, and this process is an essential step for T2SS to assemble. Here, we investigate two types of secretins discovered so far in Escherichia coli , GspD α and GspD ß , respectively. By electron cryotomography subtomogram averaging, we determine in situ structures of all the key intermediate states of GspD α and GspD ß in the translocation process, with resolution ranging from 9 Å to 19 Å. In our results, GspD α and GspD ß present entirely different membrane interaction patterns and ways of going across the peptidoglycan layer. We propose two distinct models for the membrane translocation of GspD α and GspD ß , providing a comprehensive perspective on the inner to outer membrane biogenesis of T2SS secretins.

Using Cryo-ET to distinguish platelets during pre-acute myeloid leukemia from steady state hematopoiesis.

Early diagnosis of acute myeloid leukemia (AML) in the pre-leukemic stage remains a clinical challenge, as pre-leukemic patients show no symptoms, lacking any known morphological or numerical abnormalities in blood cells. Here, we demonstrate that platelets with structurally abnormal mitochondria emerge at the pre-leukemic phase of AML, preceding detectable changes in blood cell counts or detection of leukemic blasts in blood. We visualized frozen-hydrated platelets from mice at different time points during AML development in situ using electron cryo-tomography (cryo-ET) and identified intracellular organelles through an unbiased semi-automatic process followed by quantitative measurement. A large proportion of platelets exhibited changes in the overall shape and depletion of organelles in AML. Notably, 23% of platelets in pre-leukemic cells exhibit abnormal, round mitochondria with unfolded cristae, accompanied by a significant drop in ATP levels and altered expression of metabolism-related gene signatures. Our study demonstrates that detectable structural changes in pre-leukemic platelets may serve as a biomarker for the early diagnosis of AML.

In situ structure of the AcrAB-TolC efflux pump at subnanometer resolution.

The tripartite AcrAB-TolC assembly, which spans both the inner and outer membranes in Gram-negative bacteria, is an efflux pump that contributes to multidrug resistance. Here, we present the in situ structure of full-length Escherichia coli AcrAB-TolC determined at 7 Å resolution by electron cryo-tomography. The TolC channel penetrates the outer membrane bilayer through to the outer leaflet and exhibits two different configurations that differ by a 60° rotation relative to the AcrB position in the pump assembly. AcrA protomers interact directly with the inner membrane and with AcrB via an interface located in proximity to the AcrB ligand-binding pocket. Our structural analysis suggests that these AcrA-bridged interactions underlie an allosteric mechanism for transmitting drug-evoked signals from AcrB to the TolC channel within the pump. Our study demonstrates the power of in situ electron cryo-tomography, which permits critical insights into the function of bacterial efflux pumps.

Antibody-siRNA conjugates (ARCs) using multifunctional peptide as a tumor enzyme cleavable linker mediated effective intracellular delivery of siRNA.

The tissue-specific targeted delivery and efficient cellular uptake of siRNAs are the main obstacles to their clinical application. Antibody-siRNA-conjugates (ARCs) can deliver siRNA by exploiting the targeting property of antibodies like antibody-drug conjugates (ADCs). However, the effective conjugation of antibodies and siRNAs and the release of siRNAs specifically at target sites have posed challenges to the development of ARCs. In this study, the successful conjugation of antibodies and siRNAs was achieved using a multifunctional peptide as a linker, composed of a cell-penetrating peptide (CPP) and a substrate peptide (SP), which is highly expressed in solid tumors. The resulting antibody-multifunctional peptide (SP-CPP)-siRNA system delivered the siRNA to target tumor cells by the specific binding of the antibody. Once the enzymes on the tumor cell surface hydrolyzed the substrate peptide linker, siRNA-CPP was released from ARCs. The released siRNA-CPP entered the targeted cells via the cellular penetrating ability of CPP, resulting in improved siRNA-mediated gene silencing efficiency, verified both in vitro and in vivo. After intravenous administration, the designed ARCs achieved approximately 66.7% EGFP (Enhanced Green Fluorescent Protein) downregulation efficiency in nude mice xenografted with the HCT116-EGFP tumor model. The proposed system provides a prospective choice for ARC production and the safe and efficient delivery of siRNAs.

Neutrophil to lymphocyte ratio as prognostic and predictive factor in patients with coronavirus disease 2019: A retrospective cross-sectional study.

This retrospective study was designed to explore whether neutrophil to lymphocyte ratio (NLR) is a prognostic factor in patients with coronavirus disease 2019 (COVID-19). A cohort of patients with COVID-19 admitted to the Tongren Hospital of Wuhan University from 11 January 2020 to 3 March 2020 was retrospectively analyzed. Patients with hematologic malignancy were excluded. The NLR was calculated by dividing the neutrophil count by the lymphocyte count. NLR values were measured at the time of admission. The primary outcome was all-cause in-hospital mortality. A multivariate logistic analysis was performed. A total of 1004 patients with COVID-19 were included in this study. The mortality rate was 4.0% (40 cases). The median age of nonsurvivors (68 years) was significantly older than survivors (62 years). Male sex was more predominant in nonsurvival group (27; 67.5%) than in the survival group (466; 48.3%). NLR value of nonsurvival group (median: 49.06; interquartile range [IQR]: 25.71-69.70) was higher than that of survival group (median: 4.11; IQR: 2.44-8.12; P < .001). In multivariate logistic regression analysis, after adjusting for confounding factors, NLR more than 11.75 was significantly correlated with all-cause in-hospital mortality (odds ratio = 44.351; 95% confidence interval = 4.627-425.088). These results suggest that the NLR at hospital admission is associated with in-hospital mortality among patients with COVID-19. Therefore, the NLR appears to be a significant prognostic biomarker of outcomes in critically ill patients with COVID-19. However, further investigation is needed to validate this relationship with data collected prospectively.

In situ structure and assembly of the multidrug efflux pump AcrAB-TolC.

Multidrug efflux pumps actively expel a wide range of toxic substrates from the cell and play a major role in intrinsic and acquired drug resistance. In Gram-negative bacteria, these pumps form tripartite assemblies that span the cell envelope. However, the in situ structure and assembly mechanism of multidrug efflux pumps remain unknown. Here we report the in situ structure of the Escherichia coli AcrAB-TolC multidrug efflux pump obtained by electron cryo-tomography and subtomogram averaging. The fully assembled efflux pump is observed in a closed state under conditions of antibiotic challenge and in an open state in the presence of AcrB inhibitor. We also observe intermediate AcrAB complexes without TolC and discover that AcrA contacts the peptidoglycan layer of the periplasm. Our data point to a sequential assembly process in living bacteria, beginning with formation of the AcrAB subcomplex and suggest domains to target with efflux pump inhibitors.

Improved method for synthesis of low molecular weight protamine-siRNA conjugate.

RNAi technology has aroused wide public interest due to its high efficiency and specificity to treat multiple types of diseases. However, the effective delivery of siRNA remains a challenge due to its large molecular weight and strong anionic charge. Considering their remarkable functions in vivo and features that are often desired in drug delivery carriers, biomimetic systems for siRNA delivery become an effective and promising strategy. Based on this, covalent attachment of synthetic cell penetrating peptides (CPP) to siRNA has become of great interest. We developed a monomeric covalent conjugate of low molecular weight protamine (LMWP, a well-established CPP) and siRNA via a cytosol-cleavable disulfide linkage using PEG as a crosslinker. Results showed that the conjugates didn't generate coagulation, and exhibited much better RNAi potency and intracellular delivery compared with the conventional charge-complexed CPP/siRNA aggregates. Three different synthetic and purification methods were compared in order to optimize synthesis efficiency and product yield. The methodology using hetero-bifunctional NHS-PEG-OPSS as a crosslinker to synthesize LMWP-siRNA simplified the synthesis and purification process and produced the highest yield. These results pave the way towards siRNA biomimetic delivery and future clinical translation.

Complete genome sequence of N2-fixing model strain Klebsiella sp. nov. M5al, which produces plant cell wall-degrading enzymes and siderophores.

The bacterial strain M5al is a model strain for studying the molecular genetics of N2-fixation and molecular engineering of microbial production of platform chemicals 1,3-propanediol and 2,3-butanediol. Here, we present the complete genome sequence of the strain M5al, which belongs to a novel species closely related to Klebsiella michiganensis. M5al secretes plant cell wall-degrading enzymes and colonizes rice roots but does not cause soft rot disease. M5al also produces siderophores and contains the gene clusters for synthesis and transport of yersiniabactin which is a critical virulence factor for Klebsiella pathogens in causing human disease. We propose that the model strain M5al can be genetically modified to study bacterial N2-fixation in association with non-legume plants and production of 1,3-propanediol and 2,3-butanediol through degradation of plant cell wall biomass.

Curcumin/sunitinib co-loaded BSA-stabilized SPIOs for synergistic combination therapy for breast cancer.

Coating supermagnetic iron oxide nanoparticles (SPIOs) with albumin would not only improve their in vivo stability but also improve their drug loading capacity, but current methods are either inefficient or time consuming. Herein, a single step synthesis of bovine serum albumin (BSA)-stabilized SPIOs with high dispersity and stability via a modified co-precipitation method is reported. The benefits of albumin for coating of SPIOs, i.e. its long circulation life, low immunogenicity and drug binding ability to specific binding domains, were all retained in our mildly modified BSA. The BSA-SPIOs thus prepared displayed an excellent T2 contrast enhancing effect and drug loading capacity. Two cytotoxic drugs curcumin and sunitinib, where the former is a drug-resistance depressor and the latter is a tyrosine kinase inhibitor, were further co-loaded into the BSA-SPIOs (denoted SPIO-SC) to achieve combined synergistic therapy. SPIO-SC formulations displayed the most significant tumor inhibition yet least drug-induced toxicity both in vitro and in vivo when compared with free drug formulations. Through in vivo pharmacokinetic analysis, it was demonstrated that SPIO-SC most efficiently delivered the encapsulated drugs to the tumor site, and at the same time maintained the originally designed, optimal ratios of curcumin to sunitinib concentrations at the tumor target and yielded the most optimal synergistic effect and, subsequently, the more effective therapeutic outcomes. The prepared BSA-SPIOs are an extremely promising candidate for both MR imaging and drug delivery as a healthcare material.

CPP-Assisted Intracellular Drug Delivery, What Is Next?

For the past 20 years, we have witnessed an unprecedented and, indeed, rather miraculous event of how cell-penetrating peptides (CPPs), the naturally originated penetrating enhancers, help overcome the membrane barrier that has hindered the access of bio-macromolecular compounds such as genes and proteins into cells, thereby denying their clinical potential to become potent anti-cancer drugs. By taking the advantage of the unique cell-translocation property of these short peptides, various payloads of proteins, nucleic acids, or even nanoparticle-based carriers were delivered into all cell types with unparalleled efficiency. However, non-specific CPP-mediated cell penetration into normal tissues can lead to widespread organ distribution of the payloads, thereby reducing the therapeutic efficacy of the drug and at the same time increasing the drug-induced toxic effects. In view of these challenges, we present herein a review of the new designs of CPP-linked vehicles and strategies to achieve highly effective yet less toxic chemotherapy in combating tumor oncology.