Therapeutic Potential of Cathelicidin Peptide LL-37, an Antimicrobial Agent, in a Murine Sepsis Model

Atomic-Resolution Structures and Mode of Action of Clinically Relevant Antimicrobial Peptides

Global rise of infections and deaths caused by drug-resistant bacterial pathogens are among the unmet medical needs. In an age of drying pipeline of novel antibiotics to treat bacterial infections, antimicrobial peptides (AMPs) are proven to be valid therapeutics modalities. Direct in vivo applications of many AMPs could be challenging; however, works are demonstrating encouraging results for some of them. In this review article, we discussed 3-D structures of potent AMPs e.g., polymyxin, thanatin, MSI, protegrin, OMPTA in complex with bacterial targets and their mode of actions. Studies on human peptide LL37 and de novo-designed peptides are also discussed. We have focused on AMPs which are effective against drug-resistant Gram-negative bacteria. Since treatment options for the infections caused by super bugs of Gram-negative bacteria are now extremely limited. We also summarize some of the pertinent challenges in the field of clinical trials of AMPs.

Therapeutic Role of Antimicrobial Peptides in Diabetes Mellitus

Antimicrobial peptides (AMPs) have recently become widely publicized because they have the potential to function in alternative therapies as “natural” antibiotics, with their main advantage being a broad spectrum of activity. The potential for antimicrobial peptides to treat diabetes mellitus (DM) has been reported. In diabetes mellitus type I (T1D), cathelicidin-related antimicrobial peptide (CRAMP), cathelicidin antimicrobial peptide (CAMP) and mouse-β- defensin 14 (mBD14) are positively affected. Decreased levels of LL-37 and human neutrophil peptide 1-3 (HNP1-3) have been reported in diabetes mellitus type II (T2D) relative to healthy patients. Moreover, AMPs from amphibians and social wasps have antidiabetic effects. In infections occurring in patients with tuberculosis-diabetes or diabetic foot, granulysin, HNP1, HNP2, HNP3, human beta-defensin 2 (HBD2), and cathelicidins are responsible for pathogen clearance. An interesting alternative is also the use of modified M13 bacteriophages containing encapsulated AMPs genes or phagemids.

Predicting Diagnostic Gene Biomarkers Associated With Immune Checkpoints, N6-Methyladenosine, and Ferroptosis in Patients With Acute Myocardial Infarction

This study aimed to determine early diagnosis genes of acute myocardial infarction (AMI) and then validate their association with ferroptosis, immune checkpoints, and N6-methyladenosine (m6A), which may provide a potential method for the early diagnosis of AMI. Firstly, we downloaded microarray data from NCBI (GSE61144, GSE60993, and GSE42148) and identified differentially expressed genes (DEGs) in samples from healthy subjects and patients with AMI. Also, we performed systematic gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses and used STRING to predict protein interactions. Moreover, MCC and MCODE algorithms in the cytoHubba plug-in were used to screen nine key genes in the network. We then determined the diagnostic significance of the nine obtained DEGs by plotting receiver operating characteristic curves using a multiscale curvature classification algorithm. Meanwhile, we investigated the relationship between AMI and immune checkpoints, ferroptosis, and m6A. In addition, we further validated the key genes through the GSE66360 dataset and consequently obtained nine specific genes that can be used as early diagnosis biomarkers for AMI. Through screening, we identified 210 DEGs, including 53 downregulated and 157 upregulated genes. According to GO, KEGG, and key gene screening results, FPR1, CXCR1, ELANE, TLR2, S100A12, TLR4, CXCL8, FPR2 and CAMP could be used for early prediction of AMI. Finally, we found that AMI was associated with ferroptosis, immune checkpoints, and m6A and FPR1, CXCR1, ELANE, TLR2, S100A12, TLR4, CXCL8, FPR2 and CAMP are effective markers for the diagnosis of AMI, which can provide new prospects for future studies on the pathogenesis of AMI.

Mechanism of Antimicrobial Peptides: Antimicrobial, Anti-Inflammatory and Antibiofilm Activities

Antimicrobial peptides (AMPs) are regarded as a new generation of antibiotics. Besides antimicrobial activity, AMPs also have antibiofilm, immune-regulatory, and other activities. Exploring the mechanism of action of AMPs may help in the modification and development of AMPs. Many studies were conducted on the mechanism of AMPs. The present review mainly summarizes the research status on the antimicrobial, anti-inflammatory, and antibiofilm properties of AMPs. This study not only describes the mechanism of cell wall action and membrane-targeting action but also includes the transmembrane mechanism of intracellular action and intracellular action targets. It also discusses the dual mechanism of action reported by a large number of investigations. Antibiofilm and anti-inflammatory mechanisms were described based on the formation of biofilms and inflammation. This study aims to provide a comprehensive review of the multiple activities and coordination of AMPs in vivo, and to fully understand AMPs to realize their therapeutic prospect.

Antimicrobial peptides: mechanism of action, activity and clinical potential

The management of bacterial infections is becoming a major clinical challenge due to the rapid evolution of antibiotic resistant bacteria. As an excellent candidate to overcome antibiotic resistance, antimicrobial peptides (AMPs) that are produced from the synthetic and natural sources demonstrate a broad-spectrum antimicrobial activity with the high specificity and low toxicity. These peptides possess distinctive structures and functions by employing sophisticated mechanisms of action. This comprehensive review provides a broad overview of AMPs from the origin, structural characteristics, mechanisms of action, biological activities to clinical applications. We finally discuss the strategies to optimize and develop AMP-based treatment as the potential antimicrobial and anticancer therapeutics.

Efficacy of graphene oxide-loaded cationic antimicrobial peptide AWRK6 on the neutralization of endotoxin activity and in the treatment of sepsis

Objective: This study is to assess the therapeutic effect of graphene oxide (GO) loaded with AWRK6 on endotoxin-induced sepsis.

Method: AWRK6/GO was prepared by GO loaded AWRK6, with the structure characterization of AWRK6/GO conducted by atomic force microscope (AFM) and ultraviolet spectrophotometer, the sustained release rate of AWRK6/GO detected by high performance liquid chromatography (HPLC), and the neutralization ability of AWRK6/GO to lipopolysaccharide (LPS) tested by in vitro experiments. The levels of IL-8 and TNF-α in mouse cells after drug intervention were detected by ELISA; a LPS mouse model was established to observe the effects of drug intervention on the survival cycle and survival rate of mice.

Results: The sustained drug release rate of AWRK6/GO reached 85% within 24 hours observed under in vitro conditions, with an efficient neutralization effect to LPS (P < 0.01); Compared with the control group, the intervention of LPS succeeded in remarkably elevating the levels of IL-8 and TNF-α in the whole blood and macrophages of the mice (P < 0.01), whose survival cycle and survival rate consequently observed an obvious decline (P < 0.01); The intervention with AWRK6 or AWRK6/GO predominantly brought down the levels of IL-8 and TNF-α in the whole blood and macrophages of mice given LPS (P < 0.01), resulting in an elevation of the survival rate and survival time (P < 0.01).

Conclusion: GO loaded with cationic antimicrobial peptide AWRK6 exerts a rosy neutralization effect on endotoxin activity, with no obvious side effects on mice observed, which is of certain application value in the treatment of sepsis.

The Role and Mechanism of Pyroptosis and Potential Therapeutic Targets in Sepsis: A Review

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Recently was been found that pyroptosis is a unique form of proinflammatory programmed death, that is different from apoptosis. A growing number of studies have investigated pyroptosis and its relationship with sepsis, including the mechanisms, role, and relevant targets of pyroptosis in sepsis. While moderate pyroptosis in sepsis can control pathogen infection, excessive pyroptosis can lead to a dysregulated host immune response and even organ dysfunction. This review provides an overview of the mechanisms and potential therapeutic targets underlying pyroptosis in sepsis identified in recent decades, looking forward to the future direction of treatment for sepsis.

Remineralising dentine caries using an artificial antimicrobial peptide: An in vitro study

OBJECTIVE

To investigate the antibacterial and remineralising effects of a novel dual-action antimicrobial peptide, GA-KR12, on artificial dentine caries.

METHODS

Human dentine blocks with artificial carious lesions were allocated to two groups - Group 1: dentine blocks treated with the novel antimicrobial peptide GA-KR12 twice daily; Group 2: dentine blocks received water as the negative control. Two groups underwent Streptococcus mutan biofilm-remineralisation cycles at 37 °C for 7 days. The morphology, viability and growth kinetics of the S. mutans biofilm were evaluated by scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and colony-forming unit (CFU) counting, respectively. The dentine blocks' lesion depths and mineral loss, changes in chemical structure, dentine surface morphology and crystal characteristics were determined using micro-computed tomography, Fourier transform infrared (FTIR), SEM and X-ray diffraction (XRD), respectively.

RESULTS

The surface of the dentine blocks in Group 1 was partially covered by S. mutans with damaged cell structure. Group 2 showed affluent growth of S. mutans covering the dentine surface when compared to Group 1. The dead-to-live ratio of Group 1 and Group 2 were 0.78 ± 0.01 and 0.47 ± 0.08, respectively (p < 0.001). The Log CFUs of Group 1 and Group 2 were 7.14 ± 0.30 and 8.24 ± 0.20, respectively (p < 0.001). The lesion depths of Group 1 and Group 2 were 109 ± 1 µm and 135 ± 3 µm, respectively (p < 0.001). The mineral loss of Group 1 and Group 2 were 0.59 ± 0.08 gHApcm^-3 and 0.81 ± 0.07 gHApcm^-3, respectively (p < 0.001). FTIR showed the amide I-to-hydrogen phosphate (HPO₄^2-) ratios of Group 1 and Group 2 were 0.25 ± 0.05 and 0.39 ± 0.05 (p < 0.001), respectively. SEM images showed Group 1 had less exposed dentine collagen fibres than Group 2. The XRD revealed that the hydroxyapatite in Group 1 was well crystalised.

CONCLUSION

This study demonstrated that the novel antimicrobial peptide GA-KR12 inhibited the growth of S. mutans biofilm and enhanced the remineralisation of artificial dentine caries.

Outstanding Contributions of LAL Technology to Pharmaceutical and Medical Science: Review of Methods, Progress, Challenges, and Future Perspectives in Early Detection and Management of Bacterial Infections and Invasive Fungal Diseases

The blue blood of the horseshoe crab is a natural, irreplaceable, and precious resource that is highly valued by the biomedical industry. The Limulus amebocyte lysate (LAL) obtained from horseshoe crab blood cells functions as a surprisingly sophisticated sensing system that allows for the extremely sensitive detection of bacterial and fungal cell-wall components. Notably, LAL tests have markedly contributed to the quality control of pharmaceutical drugs and medical devices as successful alternatives to the rabbit pyrogen test. Furthermore, LAL-based endotoxin and (1→3)-β-D-glucan (β-glucan) assay techniques are expected to have optimal use as effective biomarkers, serving as adjuncts in the diagnosis of bacterial sepsis and fungal infections. The innovative β-glucan assay has substantially contributed to the early diagnosis and management of invasive fungal diseases; however, the clinical significance of the endotoxin assay remains unclear and is challenging to elucidate. Many obstacles need to be overcome to enhance the analytical sensitivity and clinical performance of the LAL assay in detecting circulating levels of endotoxin in human blood. Additionally, there are complex interactions between endotoxin molecules and blood components that are attributable to the unique physicochemical properties of lipopolysaccharide (LPS). In this regard, while exploring the potential of new LPS-sensing technologies, a novel platform for the ultrasensitive detection of blood endotoxin will enable a reappraisal of the LAL assay for the highly sensitive and reliable detection of endotoxemia.

Cathelicidin antimicrobial peptide (CAMP) gene promoter methylation induces chondrocyte apoptosis

Objective

The occurrence of osteoarthritis is related to genetic and environmental factors. Among them, the change of chondrocyte gene expression pattern regulated by epigenetic modification is an important participant. This study analyzed the effect of CAMP gene methylation on the level of oxidative stress and inflammation of chondrocytes.

Methods

We analyzed the changes of the transcriptome in the articular cartilage tissue of osteoarthritis (OA) patients from the GSE117999 dataset. The GSE48422 dataset was used to analyze the changes in the methylation level of osteoarthritis cells. Cell Counting Kit-8 (CCK-8) and flow cytometry analysis of short hairpin RNA (shRNA) silencing CAMP gene and 5-μM 5-Aza-2’-Deoxycytidine (AZA) treatment on the proliferation and apoptosis of Human chondrocytes osteoarthritis (HC-OA) cells. The Dichloro-dihydro-fluorescein diacetate (DCFH-DA) assay was used to detect the level of reactive oxygen species (ROS), and the expression level of inflammatory factors was analyzed by Western Blot.

Results

The expression of CAMP in cartilage tissue of OA patients was upregulated, and the level of methylation was downregulated. CAMP was highly expressed in osteoarthritis articular cartilage cells. Silencing CAMP inhibited the proliferation of HC-OA cells and promoted their apoptosis. CAMP gene methylation inhibited ROS levels and tumor necrosis factor-α (TNF-α) expression levels in HC-OA cells, and promoted transforming growth factor beta (TGF-β) expression. CAMP gene methylation inhibited the proliferation of HC-OA cells and promoted their apoptosis.

Conclusion

CAMP gene promoter methylation inhibits ROS levels and inflammation and induces chondrocyte apoptosis.