Crosstalk between Platelet and Bacteria: A Therapeutic Prospect

From bench to bedside: Platelet biomimetic nanoparticles as a promising carriers for personalized drug delivery

In recent decades, there has been a burgeoning interest in cell membrane coating strategies as innovative approach for targeted delivery systems in biomedical applications. Platelet membrane-coated nanoparticles (PNPs), in particular, are gaining interest as a new route for targeted therapy due to their advantages over conventional drug therapies. Their stepwise approach blends the capabilities of the natural platelet membrane (PM) with the adaptable nature of manufactured nanomaterials, resulting in a synergistic combination that enhances drug delivery and enables the development of innovative therapeutics. In this context, we present an overview of the latest advancements in designing PNPs with various structures tailored for precise drug delivery. Initially, we describe the types, preparation methods, delivery mechanisms, and specific advantages of PNPs. Next, we focus on three critical applications of PNPs in diseases: vascular disease therapy, cancer treatment, and management of infectious diseases. This review presents our knowledge of PNPs, summarizes their advancements in targeted therapies and discusses the promising potential for clinical translation of PNPs.

New insights of platelet endocytosis and its implication for platelet function

Endocytosis constitutes a cellular process in which cells selectively encapsulate surface substances into endocytic vesicles, also known as endosomes, thereby modulating their interaction with the environment. Platelets, as pivotal hematologic elements, play a crucial role not only in regulating coagulation and thrombus formation but also in facilitating tumor invasion and metastasis. Functioning as critical components in the circulatory system, platelets can internalize various endosomal compartments, such as surface receptors, extracellular proteins, small molecules, and pathogens, from the extracellular environment through diverse endocytic pathways, including pinocytosis, phagocytosis, and receptor-mediated endocytosis. We summarize recent advancements in platelet endocytosis, encompassing the catalog of cargoes, regulatory mechanisms, and internal trafficking routes. Furthermore, we describe the influence of endocytosis on platelet regulatory functions and related physiological and pathological processes, aiming to offer foundational insights for future research into platelet endocytosis.

Bacterial Brain Abscesses Expand Despite Effective Antibiotic Treatment: A Process Powered by Osmosis Due to Neutrophil Cell Death

BACKGROUND AND OBJECTIVES

A bacterial brain abscess is an emergency and should be drained of pus within 24 hours of diagnosis, as recently recommended. In this cross-sectional study, we investigated whether delaying pus drainage entails brain abscess expansion and what the underlying mechanism might be.

METHODS

Repeated brain MRI of 47 patients who did not undergo immediate pus drainage, pus osmolarity measurements, immunocytochemistry, proteomics, and 18F-fluorodeoxyglucose positron emission tomography.

RESULTS

Time from first to last MRI before neurosurgery was 1 to 14 days. Abscesses expanded in all but 2 patients: The median average increase was 23% per day (range 0%-176%). Abscesses expanded during antibiotic therapy and even if the pus did not contain viable bacteria. In a separate patient cohort, we found that brain abscess pus tended to be hyperosmolar (median value 360 mOsm; range 266-497; n = 14; normal cerebrospinal fluid osmolarity is ∼290 mOsm). Hyperosmolarity would draw water into the abscess cavity, causing abscess expansion in a ballooning manner through increased pressure in the abscess cavity. A mechanism likely underlying pus hyperosmolarity was the recruitment of neutrophils to the abscess cavity with ensuing neutrophil cell death and decomposition of neutrophil proteins and other macromolecules to osmolytes: Pus analysis showed the presence of neutrophil proteins (protein-arginine deiminases, citrullinated histone, myeloperoxidase, elastase, cathelicidin). Previous studies have shown very high levels of osmolytes (ammonia, amino acids) in brain abscess pus. 18F-fluorodeoxyglucose positron emission tomography showed focal neocortical hypometabolism 1 to 8 years after brain abscess, indicating long-lasting damage to brain tissue.

CONCLUSION

Brain abscesses expand despite effective antibiotic treatment. Furthermore, brain abscesses cause lasting damage to surrounding brain tissue. These findings support drainage of brain abscesses within 24 hours of diagnosis.

Recent advances of cell membrane-coated nanoparticles for therapy of bacterial infection

The rapid evolution of antibiotic resistance and the complicated bacterial infection microenvironments are serious obstacles to traditional antibiotic therapy. Developing novel antibacterial agents or strategy to prevent the occurrence of antibiotic resistance and enhance antibacterial efficiency is of the utmost importance. Cell membrane-coated nanoparticles (CM-NPs) combine the characteristics of the naturally occurring membranes with those of the synthetic core materials. CM-NPs have shown considerable promise in neutralizing toxins, evading clearance by the immune system, targeting specific bacteria, delivering antibiotics, achieving responsive antibiotic released to the microenvironments, and eradicating biofilms. Additionally, CM-NPs can be utilized in conjunction with photodynamic, sonodynamic, and photothermal therapies. In this review, the process for preparing CM-NPs is briefly described. We focus on the functions and the recent advances in applications of several types of CM-NPs in bacterial infection, including CM-NPs derived from red blood cells, white blood cells, platelet, bacteria. CM-NPs derived from other cells, such as dendritic cells, genetically engineered cells, gastric epithelial cells and plant-derived extracellular vesicles are introduced as well. Finally, we place a novel perspective on CM-NPs' applications in bacterial infection, and list the challenges encountered in this field from the preparation and application standpoint. We believe that advances in this technology will reduce threats posed by bacteria resistance and save lives from infectious diseases in the future.

Early platelet level reduction as a prognostic factor in intensive care unit patients with severe aspiration pneumonia

Introduction: This study investigates risk factors underlying the prognosis of severe aspiration pneumonia (SAP) in intensive care unit (ICU) patients and attempts to provide early prognosis reference for clinical tasks. Methods: Patients diagnosed with SAP and admitted to the ICU of Jinshan Hospital, Fudan University, Shanghai, China, between January 2021 and December 2021 were recruited in this retrospective cohort study. Clinical data on a patient's general condition, underlying diseases, laboratory indicators, and 90-day outcomes (survival or death) were recorded. Results: Multivariate logistic regression analysis showed that a low platelet count was an independent risk factor affecting the prognosis of death (OR = 6.68, 95% CI:1.10-40.78, β = 1.90, P = 0.040). Receiver operating characteristic (ROC) curve analysis was used to evaluate the predictive value of variables; cut-off values were calculated and the area under the curve was 0.7782 [(95% CI:0.686-0.871), p < 0.001] for the prediction of death at 90 days in all patients. The Kaplan-Meier curve used for survival analysis showed that, compared with the normal platelet group, the overall survival rate of patients with low platelet levels was significantly lower, and the difference was statistically significant [HR = 2.11, (95% CI:1.47-3.03), p = 0.0001, z = 4.05, X ² = 14.89]. Cox regression analysis, used to further verify the influence of prognostic risk factors, showed that a concurrent low platelet count was the most important independent risk factor affecting the prognosis of SAP (HR = 2.12 [95% CI:1.12-3.99], X² = 50.95, p = 0.021). Conclusion: These findings demonstrate an association between SAP mortality and platelet levels on admission. Thus, platelet level at admission may be used as a readily available marker for assessing the prognosis of patients with SAP.

Platelet Indices Are the Promising Biomarkers in Monitoring Disease Activities in Patients with Syphilis

OBJECTIVE

To uncover the role of the platelet indices in patients with syphilis.

METHODS

A total of 2061 syphilis patients and 528 healthy controls were enrolled in this retrospective cohort study. The data of platelet count (PLT), mean platelet volume (MPV), platelet distribution width (PDW) and indicators of syphilis activities were collected. The correlations between the platelet indices and disease activities were analyzed.

RESULTS

425 (20.6%) of all the 2061 patients were of primary and secondary syphilis, 433 (21.0%) latent, 463 (22.5%) serofast, 350 (17.0%) asymptomatic neurosyphilis and 390 (18.9%) symptomatic neurosyphilis. Compared with the healthy controls, PLT was significantly increased in the primary and secondary syphilis group. Whereas, MPV and PDW were significantly decreased in all stages of syphilis. These changes of platelets indices were reversed after anti-treponemal therapy. Further correlation analysis showed PLT was positively associated with the syphilis activity indicators [rapid plasma reagin (RPR) titer, cerebrospinal fluid white blood cell (CSF-WBC), CSF-protein, and CSF-VDRL (venereal disease research laboratory)] and inflammatory markers [WBC, C-reaction protein (CRP), and erythrocyte sedimentation rate (ESR)]. Conversely, PDW was negatively correlated with all of these parameters. MPV had an inverse relationship with RPR, ESR, and CRP.

CONCLUSIONS

Platelet indices are associated with syphilis activities.

Globulin and albumin to globulin ratio precisely diagnose periprosthetic joint infection and determine the timing of second-stage reimplantation

Background

Periprosthetic joint infection (PJI) is one of the most challenging complications of total joint arthroplasty (TJI). An early and accurate diagnosis of PJI is associated with better treatment outcomes. However, whether the platelet-related markers and globulin-related markers can be used to assist the diagnosis of PJI remains elusive.

Methods

A total of 206 patients who underwent revision hip or knee arthroplasty in our institution were divided into two groups: 79 patients in PJI group and 127 patients in aseptic failure group. The levels of erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), platelet-related markers including platelet count (PLT), mean platelet volume (MPV), plateletcrit (PCT) and PLT to MPV ratio (PMR) and globulin-related markers such as globulin (GLB), albumin to globulin ratio (AGR) and PLT to AGR ratio were compared. The diagnostic value was measured using area under the curve (AUC) after constructing receiver operating characteristic (ROC) curves. The potential of each marker for determining the timing of second-staged reimplantation was also evaluated.

Results

Significantly increased levels of ESR, CRP, PLT, PCT, PMR, GLB and PLT to AGR ratio were identified in PJI group, while decreased levels of MPV and AGR were also found. The diagnostic values of all platelet-related markers and GLB were considered as fair, and good diagnostic values of AGR and PLT to AGR ratio were found, which were comparable to those of ESR and CRP. The levels of GLB and AGR can also be used to predict negative culture result and the timing of second-stage reimplantation.

Conclusions

Globulin and albumin to globulin ratio were found to have good diagnostic values for PJI, and they can precisely predict the culture results and persistent infection.

What Function Do Platelets Play in Inflammation and Bacterial and Viral Infections?

The article presents the function of platelets in inflammation as well as in bacterial and viral infections, which are the result of their reaction with the endovascular environment, including cells of damaged vascular endothelium and cells of the immune system. This role of platelets is conditioned by biologically active substances present in their granules and in their specific structures - EV (extracellular vesicles).

Serum Calcium Level Combined with Platelet Count May Be Useful Indicators for Assisted Diagnosis of Extremity Posttraumatic Osteomyelitis: A Comparative Analysis

Background

A previous study had reported that patients with osteomyelitis (OM) appeared to be more likely to develop hypocalcemia before and after surgery. Calcium sulfate (CS) is frequently used as a local antibiotic vehicle in the treatment of OM, which may also affect serum calcium level. However, whether changes of serum calcium level are caused by OM and/or local use of calcium sulfate remains unclear. Also, platelet (PLT) count plays a crucial predictive role in periprosthetic joint infections (PJIs), but its role in assisted diagnosis of OM is largely unknown. The purpose of this study was to determine whether serum calcium level and PLT count may be helpful in assisted diagnosis of PTOM.

Methods

Between January 2013 and December 2018, we analyzed 468 consecutive patients (392 males and 76 females), including 170 patients with posttraumatic OM (PTOM), 130 patients with aseptic bone nonunion (ABN), and 168 patients recovered from fractures with requirement of implant removal set as controls. Preoperative serological levels of calcium, phosphorus, and PLT were detected, and comparisons were conducted among the above three groups. Additionally, correlations and receiver operating characteristic (ROC) curves were displayed to test whether calcium level and PLT can differentiate patients with ABN and PTOM.

Results

Outcomes showed that the incidences of asymptomatic hypocalcemia (PTOM vs. ABN vs. controls = 22.94% vs. 6.92% vs. 8.82%, χ² = 21.098, P < 0.001) and thrombocytosis (PTOM vs. ABN vs. controls = 35.3% vs. 13.84% vs. 12.35%, χ² = 28.512, P < 0.001) were highest in PTOM patients. Besides, the mean serological levels of phosphorus in PTOM and ABN patients were significantly higher than those in the controls (P = 0.007). The Area Under the Curve (AUC) of the ROC curve outcomes revealed that, with the combination of serum calcium level with PLT count, the predictive role was acceptable (AUC 0.730, P < 0.001, 95% CI 0.681-0.780). Also, serological levels of calcium of 2.225 mmol/L and PLT count of 246.5 × 10⁹/L were identified as the optimal cut-off values to distinguish patients with and without PTOM. However, age- and gender-related differences in serum calcium levels (age, P = 0.056; gender, P = 0.978) and PLT count (age, P = 0.363; gender, P = 0.799) were not found to be statistically significant in any groups. In addition, no significant correlations were identified between serum calcium level and PLT count (R = 0.010, P = 0.839).

Conclusions

Asymptomatic hypocalcemia and thrombocytosis appeared to be more frequent in this cohort with PTOM. Serological levels of calcium and PLT count may be useful biomarkers in screening patients suspected of PTOM.

Platelet-Therapeutics to Improve Tissue Regeneration and Wound Healing-Physiological Background and Methods of Preparation

Besides their function in primary hemostasis, platelets are critically involved in the physiological steps leading to wound healing and tissue repair. For this purpose, platelets have a complex set of receptors allowing the recognition, binding, and manipulation of extracellular structures and the detection of pathogens and tissue damage. Intracellular vesicles contain a huge set of mediators that can be released to the extracellular space to coordinate the action of platelets as other cell types for tissue repair. Therapeutically, the most frequent use of platelets is the intravenous application of platelet concentrates in case of thrombocytopenia or thrombocytopathy. However, there is increasing evidence that the local application of platelet-rich concentrates and platelet-rich fibrin can improve wound healing and tissue repair in various settings in medicine and dentistry. For the therapeutic use of platelets in wound healing, several preparations are available in clinical practice. In the present study we discuss the physiology and the cellular mechanisms of platelets in hemostasis and wound repair, the methods used for the preparation of platelet-rich concentrates and platelet-rich fibrin, and highlight some examples of the therapeutic use in medicine and dentistry.