Demarcation of Sepsis-Induced Peripheral and Central Acidosis with pH (Low) Insertion Cycle Peptide

Control of Inflammatory Response by Tissue Microenvironment

Inflammation is an essential defense response but operates at the cost of normal functions. Whether and how the negative impact of inflammation is monitored remains largely unknown. Acidification of the tissue microenvironment is associated with inflammation. Here we investigated whether macrophages sense tissue acidification to adjust inflammatory responses. We found that acidic pH restructured the inflammatory response of macrophages in a gene-specific manner. We identified mammalian BRD4 as a novel intracellular pH sensor. Acidic pH disrupts the transcription condensates containing BRD4 and MED1, via histidine-enriched intrinsically disordered regions. Crucially, decrease in macrophage intracellular pH is necessary and sufficient to regulate transcriptional condensates in vitro and in vivo, acting as negative feedback to regulate the inflammatory response. Collectively, these findings uncovered a pH-dependent switch in transcriptional condensates that enables environmental sensing to directly control inflammation, with a broader implication for calibrating the magnitude and quality of inflammation by the inflammatory cost.

Factors Associated With Perioperative Hospital Acquired Pressure Injury in Patients Undergoing Spine Surgery in the Prone Position: A Prospective Observational Study

BACKGROUND

Hospital acquired pressure injury (HAPI) is associated with poor clinical outcomes and high medical costs. Patients undergoing surgery in the prone position are particularly vulnerable to perioperative HAPI. This prospective observational study investigated the factors associated with HAPI in patients undergoing elective spine surgery in the prone position.

METHODS

Two hundred eighty-seven patients undergoing elective spine surgery participated in this study. Demographics, perioperative vital signs, laboratory findings, surgical data, and intraoperative data were prospectively recorded. The sites and stages of HAPI were investigated on postoperative day 2. The stages of HAPI were evaluated using the pressure injury staging system of the National Pressure Ulcer Advisory Panel.

RESULTS

Perioperative HAPI was observed in 71 (24.7%) patients (stage 1, 40; stage 2, 31). The most frequent site (number) of HAPI was the upper extremities (33), followed by the chest (32), lower extremities (20), face (18), pelvis (10), and abdomen (9). In multivariate analysis, the duration of prone positioning per hour (odds ratio [95% confidence interval], 1.48 [1.25-1.74]; P <0.001) and intraoperative pH ≤7.35 (1.98 [1.05-3.76]; P =0.036) were associated with perioperative HAPI.

CONCLUSIONS

The incidence of perioperative HAPI was 24.7% in patients undergoing elective spine surgery in the prone position. Long duration of prone positioning and intraoperative acidosis were associated with increased development of perioperative HAPI.

The Recent Advance of Cell-Penetrating and Tumor-Targeting Peptides as Drug Delivery Systems Based on Tumor Microenvironment

Cancer has become the primary reason for industrial countries death. Although first-line treatments have achieved remarkable results in inhibiting tumors, they could have serious side effects because of insufficient selectivity. Therefore, specific localization of tumor cells is currently the main desire for cancer treatment. In recent years, cell-penetrating peptides (CPPs), as a kind of promising delivery vehicle, have attracted much attention because they mediate the high-efficiency import of large quantities of cargos in vivo and vitro. Unfortunately, the poor targeting of CPPs is still a barrier to their clinical application. In order to solve this problem, researchers use the various characteristics of tumor microenvironment and multiple receptors to improve the specificity toward tumors. This review focuses on the characteristics of the tumor microenvironment, and introduces the development of strategies and peptides based on these characteristics as drug delivery system in the tumor-targeted therapy.

pHLIP Peptides Target Acidity in Activated Macrophages

PURPOSE

Acidity can be a useful alternative biomarker for the targeting of metabolically active cells in certain diseased tissues, as in acute inflammation or aggressive tumors. We investigated the targeting of activated macrophages by pH low insertion peptides (pHLIPs), an established technology for targeting cell-surface acidity.

PROCEDURES

The uptake of fluorescent pHLIPs by activated macrophages was studied in cell cultures, in a mouse model of lung inflammation, and in a mouse tumor model. Fluorescence microscopy, whole-body and organ imaging, immunohistochemistry, and FACS analysis were employed.

RESULTS

We find that cultured, activated macrophages readily internalize pHLIPs. The uptake is higher in glycolytic macrophages activated by LPS and INF-γ compared to macrophages activated by IL-4/IL-13. Fluorescent pHLIPs target LPS-induced lung inflammation in mice. In addition to marking cancer cells within the tumor microenvironment, fluorescent pHLIPs target CD45+, CD11b+, F4/80+, and CD206+ tumor-associated macrophages with no significant targeting of other immune cells. Also, fluorescent pHLIPs target CD206-positive cells found in the inguinal lymph nodes of animals inoculated with breast cancer cells in mammary fat pads.

CONCLUSIONS

pHLIP peptides sense low cell surface pH, which triggers their insertion into the cell membrane. Unlike cancerous cells, activated macrophages do not retain inserted pHLIPs on their surfaces, instead their highly active membrane recycling moves the pHLIPs into endosomes. Targeting activated macrophages in diseased tissues may enable clinical visualization and therapeutic opportunities.

Synergism of 64Cu-Labeled RGD with Anti-PD-L1 Immunotherapy for the Long-Acting Antitumor Effect

We put forward a novel targeting-triggering-therapy (TTT) scheme that combines ⁶⁴Cu-based targeted radionuclide therapy (TRT) with programmed death-ligand 1 (PD-L1)-based immunotherapy for enhancing therapeutic efficacy. The α_vβ₃ integrin-targeted ⁶⁴Cu-DOTA-EB-cRGDfK (⁶⁴Cu-DER) was synthesized. Flow cytometry, immunofluorescence staining, and RT-qPCR were performed to verify PD-L1 upregulation after irradiation with ⁶⁴Cu-DER. Positron emission tomography imaging was performed to investigate the prominent tumor retention property of ⁶⁴Cu-DER. In the MC38 tumor model, anti-PD-L1 antibody (αPD-L1 mAb) was delivered in a concurrent or sequential manner after ⁶⁴Cu-DER was injected, followed by the testing of changes in tumor microenvironment (TME). PD-L1 was upregulated in a time- and dose-dependent manner after being induced by ⁶⁴Cu-DER. The combination of ⁶⁴Cu-DER TRT (925 MBq/kg) and αPD-L1 mAb (10 mg/kg) resulted in significant delay in tumor growth and protected against tumor rechallenge. Blockade of PD-L1 at 4 h after ⁶⁴Cu-DER TRT (⁶⁴Cu-DER + αPD-L1 mAb @ 4 h combination group) was able to achieve 100% survival rate, prevent tumor relapse, and evidently prolong the survival of mice. In summary, the combination of ⁶⁴Cu-DER and αPD-L1 mAb in a time-dependent manner could be a promising approach to improve therapeutic efficacy. Understandably, this strategy has the potential to extend the scope of ⁶⁴Cu-based TTT and merits translation into clinical practice for the better management of immune checkpoint blockade immunotherapy.

Thioredoxin-Interacting Protein (TXNIP) Knockdown Protects against Sepsis-Induced Brain Injury and Cognitive Decline in Mice by Suppressing Oxidative Stress and Neuroinflammation

Sepsis-associated encephalopathy (SAE) is linked to increased morbidity and mortality rates in patients with sepsis. Increased cytokine production and neuronal apoptosis are implicated in the pathogenesis of the SAE. Neuroinflammation plays a major role in sepsis-induced brain injury. Thioredoxin-interacting protein (TXNIP), an inhibitor of thioredoxin, is associated with oxidative stress and inflammation. However, whether the TXNIP is involved in the sepsis-induced brain injury and the underlying mechanism is yet to be elucidated. Therefore, the present study was aimed at elucidating the effects of TXNIP knockdown on sepsis-induced brain injury and cognitive decline in mice. Lipopolysaccharide (LPS) was injected intraperitoneally to induce sepsis brain injury in mice. The virus-carrying control or TXNIP shRNA was injected into the lateral ventricle of the brain 4 weeks before the LPS treatment. The histological changes in the hippocampal tissues, encephaledema, and cognitive function were detected, respectively. Also, the 7-day survival rate was recorded. Furthermore, the alterations in microglial activity, oxidative response, proinflammatory factors, apoptosis, protein levels (TXNIP and NLRP3 inflammasome), and apoptosis were examined in the hippocampal tissues. The results demonstrated that the TXNIP and NLRP3 inflammasome expression levels were increased at 6, 12, and 24 h post-LPS injection. TXNIP knockdown dramatically ameliorated the 7-day survival rate, cognitive decline, brain damage, neuronal apoptosis, and the brain water content, inhibited the activation of microglia, downregulated the NLRP3/caspase-1 signaling pathway, and reduced the oxidative stress and the neuroinflammatory cytokine levels at 24 h post-LPS injection. These results suggested a crucial effect of TXNIP knockdown on the mechanism of brain injury and cognitive decline in sepsis mice via suppressing oxidative stress and neuroinflammation. Thus, TXNIP might be a potential therapeutic target for SAE patients.

Studies of cell-penetrating peptides by biophysical methods

Biophysical studies have a very high impact on the understanding of internalization, molecular mechanisms, interactions, and localization of CPPs and CPP/cargo conjugates in live cells or in vivo. Biophysical studies are often first carried out in test-tube set-ups or in vitro, leading to the complicated in vivo systems. This review describes recent studies of CPP internalization, mechanisms, and localization. The multiple methods in these studies reveal different novel and important aspects and define the rules for CPP mechanisms, hopefully leading to their improved applicability to novel and safe therapies.

Controllable membrane remodeling by a modified fragment of the apoptotic protein Bax

Intrinsic apoptosis is orchestrated by a group of proteins that mediate the coordinated disruption of mitochondrial membranes. Bax is a multi-domain protein that, upon activation, disrupts the integrity of the mitochondrial outer membrane by forming pores. We strategically introduced glutamic acids into a short sequence of the Bax protein that constitutively creates membrane pores. The resulting BaxE5 peptide efficiently permeabilizes membranes at acidic pH, showing low permeabilization at neutral pH. Atomic force microscopy (AFM) imaging showed that at acidic pH BaxE5 established several membrane remodeling modalities that progressively disturbed the integrity of the lipid bilayer. The AFM data offers vistas on the membrane disruption process, which starts with pore formation and progresses through localized exposure of membrane monolayers leading to stable and small (height ∼ 16 Å) lipid-peptide complexes. The different types of membrane morphology observed in the presence of BaxE5 suggest that the peptide can establish different types of membrane interactions. BaxE5 adopts a rare unstructured conformation when bound to membranes, which might facilitate the dynamic transition between those different states, and then promote membrane digestion.

In vivo dynamics of acidosis and oxidative stress in the acute phase of an ischemic stroke in a rodent model

Ischemic cerebral stroke is one of the leading causes of death and disability in humans. However, molecular processes underlying the development of this pathology remain poorly understood. There are major gaps in our understanding of metabolic changes that occur in the brain tissue during the early stages of ischemia and reperfusion. In particular, it is generally accepted that both ischemia (I) and reperfusion (R) generate reactive oxygen species (ROS) that cause oxidative stress which is one of the main drivers of the pathology, although ROS generation during I/R was never demonstrated in vivo due to the lack of suitable methods. In the present study, we record for the first time the dynamics of intracellular pH and H2O2 during I/R in cultured neurons and during experimental stroke in rats using the latest generation of genetically encoded biosensors SypHer3s and HyPer7. We detect a buildup of powerful acidosis in the brain tissue that overlaps with the ischemic core from the first seconds of pathogenesis. At the same time, no significant H2O2 generation was found in the acute phase of ischemia/reperfusion. HyPer7 oxidation in the brain was detected only 24 h later. Comparison of in vivo experiments with studies on cultured neurons under I/R demonstrates that the dynamics of metabolic processes in these models significantly differ, suggesting that a cell culture is a poor predictor of metabolic events in vivo.

Tissue Acidosis Associated with Ischemic Stroke to Guide Neuroprotective Drug Delivery

Simple Summary

Ischemic stroke is caused by the blockade of a blood vessel in the brain. Consequently, the brain region supplied by the blocked vessel suffers brain damage and becomes acidic. Here we provide a summary of the causes and consequences of acid accumulation in the brain tissue. Ischemic stroke requires immediate medical attention to minimize the damage of brain tissue, and to save function. It would be desirable for the medical treatment to target the site of injury selectively, to enrich the site of ongoing injury with the protective agent, and to avoid undesirable side effects at the same time. We propose that acid accumulation at the sight of brain tissue injury can be used to delineate the region that would benefit most from medical treatment. Tiny drug carriers known as nanoparticles may be loaded with drugs that protect the brain tissue. These nanoparticles may be designed to release their drug cargo in response to an acidic environment. This would ensure that the therapeutic agent is directed selectively to the site where it is needed. Ultimately, this approach may offer a new way to treat stroke patients with the hope of more effective therapy, and better stroke outcome.

Abstract

Ischemic stroke is a leading cause of death and disability worldwide. Yet, the effective therapy of focal cerebral ischemia has been an unresolved challenge. We propose here that ischemic tissue acidosis, a sensitive metabolic indicator of injury progression in cerebral ischemia, can be harnessed for the targeted delivery of neuroprotective agents. Ischemic tissue acidosis, which represents the accumulation of lactic acid in malperfused brain tissue is significantly exacerbated by the recurrence of spreading depolarizations. Deepening acidosis itself activates specific ion channels to cause neurotoxic cellular Ca²⁺ accumulation and cytotoxic edema. These processes are thought to contribute to the loss of the ischemic penumbra. The unique metabolic status of the ischemic penumbra has been exploited to identify the penumbra zone with imaging tools. Importantly, acidosis in the ischemic penumbra may also be used to guide therapeutic intervention. Agents with neuroprotective promise are suggested here to be delivered selectively to the ischemic penumbra with pH-responsive smart nanosystems. The administered nanoparticels release their cargo in acidic tissue environment, which reliably delineates sites at risk of injury. Therefore, tissue pH-targeted drug delivery is expected to enrich sites of ongoing injury with the therapeutical agent, without the risk of unfavorable off-target effects.