Single administration of p2TA (AB103), a CD28 antagonist peptide, prevents inflammatory and thrombotic reactions and protects against gastrointestinal injury in total-body irradiated mice

Antimicrobial peptides: Opportunities and challenges in overcoming resistance

Antibiotic resistance represents a global health threat, challenging the efficacy of traditional antimicrobial agents and necessitating innovative approaches to combat infectious diseases. Among these alternatives, antimicrobial peptides have emerged as promising candidates against resistant pathogens. Unlike traditional antibiotics with only one target, these peptides can use different mechanisms to destroy bacteria, with low toxicity to mammalian cells compared to many conventional antibiotics. Antimicrobial peptides (AMPs) have encouraging antibacterial properties and are currently employed in the clinical treatment of pathogen infection, cancer, wound healing, cosmetics, or biotechnology. This review summarizes the mechanisms of antimicrobial peptides against bacteria, discusses the mechanisms of drug resistance, the limitations and challenges of AMPs in peptide drug applications for combating drug-resistant bacterial infections, and strategies to enhance their capabilities.

Antimicrobial resistance crisis: could artificial intelligence be the solution?

Antimicrobial resistance is a global public health threat, and the World Health Organization (WHO) has announced a priority list of the most threatening pathogens against which novel antibiotics need to be developed. The discovery and introduction of novel antibiotics are time-consuming and expensive. According to WHO's report of antibacterial agents in clinical development, only 18 novel antibiotics have been approved since 2014. Therefore, novel antibiotics are critically needed. Artificial intelligence (AI) has been rapidly applied to drug development since its recent technical breakthrough and has dramatically improved the efficiency of the discovery of novel antibiotics. Here, we first summarized recently marketed novel antibiotics, and antibiotic candidates in clinical development. In addition, we systematically reviewed the involvement of AI in antibacterial drug development and utilization, including small molecules, antimicrobial peptides, phage therapy, essential oils, as well as resistance mechanism prediction, and antibiotic stewardship.

The homodimer interfaces of costimulatory receptors B7 and CD28 control their engagement and pro-inflammatory signaling

BACKGROUND

The inflammatory response is indispensable for protective immunity, yet microbial pathogens often trigger an excessive response, 'cytokine storm', harmful to the host. Full T-cell activation requires interaction of costimulatory receptors B7-1(CD80) and B7-2(CD86) expressed on antigen-presenting cells with CD28 expressed on the T cells. We created short peptide mimetics of the homodimer interfaces of the B7 and CD28 receptors and examined their ability to attenuate B7/CD28 coligand engagement and signaling through CD28 for inflammatory cytokine induction in human immune cells, and to protect from lethal toxic shock in vivo.

METHODS

Short B7 and CD28 receptor dimer interface mimetic peptides were synthesized and tested for their ability to attenuate the inflammatory cytokine response of human peripheral blood mononuclear cells, as well as for their ability to attenuate B7/CD28 intercellular receptor engagement. Mice were used to test the ability of such peptides to protect from lethal superantigen toxin challenge when administered in molar doses far below the toxin dose.

RESULTS

B7 and CD28 homodimer interfaces are remote from the coligand binding sites, yet our finding is that by binding back into the receptor dimer interfaces, short dimer interface mimetic peptides inhibit intercellular B7-2/CD28 as well as the tighter B7-1/CD28 engagement, attenuating thereby pro-inflammatory signaling. B7 mimetic peptides exhibit tight selectivity for the cognate receptor in inhibiting intercellular receptor engagement with CD28, yet each diminishes signaling through CD28. In a prominent example of inflammatory cytokine storm, by attenuating formation of the B7/CD28 costimulatory axis, B7-1 and CD28 dimer interface mimetic peptides protect mice from lethal toxic shock induced by a bacterial superantigen even when administered in doses far submolar to the superantigen.

CONCLUSIONS

Our results reveal that the B7 and CD28 homodimer interfaces each control B7/CD28 costimulatory receptor engagement and highlight the protective potential against cytokine storm of attenuating, yet not ablating, pro-inflammatory signaling via these receptor domains.

Advances in pharmacotherapy for acute kidney injury

INTRODUCTION

Acute kidney injury (AKI) is a clinically critical disease exhibiting an acute decline in renal function. The lack of an effective prevention and treatment method equates to a high morbidity and mortality rate. Consequently, over the past few decades, many therapeutic drugs with different mechanisms of action have been proposed and gradually applied to the clinic. The involved drug mechanisms evaluated have included hemodynamic modulation, anti-inflammatory, antioxidant, repair agents, metabolic derangement and mitochondrial function.

AREAS COVERED

The authors of this review provide the reader with a reference point for the latest advances in pharmacotherapy in acute kidney injury. This is achieved by the evaluation of the latest data collected on potential therapeutic drugs with different mechanisms of action, as well as their preclinical and clinical impact on AKI.

EXPERT OPINION

Presently, the vast majority of drugs are still in clinical development, which is a huge challenge. Nevertheless, in addition to current chemical drugs and gene therapy strategies, the advent of mesenchymal stem cell treatments and other emerging pharmaceutical strategies could enable clinicians to better treat AKI. Due to the nonselective distribution and low bioavailability of some of the latest pharmaceutical strategies, there is hope that these treatment options may provide more efficacious avenues.

Radiotherapy-Induced Digestive Injury: Diagnosis, Treatment and Mechanisms

Radiotherapy is one of the main therapeutic methods for treating cancer. The digestive system consists of the gastrointestinal tract and the accessory organs of digestion (the tongue, salivary glands, pancreas, liver and gallbladder). The digestive system is easily impaired during radiotherapy, especially in thoracic and abdominal radiotherapy. In this review, we introduce the physical classification, basic pathogenesis, clinical characteristics, predictive/diagnostic factors, and possible treatment targets of radiotherapy-induced digestive injury. Radiotherapy-induced digestive injury complies with the dose-volume effect and has a radiation-based organ correlation. Computed tomography (CT), MRI (magnetic resonance imaging), ultrasound (US) and endoscopy can help diagnose and evaluate the radiation-induced lesion level. The latest treatment approaches include improvement in radiotherapy (such as shielding, hydrogel spacers and dose distribution), stem cell transplantation and drug administration. Gut microbiota modulation may become a novel approach to relieving radiogenic gastrointestinal syndrome. Finally, we summarized the possible mechanisms involved in treatment, but they remain varied. Radionuclide-labeled targeting molecules (RLTMs) are promising for more precise radiotherapy. These advances contribute to our understanding of the assessment and treatment of radiation-induced digestive injury.

A hypothesis: radiation carcinogenesis may result from tissue injuries and subsequent recovery processes which can act as tumor promoters and lead to an earlier onset of cancer

Cancer risks from radiation can be observed as an increase in mortality when compared to a control group. However, it is unknown if this increased risk results from the induction of cancer or from an earlier onset of cancer. In mouse studies, it has been repeatedly shown that after an irradiation, the survival curve is shifted toward lower ages, but remains parallel to the control curve, and the extent of the shift in time to lower ages is dose-dependent. This shift is not satisfactorily explained by the induction model which assumes that cancers in the exposed group consist of spontaneous and induced events. Consequently, it seems that this shift could be interpreted to mean that all animals in the exposed group had suffered from life shortening. Under this scenario, however, it turns out that the radiation effects can no longer be interpreted as the result of oncogenic mutations, because these effects would have to involve all tumors, and the effectiveness of radiation changes with the dose. This leads to the speculation that radiation exposures induce a broad range of tissue injuries, and that these injuries are subsequently subjected to longlasting systemic recovery processes which act as promoters for tumor cells. In other words, potential cancer stem cells which were located in the irradiated field can escape oncogenic damage but undergo stimulation later in life toward the development of malignancy from radiation-induced activated microenvironment. This is an unusual form of the non-targeted or bystander effects of radiation. It is worth noting that this model suggests that there could be a path or paths which could be used to intervene in the process of post-exposure carcinogenesis, and that cancer risks at low doses could be described as days or weeks of life lost.

CD28 Deficiency Ameliorates Blast Exposure-Induced Lung Inflammation, Oxidative Stress, Apoptosis, and T Cell Accumulation in the Lungs via the PI3K/Akt/FoxO1 Signaling Pathway

Although CD28 is associated with the expression of inflammatory mediators, apoptosis-related protein, immunosuppression, and tumorigenesis, the effects of CD28 deficiency on blast exposure-induced lung injury have not been investigated. In this study, we have explored the effects of CD28 on blast exposure-induced lung injury and studied its potential molecular mechanisms. A mouse model of blast exposure-induced acute lung injury was established. Sixty C57BL/6 wild-type (WT) and CD28 knockout (CD28^−/−) mice were randomly divided into control or model groups. Lung tissue samples were collected 24 h and 48 h after blast injury. Histopathological changes and the expressions of inflammatory-related proteins were detected by hematoxylin-eosin, immunohistochemistry, and immunofluorescence staining. Apoptosis and oxidative stress were evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining and reactive oxygen species (ROS). Inflammation, apoptosis, oxidative stress, and related pathway protein expression were studied by western blotting. In addition, the levels of CD3 and CD28 proteins were measured by flow cytometry. In the current study, we found that CD28 deficiency significantly inhibited blast exposure-induced increases in the lung weight/body weight ratio and wet weight/dry weight ratio; decreased the infiltration of CD44⁺ leukocytes, CD163⁺ macrophages, and CD3⁺ T cells into the lungs; reduced the expressions of proinflammatory cytokines including IL-1β, TNF-α, and IL-6; and markedly increased IL-10 expression. CD28 deficiency also significantly attenuated blast exposure-induced ROS, MDA5, and IREα expressions; increased SOD-1 expression; lowered the number of apoptotic cells and Bax, Caspase-3, and active Caspase-8 expressions; and increased Bcl-2 expression. Additionally, CD28 deficiency significantly ameliorated blast exposure-induced increases of p-PI3K and p-Akt and ameliorated the decrease in the p-FoxO1 expression. Our results suggest that CD28 deficiency has a protective effect on blast exposure-induced lung injury, which might be associated with the PI3K/Akt/FoxO1 signaling pathway.

CD28 Deficiency Ameliorates Thoracic Blast Exposure-Induced Oxidative Stress and Apoptosis in the Brain through the PI3K/Nrf2/Keap1 Signaling Pathway

Blast exposure is a worldwide public health concern, but most related research has been focused on direct injury. Thoracic blast exposure-induced neurotrauma is a type of indirect injuries where research is lacking. As CD28 stimulates T cell activation and survival and contributes to inflammation initiation, it may play a role in thoracic blast exposure-induced neurotrauma. However, it has not been investigated. To explore the effects of CD28 on thoracic blast exposure-induced brain injury and its potential molecular mechanisms, a mouse model of thoracic blast exposure-induced brain injury was established. Fifty C57BL/6 wild-type (WT) and fifty CD28 knockout (CD28^-/-) mice were randomly divided into five groups (one control group and four model groups), with ten mice (from each of the two models) for each group. Lung and brain tissue and serum samples were collected at 12 h, 24 h, 48 h, and 1 week after thoracic blast exposure. Histopathological changes were detected by hematoxylin-eosin staining. The expressions of inflammatory-related factors were detected by ELISA. Oxidative stress in the brain tissue was evaluated by determining the generation of reactive oxygen species (ROS) and the expressions of thioredoxin (TRX), malondialdehyde (MDA), SOD-1, and SOD-2. Apoptosis in the brain tissue was evaluated by TUNEL staining and the levels of Bax, Bcl-xL, Bad, Cytochrome C, and caspase-3. In addition, proteins of related pathways were also studied by western blotting and immunofluorescence. We found that CD28 deficiency significantly reduced thoracic blast exposure-induced histopathological changes and decreased the levels of inflammatory-related factors, including IL-1β, TNF-α, and S100β. In the brain tissue, CD28 deficiency also significantly attenuated thoracic blast exposure-induced generation of ROS and expressions of MDA, TRX, SOD-1, and SOD-2; lowered the number of apoptotic cells and the expression of Bax, cleaved caspase-3, Cytochrome C, and Bad; and maintained Bcl-xL expression. Additionally, CD28 deficiency significantly ameliorated thoracic blast exposure-induced increases of p-PI3K and Keap1 and the decrease of Nrf2 expression in the brain. Our results indicate that CD28 deficiency has a protective effect on thoracic blast exposure-induced brain injury that might be associated with the PI3K/Nrf2/Keap1 signaling pathway.

CD28 Costimulation: From Mechanism to Therapy

Ligation of the CD28 receptor on T cells provides a critical second signal alongside T cell receptor (TCR) ligation for naive T cell activation. Here, we discuss the expression, structure, and biochemistry of CD28 and its ligands. CD28 signals play a key role in many T cell processes, including cytoskeletal remodeling, production of cytokines, survival, and differentiation. CD28 ligation leads to unique epigenetic, transcriptional, and post-translational changes in T cells that cannot be recapitulated by TCR ligation alone. We discuss the function of CD28 and its ligands in both effector and regulatory T cells. CD28 is critical for regulatory T cell survival and the maintenance of immune homeostasis. We outline the roles that CD28 and its family members play in human disease and we review the clinical efficacy of drugs that block CD28 ligands. Despite the centrality of CD28 and its family members and ligands to immune function, many aspects of CD28 biology remain unclear. Translation of a basic understanding of CD28 function into immunomodulatory therapeutics has been uneven, with both successes and failures. Such real-world results might stem from multiple factors, including complex receptor-ligand interactions among CD28 family members, differences between the mouse and human CD28 families, and cell-type specific roles of CD28 family members.

Des-Aspartate-Angiotensin I Attenuates Mortality of Mice Exposed to Gamma Radiation via a Novel Mechanism of Action

ACE inhibitors and ARBs (angiotensin receptor blockers) have been shown to attenuate radiation injuries in animal models of lethal gamma irradiation. These two classes of drug act by curtailing the actions of angiotensin II-linked inflammatory pathways that are up-regulated during gamma radiation in organ systems such as the brain, lung, kidney, and bone marrow. ACE inhibitors inhibit ACE and attenuate the formation of angiotensin II from angiotensin I; ARBs block the angiotensin AT1 receptor and attenuate the actions of angiotensin II that are elicited through the receptor. DAA-I (des-aspartate-angiotensin I), an orally active angiotensin peptide, also attenuates the deleterious actions of angiotensin II. It acts as an agonist on the angiotensin AT1 receptor and elicits responses that oppose those of angiotensn II. Thus, DAA-I was investigated for its anticipated radioprotection in gamma irradiated mice. DAA-I administered orally at 800 nmole/kg/day for 30 days post exposure (6.4 Gy) attenuated the death of mice during the 30-day period. The attenuation was blocked by losartan (50 nmole/kg/day, i.p.) that was administered sequential to DAA-I administration. This shows that the radioprotection was mediated via the angiotensin AT1 receptor. Furthermore, the radioprotection correlated to an increase in circulating PGE2 of surviving animals, and this suggests that PGE2 is involved in the radioprotection in DAA-I-treated mice. At the hematopoietic level, DAA-I significantly improved two syndromes of myelosuppression (leucopenia and lymphocytopenia), and mice pre-treated with DAA-I prior to gamma irradiation showed significant improvement in the four myelodysplastic syndromes that were investigated, namely leucopenia, lymphocytopenia, monocytopenia and thrombocytopenia. Based on the known ability of PGE2 to attenuate the loss of functional hematopoietic stem and progenitor cells in radiation injury, we hypothesize that PGE2 mediated the action of DAA-I. DAA-I completely attenuated the increase in circulating level of two inflammatory cytokines, TNFα and IL-6, in irradiated mice; and this shows that DAA-I exerted additional anti-inflammatory actions, which could also have contributed to its radioprotection. These findings show that DAA-I acts via a novel mechanism of action on the angiotensin AT1 receptor to specifically release PGE2, which mediates radioprotection in the gamma irradiated mice.