Caspase inhibitors

Golgi dispersal in cancer stem cells promotes chemoresistance of colorectal cancer via the Golgi stress response

Chemotherapy is a crucial treatment for colorectal tumors. However, its efficacy is restricted by chemoresistance. Recently, Golgi dispersal has been suggested to be a potential response to chemotherapy, particularly to drugs that induce DNA damage. However, the underlying mechanisms by which Golgi dispersal enhances the capacity to resist DNA-damaging agents remain unclear. Here, we demonstrated that DNA-damaging agents triggered Golgi dispersal in colorectal cancer (CRC), and cancer stem cells (CSCs) possessed a greater degree of Golgi dispersal compared with differentiated cancer cells (non-CSCs). We further revealed that Golgi dispersal conferred resistance against the lethal effects of DNA-damaging agents. Momentously, Golgi dispersal activated the Golgi stress response via the PKCα/GSK3α/TFE3 axis, resulting in enhanced protein and vesicle trafficking, which facilitated drug efflux through ABCG2. Identification of Golgi dispersal indicated an unexpected pathway regulating chemoresistance in CRC.

Pyroptosis: Mechanisms and links with diabetic cardiomyopathy

Diabetes mellitus (DM) is a chronic metabolic disease characterized by hyperglycaemia that seriously affects human health. Diabetic cardiomyopathy (DCM) is a major cardiovascular complication and one of the main causes of death in patients with DM. Although DCM attracts great attention, and new therapeutic methods are continuously developed, there is a lack of effective treatment strategies. Therefore, exploring and targeting new signalling pathways related to the evolution of DCM becomes a hotspot and difficulty in the prevention and treatment of DCM. Pyroptosis is a newly discovered regulated cell death that is heavily dependent on the formation of plasma membrane pores by members of the gasdermin protein family and is reported to be involved in the occurrence, development, and pathogenesis of DCM. In this review, we focus on the molecular mechanisms of pyroptosis, its involvement in the relevant signalling pathways of DCM, and potential pyroptosis-targeting therapeutic strategies for the treatment of DCM. Our review provides new insights into the use of pyroptosis as a useful tool for the prevention and treatment of DCM and clarifies future research directions.

Interleukin-1β converting enzyme (ICE): A comprehensive review on discovery and development of caspase-1 inhibitors

Caspase-1 is a critical mediator of the inflammatory process by activating various pro-inflammatory cytokines such as pro-IL-1β, IL-18 and IL-33. Uncontrolled activation of caspase-1 leads to various cytokines-mediated diseases. Thus, inhibition of Caspase-1 is considered therapeutically beneficial to halt the progression of such diseases. Currently, rilonacept, canakinumab and anakinra are in use for caspase-1-mediated autoinflammatory diseases. However, the poor pharmacokinetic profile of these peptides limits their use as therapeutic agents. Therefore, several peptidomimetic inhibitors have been developed, but only a few compounds (VX-740, VX-765) have advanced to clinical trials; because of their toxic profile. Several small molecule inhibitors have also been progressing based on the three-dimensional structure of caspase-1. However there is no successful candidate available clinically. In this perspective, we highlight the mechanism of caspase-1 activation, its therapeutic potential as a disease target and potential therapeutic strategies targeting caspase-1 with their limitations.

Mechanisms of NLRP3 inflammasome activation and the development of peptide inhibitors

The Nucleotide-binding domain leucine-rich repeat and pyrin domain containing receptor 3 (NLRP3), a member of the nucleotide-binding oligomerization domain (NOD) like receptors (NLRs) family, plays an important role in the innate immune response against pathogen invasions. NLRP3 inflammasome consisting of NLRP3 protein, the adapter protein apoptosis-associated speck-like protein containing a caspase recruitment domain (CARD) (ASC), and the effector protein pro-caspase-1, is central to this process. Upon activation, NLRP3 inflammasome initiates the release of inflammatory cytokines and triggers a form of cell death known as pyroptosis. Dysregulation or inappropriate activation of NLRP3 has been implicated in various human diseases, including type 2 diabetes, colitis, depression, and gout. Consequently, understanding the mechanism underlying NLRP3 inflammasome activation is critical for the development of therapeutic drugs. In the pursuit of potential therapeutic agents, peptides present several advantages over small molecules. They offer higher selectivity, increased potency, reduced toxicity, and fewer off-target effects. The advancements in molecular biology have expanded the opportunities for applying peptides in medicine, unlocking their vast medical potential. This review begins by providing a comprehensive summary of recent research progress regarding the mechanisms governing NLRP3 inflammasome activation. Subsequently, we offer an overview of current peptide inhibitors capable of modulating the NLRP3 inflammasome activation pathway.

Inhibition of GSDMD activation by Z-LLSD-FMK or Z-YVAD-FMK reduces vascular inflammation and atherosclerotic lesion development in ApoE-/- mice

Pyroptosis is a form of pro-inflammatory cell death that can be mediated by gasdermin D (GSDMD) activation induced by inflammatory caspases such as caspase-1. Emerging evidence suggests that targeting GSDMD activation or pyroptosis may facilitate the reduction of vascular inflammation and atherosclerotic lesion development. The current study investigated the therapeutic effects of inhibition of GSDMD activation by the novel GSDMD inhibitor N-Benzyloxycarbonyl-Leu-Leu-Ser-Asp(OMe)-fluoromethylketone (Z-LLSD-FMK), the specific caspase-1 inhibitor N-Benzyloxycarbonyl-Tyr-Val-Ala-Asp(OMe)-fluoromethylketone (Z-YVAD-FMK), and a combination of both on atherosclerosis in ApoE-/- mice fed a western diet at 5 weeks of age, and further determined the efficacy of these polypeptide inhibitors in bone marrow-derived macrophages (BMDMs). In vivo studies there was plaque formation, GSDMD activation, and caspase-1 activation in aortas, which increased gradually from 6 to 18 weeks of age, and increased markedly at 14 and 18 weeks of age. ApoE-/- mice were administered Z-LLSD-FMK (200 µg/day), Z-YVAD-FMK (200 µg/day), a combination of both, or vehicle control intraperitoneally from 14 to 18 weeks of age. Treatment significantly reduced lesion formation, macrophage infiltration in lesions, protein levels of vascular cell adhesion molecule-1 and monocyte chemoattractant protein-1, and pyroptosis-related proteins such as activated caspase-1, activated GSDMD, cleaved interleukin(IL)-1β, and high mobility group box 1 in aortas. No overt differences in plasma lipid contents were detected. In vitro treatment with these polypeptide inhibitors dramatically decreased the percentage of propidium iodide-positive BMDMs, the release of lactate dehydrogenase and IL-1β, and protein levels of pyroptosis-related proteins both in supernatants and cell lysates elevated by lipopolysaccharide + nigericin. Notably however, there were no significant differences in the above-mentioned results between the Z-LLSD-FMK group and the Z-YVAD-FMK group, and the combination of both did not yield enhanced effects. These findings indicate that suppression of GSDMD activation by Z-LLSD-FMK or Z-YVAD-FMK reduces vascular inflammation and lesion development in ApoE-/- mice.

Virulence-related gene wx2 of Toxoplasma gondii regulated host immune response via classic pyroptosis pathway

BACKGROUND

Toxoplasma gondii is known as the most successful parasite, which can regulate the host immune response through a variety of ways to achieve immune escape. We previously reported that a novel gene wx2 of T. gondii may be a virulence-related molecule. The objective of this study was to explore the mechanism of wx2 regulating host immune response.

METHODS

The wx2 knockout strain (RH^wx2-/- strain) and complementary strain (RH^wx2+/+ strain) were constructed by the CRISPR/Cas9 technique, and the virulence of the wx2 gene was detected and changes in pyroptosis-related molecules were observed.

RESULTS

Compared with the wild RH and RH^wx2+/+ strain groups, the survival time for mice infected with the RH^wx2-/- strain was prolonged to a certain extent. The mRNA levels of pyroptosis-related molecules of caspase-1, NLRP3, and GSDMD and et al. in mouse lymphocytes in vivo and RAW267.4 cells in vitro infected with RH^wx2-/- strain increased to different degrees, compared with infected with wild RH strain and RH^wx2+/+ strain. As with the mRNA level, the protein level of caspase-1, caspase-1 p20, IL-1β, NLRP3, GSDMD-FL, GSDMD-N, and phosphorylation level of NF-κB (p65) were also significantly increased. These data suggest that wx2 may regulate the host immune response through the pyroptosis pathway. In infected RAW264.7 cells at 48 h post-infection, the levels of Th1-type cytokines of IFN-γ, Th2-type cytokines such as IL-13, Th17-type cytokine of IL-17 in cells infected with RH^wx2-/- were significantly higher than those of RH and RH^wx2+/+ strains, suggesting that the wx2 may inhibit the host's immune response.

CONCLUSION

wx2 is a virulence related gene of T. gondii, and may be involved in host immune regulation by inhibiting the pyroptosis pathway.

Perkinsus marinus suppresses in vitro eastern oyster apoptosis via IAP-dependent and caspase-independent pathways involving TNFR, NF-kB, and oxidative pathway crosstalk

The protozoan parasite Perkinsus marinus causes Dermo disease in eastern oysters, Crassostrea virginica, and can suppress apoptosis of infected hemocytes using incompletely understood mechanisms. This study challenged hemocytes in vitro with P. marinus for 1 h in the presence or absence of caspase inhibitor Z-VAD-FMK or Inhibitor of Apoptosis protein (IAP) inhibitor GDC-0152. Hemocytes exposure to P. marinus significantly reduced granulocyte apoptosis, and pre-incubation with Z-VAD-FMK did not affect P. marinus-induced apoptosis suppression. Hemocyte pre-incubation with GDC-0152 prior to P. marinus challenge further reduced apoptosis of granulocytes with engulfed parasite, but not mitochondrial permeabilization. This suggests P. marinus-induced apoptosis suppression may be caspase-independent, affect an IAP-involved pathway, and occur downstream of mitochondrial permeabilization. P. marinus challenge stimulated hemocyte differential expression of oxidation-reduction, TNFR, and NF-kB pathways. WGCNA analysis of P. marinus expression in response to hemocyte exposure revealed correlated protease, kinase, and hydrolase expression that could contribute to P. marinus-induced apoptosis suppression.

Enhancement of Cancer-Cell-Selective Cytotoxicity by a Dicopper Complex with Phenanthrene Amide-Tether Ligand Conjugate via Mitochondrial Apoptosis

Dicopper complexes [Cu2(μ-OH)(Ln)](ClO4)2 [n = 1 (1) and 2 (2)] with a novel phenanthrene amide-tether ligand conjugate (HL1) and the original p-cresol-2,6-bis(amidecyclen) (HL2) were synthesized. A phenanthrene unit of 1...

Recent contributions of quinolines to antimalarial and anticancer drug discovery research

Quinoline, a privileged scaffold in medicinal chemistry, has always been associated with a multitude of biological activities. Especially in antimalarial and anticancer research, quinoline played (and still plays) a central role, giving rise to the development of an array of quinoline-containing pharmaceuticals in these therapeutic areas. However, both diseases still affect millions of people every year, pointing to the necessity of new therapies. Quinolines have a long-standing history as antimalarial agents, but established quinoline-containing antimalarial drugs are now facing widespread resistance of the Plasmodium parasite. Nevertheless, as evidenced by a massive number of recent literature contributions, they are still of great value for future developments in this field. On the other hand, the number of currently approved anticancer drugs containing a quinoline scaffold are limited, but a strong increase and interest in quinoline compounds as potential anticancer agents can be seen in the last few years. In this review, a literature overview of recent contributions made by quinoline-containing compounds as potent antimalarial or anticancer agents is provided, covering publications between 2018 and 2020.

Pathway network of pyroptosis and its potential inhibitors in acute kidney injury

Acute kidney injury (AKI) is a worldwide problem, and there is no effective drug to eliminate AKI. The death of renal cells is an important pathological basis of intrinsic AKI. At present, targeted therapy for TEC death is a research hotspot in AKI therapy. There are many ways of cell death involved in the occurrence and development of AKI, such as apoptosis, necrosis, ferroptosis, and pyroptosis. This article mainly focuses on the role of pyroptosis in AKI. The assembly and activation of NLRP3 inflammasome is a key event in the occurrence of pyroptosis, which is affected by many factors, such as the activation of the NF-κB signaling pathway, mitochondrial instability and excessive endoplasmic reticulum (ER) stress. The activation of NLRP3 inflammasome can trigger its downstream inflammatory cytokines, which will lead to pyroptosis and eventually induce AKI. In this paper, we reviewed the possible mechanism of pyroptosis in AKI and the potential effective inhibitors of various key targets in this process. It may provide potential therapeutic targets for novel intrinsic AKI therapies based on pyroptosis, so as to develop better therapeutic strategies.

Review of cancer cell resistance mechanisms to apoptosis and actual targeted therapies

The apoptosis pathway is a programmed cell death mechanism that is crucial for cellular and tissue homeostasis and organ development. There are three major caspase-dependent pathways of apoptosis that ultimately lead to DNA fragmentation. Cancerous cells are known to highly regulate the apoptotic pathway and its role in cancer hallmark acquisition has been discussed over the past decades. Numerous mutations in cancer cell types have been reported to be implicated in chemoresistance and treatment outcome. In this review, we summarize the mutations of the caspase-dependant apoptotic pathways that are the source of cancer development and the targeted therapies currently available or in trial.

A long way to go: caspase inhibitors in clinical use

Caspases are an evolutionary conserved family of cysteine-dependent proteases that are involved in many vital cellular processes including apoptosis, proliferation, differentiation and inflammatory response. Dysregulation of caspase-mediated apoptosis and inflammation has been linked to the pathogenesis of various diseases such as inflammatory diseases, neurological disorders, metabolic diseases, and cancer. Multiple caspase inhibitors have been designed and synthesized as a potential therapeutic tool for the treatment of cell death-related pathologies. However, only a few have progressed to clinical trials because of the consistent challenges faced amongst the different types of caspase inhibitors used for the treatment of the various pathologies, namely an inadequate efficacy, poor target specificity, or adverse side effects. Importantly, a large proportion of this failure lies in the lack of understanding various caspase functions. To overcome the current challenges, further studies on understanding caspase function in a disease model is a fundamental requirement to effectively develop their inhibitors as a treatment for the different pathologies. Therefore, the present review focuses on the descriptive properties and characteristics of caspase inhibitors known to date, and their therapeutic application in animal and clinical studies. In addition, a brief discussion on the achievements, and current challenges faced, are presented in support to providing more perspectives for further development of successful therapeutic caspase inhibitors for various diseases.

Coffee Leaves: An Upcoming Novel Food?

Unlike those of coffee beans, the healthy properties of coffee leaves have been overlooked for a long time, even if they are consumed as a beverage by local communities of several African countries. Due to the presence of xanthines, diterpenes, xanthones, and several other polyphenol derivatives as main secondary metabolites, coffee leaves might be useful to prevent many daily disorders. At the same time, as for all bioactive molecules, careless use of coffee leaf infusions may be unsafe due to their adverse effects, such as the excessive stimulant effects on the central nervous system or their interactions with other concomitantly administered drugs. Moreover, the presence of some toxic diterpene derivatives requires careful analytical controls on manufactured products made with coffee leaves. Accordingly, knowledge about the properties of coffee leaves needs to be increased to know if they might be considered a good source for producing new supplements. The purpose of the present review is to highlight the biosynthesis, metabolism, and distribution of the 4 main classes of secondary metabolites present in coffee leaves, their main pharmacological and toxicological aspects, and their main roles in planta. Differences in coffee leaf chemical composition depending on the coffee species will also be carefully considered.

Gasdermin D in pyroptosis

Pyroptosis is the process of inflammatory cell death. The primary function of pyroptosis is to induce strong inflammatory responses that defend the host against microbe infection. Excessive pyroptosis, however, leads to several inflammatory diseases, including sepsis and autoimmune disorders. Pyroptosis can be canonical or noncanonical. Upon microbe infection, the canonical pathway responds to pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs), while the noncanonical pathway responds to intracellular lipopolysaccharides (LPS) of Gram-negative bacteria. The last step of pyroptosis requires the cleavage of gasdermin D (GsdmD) at D275 (numbering after human GSDMD) into N- and C-termini by caspase 1 in the canonical pathway and caspase 4/5/11 (caspase 4/5 in humans, caspase 11 in mice) in the noncanonical pathway. Upon cleavage, the N-terminus of GsdmD (GsdmD-N) forms a transmembrane pore that releases cytokines such as IL-1β and IL-18 and disturbs the regulation of ions and water, eventually resulting in strong inflammation and cell death. Since GsdmD is the effector of pyroptosis, promising inhibitors of GsdmD have been developed for inflammatory diseases. This review will focus on the roles of GsdmD during pyroptosis and in diseases.

IL-17C in human mucosal immunity: More than just a middle child

Interleukin-17C (IL-17C) is an understudied member of the IL-17 family of cytokines. Its synthesis is induced by both cytokines and pathogenic stimuli in a variety of cell types, most often expressed at mucosal and barrier surfaces. IL-17C expression is dysregulated in a variety of autoinflammatory and autoimmune diseases including inflammatory bowel disease, psoriasis, and atopic dermatitis, yet it is protective against bacterial infections of the gut, skin, and lungs. In this review we highlight studies on IL-17C regulation and its function at human mucosal surfaces. Understanding the relationship between IL-17C and autoinflammatory and autoimmune diseases of the mucosa and defining the beneficial and pathogenic functions of the cytokine in inflammatory responses are the first steps in determining the potential for IL-17C as a therapeutic target.

Molecular Imaging of Apoptosis: The Case of Caspase-3 Radiotracers

The molecular imaging of apoptosis remains an important method for the diagnosis and monitoring of the progression of certain diseases and the evaluation of the efficacy of anticancer apoptosis-inducing therapies. Among the multiple biomarkers involved in apoptosis, activated caspase-3 is an attractive target, as it is the most abundant of the executioner caspases. Nuclear imaging is a good candidate, as it combines a high depth of tissue penetration and high sensitivity, features necessary to detect small changes in levels of apoptosis. However, designing a caspase-3 radiotracer comes with challenges, such as selectivity, cell permeability and transient caspase-3 activation. In this review, we discuss the different caspase-3 radiotracers for the imaging of apoptosis together with the challenges of the translation of various apoptosis-imaging strategies in clinical trials.

Serine protease inhibitors of the whirling disease parasite Myxobolus cerebralis (Cnidaria, Myxozoa): Expression profiling and functional predictions

Here, we studied the expression pattern and putative function of four, previously identified serine protease inhibitors (serpins) of Myxobolus cerebralis, a pathogenic myxozoan species (Cnidaria: Myxozoa) causing whirling disease of salmonid fishes. The relative expression profiles of serpins were determined at different developmental stages both in fish and in annelid hosts using serpin-specific qPCR assays. The expression of serpin Mc-S1 was similar throughout the life cycle, whereas a significant decrease was detected in the relative expression of Mc-S3 and Mc-S5 during the development in fish, and then in the sporogonic stage in the worm host. A decreasing tendency could also be observed in the expression of Mc-S4 in fish, which was, however, upregulated in the worm host. For the first time, we predicted the function of M. cerebralis serpins by the use of several bioinformatics-based applications. Mc-S1 is putatively a chymotrypsin-like inhibitor that locates extracellularly and is capable of heparin binding. The other three serpins are caspase-like inhibitors, and they are probably involved in protease and cell degradation processes during the early stage of fish invasion.

Gasdermin E-derived caspase-3 inhibitors effectively protect mice from acute hepatic failure

Programmed cell death (PCD), including apoptosis, apoptotic necrosis, and pyroptosis, is involved in various organ dysfunction syndromes. Recent studies have revealed that a substrate of caspase-3, gasdermin E (GSDME), functions as an effector for pyroptosis; however, few inhibitors have been reported to prevent pyroptosis mediated by GSDME. Here, we developed a class of GSDME-derived inhibitors containing the core structure of DMPD or DMLD. Ac-DMPD-CMK and Ac-DMLD-CMK could directly bind to the catalytic domains of caspase-3 and specifically inhibit caspase-3 activity, exhibiting a lower IC50 than that of Z-DEVD-FMK. Functionally, Ac-DMPD/DMLD-CMK substantially inhibited both GSDME and PARP cleavage by caspase-3, preventing apoptotic and pyroptotic events in hepatocytes and macrophages. Furthermore, in a mouse model of bile duct ligation that mimics intrahepatic cholestasis-related acute hepatic failure, Ac-DMPD/DMLD-CMK significantly alleviated liver injury. Together, this study not only identified two specific inhibitors of caspase-3 for investigating PCD but also, more importantly, shed light on novel lead compounds for treating liver failure and organ dysfunctions caused by PCD.

Poxviral Strategies to Overcome Host Cell Apoptosis

Apoptosis is a form of cellular suicide initiated either via extracellular (extrinsic apoptosis) or intracellular (intrinsic apoptosis) cues. This form of programmed cell death plays a crucial role in development and tissue homeostasis in multicellular organisms and its dysregulation is an underlying cause for many diseases. Intrinsic apoptosis is regulated by members of the evolutionarily conserved B-cell lymphoma-2 (Bcl-2) family, a family that consists of pro- and anti-apoptotic members. Bcl-2 genes have also been assimilated by numerous viruses including pox viruses, in particular the sub-family of chordopoxviridae, a group of viruses known to infect almost all vertebrates. The viral Bcl-2 proteins are virulence factors and aid the evasion of host immune defenses by mimicking the activity of their cellular counterparts. Viral Bcl-2 genes have proved essential for the survival of virus infected cells and structural studies have shown that though they often share very little sequence identity with their cellular counterparts, they have near-identical 3D structures. However, their mechanisms of action are varied. In this review, we examine the structural biology, molecular interactions, and detailed mechanism of action of poxvirus encoded apoptosis inhibitors and how they impact on host–virus interactions to ultimately enable successful infection and propagation of viral infections.

One-Pot Radiosynthesis and Biological Evaluation of a Caspase-3 Selective 5-[123,125I]iodo-1,2,3-triazole derived Isatin SPECT Tracer

Induction of apoptosis is often necessary for successful cancer therapy, and the non-invasive monitoring of apoptosis post-therapy could assist in clinical decision making. Isatins are a class of compounds that target activated caspase-3 during apoptosis. Here we report the synthesis of the 5-iodo-1,2,3-triazole (FITI) analog of the PET tracer [18F]ICMT11 as a candidate tracer for imaging of apoptosis with SPECT, as well as PET. Labelling with radioiodine (123,125I) was achieved in 55 ± 12% radiochemical yield through a chelator-accelerated one-pot cycloaddition reaction mediated by copper(I) catalysis. The caspase-3 binding affinity and selectivity of FITI compares favourably to that of [18F]ICMT11 (Ki = 6.1 ± 0.9 nM and 12.4 ± 4.7 nM, respectively). In biodistribution studies, etoposide-induced cell death in a SW1222 xenograft model resulted in a 2-fold increase in tumour uptake of the tracer. However, the tumour uptake was too low to allow in vivo imaging of apoptosis with SPECT.

PFKFB3 Inhibition Attenuates Oxaliplatin-Induced Autophagy and Enhances Its Cytotoxicity in Colon Cancer Cells

6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase isoform 3 (PFKFB3), a glycolytic enzyme highly expressed in cancer cells, has been reported to participate in regulating metabolism, angiogenesis, and autophagy. Although anti-cancer drug oxaliplatin (Oxa) effectively inhibits cell proliferation and induces apoptosis, the growing resistance and side-effects make it urgent to improve the therapeutic strategy of Oxa. Although Oxa induces the autophagy process, the role of PFKFB3 in this process remains unknown. In addition, whether PFKFB3 affects the cytotoxicity of Oxa has not been investigated. Here, we show that Oxa-inhibited cell proliferation and migration concomitant with the induction of apoptosis and autophagy in SW480 cells. Both inhibition of autophagy by small molecule inhibitors and siRNA modification decreased the cell viability loss and apoptosis induced by Oxa. Utilizing quantitative PCR and immunoblotting, we observed that Oxa increased PFKFB3 expression in a time- and dose-dependent manner. Meanwhile, suppression of PFKFB3 attenuated both the basal and Oxa-induced autophagy, by monitoring the autophagic flux and phosphorylated-Ulk1, which play essential roles in autophagy initiation. Moreover, PFKFB3 inhibition further inhibited the cell proliferation/migration, and cell viability decreased by Oxa. Collectively, the presented data demonstrated that PFKFB3 inhibition attenuated Oxa-induced autophagy and enhanced its cytotoxicity in colorectal cancer cells.

From the Explored to the Unexplored: Computer-Tailored Drug Design Attempts in the Discovery of Selective Caspase Inhibitors

The pathophysiological roles of caspases have made them attractive targets in the treatment and amelioration of neurologic diseases. In normal conditions, the expression of caspases is regulated in the brain, while at the onset of neurodegeneration, such as in Alzheimer's disease, they are typically overexpressed. Till date, several therapeutic efforts that include the use of small endogenous binders have been put forward to curtail dysfunctionalities that drive aberrant death in neuronal cells. Caspases are highly homologous, both in structure and in sequence, which leaves us with the question: is it possible to specifically and individually target caspases, while multiple therapeutic attempts to achieve selective targeting have failed! Based on antecedent events, the use of Computer-Aided Drug Design (CADD) methods has significantly contributed to the design of small molecule inhibitors, especially with selective target ability and reduced off-target therapeutic effects. Interestingly, we found out that there still exists an enormous room for the integration of structure/ligand-based drug design techniques towards the development of highly specific reversible and irreversible caspase inhibitors. Therefore, in this review, we highlight drug discovery approaches that have been directed towards caspase inhibition in addition to an insightful focus on applicable CADD techniques for achieving selective targeting in caspase research.

Novel association between apoptotic sperm biomarkers with seminal biochemical parameters and acetylcholinesterase activity in patients with teratozoospermia

OBJECTIVE

We aimed to determine whether the dysfunction of physiological apoptosis and specific seminal biochemical parameters could be associated with male infertility and sperm morphological defects.

STUDY DESIGN

Ejaculated sperm samples from sixty patients with isolated teratozoospermia and thirty fertile donors were analyzed. The proportion of both viable and dead spermatozoa expressing activated caspases was detected by fluorescence microscopy through the use of different specific carboxyfluorescein-labeled caspase inhibitors FLICA. The different stages of apoptosis in human were qualitatively and quantitatively determined by using the AO/EB fluorescent staining method. The levels of the seminal biochemical parameters (acetylcholinesterase (AChE), lactate dehydrogenase (LDH), creatine phosphokinase (CK), iron (Fe), calcium (Ca), and phosphorus (P)) were evaluated spectrophotometrically.

RESULTS

Patients with teratozoospermia showed significantly higher proportions of dead and live spermatozoa with activated caspases and spermatozoa in the late stage of apoptosis when compared to controls. Among the different studied biochemical seminal parameters, the rates of acetylcholinesterase activity, creatine phosphokinase, iron, and calcium were significantly increased in the patient group. However, the rate of phosphorus was significantly decreased. Interestingly, significant relationships were found between the studied biochemical and apoptotic biomarkers and the rates of atypical sperm forms with the incidences of head, mid-piece, and tail abnormalities. Furthermore, positive correlations were found between P, AChE, Fe, CK, and LDH with apoptotic markers.

CONCLUSIONS

These results emphasize the impact of apoptosis in the pathophysiology of teratozoospermia and suggest that seminal biochemical disturbance may arise such damage.

Circular zymogens of human ribonuclease 1

The endogenous production of enzymes as zymogens provides a means to control catalytic activities. Here, we describe the heterologous production of ribonuclease 1 (RNase 1), which is the most prevalent secretory ribonuclease in humans, as a zymogen. In folded RNase 1, the N and C termini flank the enzymic active site. By using intein-mediated cis-splicing, we created circular proteins in which access to the active site of RNase 1 is obstructed by an amino-acid sequence that is recognized by the HIV-1 protease. Installing a sequence that does not perturb the RNase 1 fold led to only modest inactivation. In contrast, the ancillary truncation of residues from each terminus led to a substantial decrease in the catalytic activity of the zymogen with the maintenance of thermostability. For optimized zymogens, activation by HIV-1 protease led to a > 104 -fold increase in ribonucleolytic activity at a rate comparable to that for the cleavage of endogenous viral substrates. Molecular modeling indicated that these zymogens are inactivated by conformational distortion in addition to substrate occlusion. Because protease levels are elevated in many disease states and ribonucleolytic activity can be cytotoxic, RNase 1 zymogens have potential as generalizable prodrugs.

The protective effects of the antioxidant N-acetylcysteine (NAC) against oxidative stress-associated apoptosis evoked by the organophosphorus insecticide malathion in normal human astrocytes

Malathion is one of the most widely used organophosphorus insecticides in agriculture. However, malathion may be involved in the etiology of human brain dysfunction. Induction of ROS has been proposed as a mechanism of malathion-induced poisoning cases, but there are few data regarding the effects of malathion on oxidative stress-associated neurotoxicity in human glial cells. The aim was to explore the mechanism underlying effects of malathion on neurotoxicity in Gibco^® Human Astrocytes (GHA cells) and evaluate the protective effects of the antioxidant (N-acetylcysteine, NAC). Cell viability was measured by the cell proliferation reagent (WST-1). Antioxidant enzymes (glutathione peroxidase and catalase) were measured by an ELISA reader. Cell cycle distribution and ROS productions were detected by flow cytometry. Cell cycle-related protein levels (cyclin E1, CDK2, cyclin A2, CDK1/CDC2, or cyclin B1) and apoptotic protein levels (Bcl-2, Bax, and cleaved caspase-9/caspase-3) were analyzed by Western blotting. In GHA cells, treatment with malathion (10-25 μM) for 24 h concentration-dependently induced cytotoxicity and cell cycle arrest. In terms of oxidative stresses, malathion elevated intracellular ROS levels, but reduced glutathion and antioxidant enzyme levels. Treatment with NAC (5 μM) reversed malathion-induced oxidative stress responses, and prevented malathion-evoked apoptosis by regulating apoptotic protein expressions. Together, in GHA cells, NAC mediated inhibition of malathion-activated mitochondrial apoptotic pathways that involved cell cycle arrest and ROS responses. These data provide further insights into the molecular mechanisms behind malathion poisoning, and might suggest that NAC with its protective effects may be a potential compound for prevention of malathion-induced brain injury.

Techniques for the Study of Apoptosis in Bone

Osteocyte apoptosis has been associated with a number of clinical conditions in bone and with the targeted turnover of specific skeletal areas. There has been great interest in the identification of the mechanisms by which apoptosis is regulated in bone and in the biological role that this process plays in bone metabolism and associated bone disease or loss of structural integrity. Here we describe several methods for the detection of apoptosis in bone sections and in bone cell cultures.

LT-IIc, A Bacterial Type II Heat-Labile Enterotoxin, Induces Specific Lethality in Triple Negative Breast Cancer Cells by Modulation of Autophagy and Induction of Apoptosis and Necroptosis

Triple negative breast cancer (TNBC) remains a serious health problem with poor prognosis and limited therapeutic options. To discover novel approaches to treat TNBC, we screened cholera toxin (CT) and the members of the bacterial type II heat-labile enterotoxin family (LT-IIa, LT-IIb, and LT-IIc) for cytotoxicity in TNBC cells. Only LT-IIc significantly reduced viability of the TNBC cell lines BT549 and MDA-MB-231 (IC₅₀ = 82.32 nM). LT-IIc had no significant cytotoxic effect on MCF10A (IC₅₀ = 2600 nM), a non-tumorigenic breast epithelial cell line, and minimal effects on MCF7 and T47D, ER⁺ cells, or SKBR-3 cells, HER2⁺ cells. LT-IIc stimulated autophagy through inhibition of the mTOR pathway, while simultaneously inhibiting autophagic progression, as seen by accumulation of LC3B-II and p62. Morphologically, LT-IIc induced the formation of enlarged LAMP2+ autolysosomes, which was blocked by co-treatment with bafilomycin A1. LT-IIc induced apoptosis as demonstrated by the increase in caspase 3/7 activity and Annexin V staining. Co-treatment with necrostatin-1, however, demonstrated that the lethal response of LT-IIc is elicited, in part, by concomitant induction of necroptosis. Knockdown of ATG-5 failed to rescue LT-IIc-induced cytotoxicity, suggesting LT-IIc can exert its cytotoxic effects downstream or independently of autophagophore initiation. Collectively, these experiments demonstrate that LT-IIc acts bifunctionally, inducing autophagy, while simultaneously blocking autolysosomal progression in TNBC cells, inducing a specific cytotoxicity in this breast cancer subtype.

Mechanism of gasdermin D recognition by inflammatory caspases and their inhibition by a gasdermin D-derived peptide inhibitor

The inflammasomes are signaling platforms that promote the activation of inflammatory caspases such as caspases-1, -4, -5, and -11. Recent studies identified gasdermin D (GSDMD) as an effector for pyroptosis downstream of the inflammasome signaling pathways. Cleavage of GSDMD by inflammatory caspases allows its N-terminal domain to associate with membrane lipids and form pores that induce pyroptotic cell death. Despite the important role of GSDMD in pyroptosis, the molecular mechanisms of GSDMD recognition and cleavage by inflammatory caspases that trigger pyroptosis are poorly understood. Here, we demonstrate that the catalytic domains of inflammatory caspases can directly bind to both the full-length GSDMD and its cleavage site peptide, FLTD. A GSDMD-derived inhibitor, N-acetyl-Phe-Leu-Thr-Asp-chloromethylketone (Ac-FLTD-CMK), inhibits GSDMD cleavage by caspases-1, -4, -5, and -11 in vitro, suppresses pyroptosis downstream of both canonical and noncanonical inflammasomes, as well as reduces IL-1β release following activation of the NLRP3 inflammasome in macrophages. By contrast, the inhibitor does not target caspase-3 or apoptotic cell death, suggesting that Ac-FLTD-CMK is a specific inhibitor for inflammatory caspases. Crystal structure of caspase-1 in complex with Ac-FLTD-CMK reveals extensive enzyme-inhibitor interactions involving both hydrogen bonds and hydrophobic contacts. Comparison with other caspase-1 structures demonstrates drastic conformational changes at the four active-site loops that assemble the catalytic groove. The present study not only contributes to our understanding of GSDMD recognition by inflammatory caspases but also reports a specific inhibitor for these caspases that can serve as a tool for investigating inflammasome signaling.

Induction of ultra-morphological features of apoptosis in mature and immature sperm

There is a fundamental body of evidence suggesting that activated apoptosis signaling in ejaculated human sperm negatively influences their fertilization potential. However, it is still controversial whether this apoptotic signaling is a relic of an abortive apoptosis related to spermatogenesis or if it should be regarded as a functional preformed pathway in mature sperm leading to stereotypical morphological changes reflecting nuclear disassembly. To address this question, apoptosis was induced using betulinic acid in mature and immature ejaculated human sperm enriched by density gradient centrifugation. Execution of apoptosis was monitored by observing ultra-morphological changes via transmission electron microscopy. Typical morphological signs of apoptosis in somatic cells include plasma membrane blebbing with the formation of apoptotic bodies, impaired mitochondrial integrity, defects of the nuclear envelope, and nuclear fragmentation; these morphologies have also been observed in human sperm. In addition, these apoptotic characteristics were more frequent in immature sperm compared to mature sperm. Following betulinic acid treatment, apoptosis-related morphological changes were induced in mature sperm from healthy donors. This effect was much less pronounced in immature sperm. Moreover, in both fractions, the betulinic acid treatment increased the percentage of acrosome-reacted sperm. The results of our ultra-morphological study prove the functional competence of apoptosis in mature ejaculated human sperm. The theory of a sole abortive process may be valid only for immature sperm. The induction of the acrosome reaction by stimulating apoptosis might shed light on the biological relevance of sperm apoptosis.

Bile acids at neutral and acidic pH induce apoptosis and gene cleavages in nasopharyngeal epithelial cells: implications in chromosome rearrangement

BACKGROUND

Chronic rhinosinusitis (CRS) increases the risk of developing nasopharyngeal carcinoma (NPC) while nasopharyngeal reflux is known to be one of the major aetiological factors of CRS. Bile acid (BA), the component of gastric duodenal contents, has been recognised as a carcinogen. BA-induced apoptosis was suggested to be involved in human malignancies. Cells have the potential and tendency to survive apoptosis. However, cells that evade apoptosis upon erroneous DNA repair may carry chromosome rearrangements. Apoptotic nuclease, caspase-activated deoxyribonuclease (CAD) has been implicated in mediating translocation in leukaemia. We hypothesised that BA-induced apoptosis may cause chromosome breaks mediated by CAD leading to chromosome rearrangement in NPC. This study targeted the AF9 gene located at 9p22 because 9p22 is one of the most common deletion sites in NPC.

METHODS

We tested the ability of BA at neutral and acidic pH in inducing phosphatidylserine (PS) externalisation, reactive oxygen species (ROS) production, mitochondrial membrane potential (MMP) disruption, and caspase 3/7 activity in normal nasopharyngeal epithelial (NP69) and NPC (TWO4) cells. Inverse-PCR (IPCR) was employed to detect AF9 gene cleavages. To investigate the role of CAD in mediating these cleavages, caspase inhibition was performed. IPCR bands representing AF9 cleaved fragments were sequenced.

RESULTS

BA-treated cells showed higher levels of PS externalisation, ROS production, MMP loss and caspase 3/7 activity than untreated control cells. The effect of BA in the induction of these intracellular events was enhanced by acid. BA at neutral and acidic pH also induced significant cleavage of the AF9 gene. These BA-induced gene cleavages were inhibited by Z-DEVD-FMK, a caspase-3 inhibitor. Intriguingly, a few chromosome breaks were identified within the AF9 region that was previously reported to participate in reciprocal translocation between the mixed lineage leukaemia (MLL) and AF9 genes in an acute lymphoblastic leukaemia (ALL) patient.

CONCLUSIONS

These findings suggest a role for BA-induced apoptosis in mediating chromosome rearrangements in NPC. In addition, CAD may be a key player in chromosome cleavages mediated by BA-induced apoptosis. Persistent exposure of sinonasal tract to gastric duodenal refluxate may increase genomic instability in surviving cells.

ER stress-mediated autophagic cell death induction through methylated β-cyclodextrins-threaded acid-labile polyrotaxanes

Autophagy plays a pivotal role in the development and prevention of numerous diseases, and the induction of autophagy is regarded as a potential therapeutic approach for intractable diseases. In this study, the induction of autophagy by methylated β-cyclodextrins (Me-β-CDs)-threaded acid-labile polyrotaxane (Me-PRX) that can release the threaded Me-β-CDs in response to acidic pH in lysosomes was investigated. We hypothesized that the Me-β-CDs released from the Me-PRX interact with the membrane of organelles and cause autophagy. The Me-PRX preferentially accumulated in endoplasmic reticulum (ER) and caused ER stress, which was confirmed by gene expression analysis and the expression of an ER stress-marker protein. Accompanying the ER stress, cells treated with Me-PRX showed autophagy, which was not observed in cells treated with non-labile Me-PRX, other chemically modified PRXs, or free Me-β-CD. Furthermore, the Me-PRX treatment induced autophagic cell death and caused cell death even in apoptosis-resistant cells. Overall, this study demonstrates that the acid-labile Me-PRX induces ER stress-mediated autophagic cell death, and the Me-PRX would be a promising candidate to induce effective cell death in apoptosis-resistant malignant tumors.

Immunohistochemical expression of X-linked inhibitor of apoptosis in eyelid sebaceous gland carcinoma predicts a worse prognosis

Purpose:

Overexpression of the inhibitors of apoptosis proteins have been demonstrated in a variety and of solid tumors including melanomas and nonmelanomas skin cancers. X-linked inhibitor of apoptosis protein (XIAP) is an inhibitor of apoptosis which prevents apoptosis by inhibiting caspases 9, 7, and 3. The prognostic value of XIAP in sebaceous gland carcinoma (SGC) remains unexplored.

Methods:

The immunohistochemical expression of XIAP was evaluated in 29 SGC cases.

Results:

The cytoplasmic overexpression of XIAP was detected in 62% SGC cases. XIAP expression was found to be significantly associated with advanced age, large tumor size, and with reduced disease-free survival (P = 0.0174). XIAP expression and advance tumor Grade III emerged as significant risk factors on univariate analysis. On stepwise multivariate analysis, both increased cytoplasmic XIAP expression and high tumor grade were found to be significantly associated with recurrence. Patients with low XIAP immunoexpression had a longer disease-specific survival than those with high expression in the 5-year follow-up.

Conclusion:

The present study demonstrates at the immunohistochemical level that XIAP is overexpressed in SGC and that high expression could be of biological significance in the development of eyelid SGC. Our finding suggests that up-regulation of XIAP may aggravate tumor metastasis in SGC.

Evaluation of cytotoxicity of propofol and its related mechanism in glioblastoma cells and astrocytes

Propofol (2,6-diisopropylphenol), one of the extensively and commonly used anesthetic agents, has been shown to affect the biological behavior of various models. Previous researches have shown that propofol-induced cytotoxicity might cause anticancer effect in different cells. However, the mechanisms underlying the effect of propofol on cytotoxicity is still elusive in human glioblastoma cells. The aims of this study were to evaluate effects of propofol on cytotoxicity, cell cycle distribution and ROS production, and establish the relationship between oxidative stress and cytotoxicity in GBM 8401 human glioblastoma cells and DI TNC1 rat astrocytes. Propofol (20-30 μM) concentration-dependently induced cytotoxicity, cell cycle arrest, and increased ROS production in GBM 8401 cells but not in DI TNC1 cells. In GBM 8401 cells, propofol induced G2/M phase cell arrest, which affected the CDK1, cyclin B1, p53, and p21 protein expression levels. Furthermore, propofol induced oxygen stresses by increasing O2- and H₂ O₂ levels but treatment with the antioxidant N-acetylcysteine (NAC) partially reversed propofol-regulated antioxidative enzyme levels (superoxide dismutase, catalase, and glutathione peroxidase). Most significantly, propofol induced apoptotic effects by decreasing Bcl-2 but increasing Bax, cleaved caspase-9/caspase-3 levels, which were partially reversed by NAC. Moreover, the pancaspase inhibitor Z-VAD-FMK also partially prevented propofol-induced apoptosis. Together, in GBM 8401 cells but not in DI TNC1 cells, propofol activated ROS-associated apoptosis that involved cell cycle arrest and caspase activation. These findings indicate that propofol not only can be an anesthetic agent which reduces pain but also has the potential to be used for the treatment of human glioblastoma.

Caspase-3/-7-Specific Metabolic Precursor for Bioorthogonal Tracking of Tumor Apoptosis

Apoptosis is one of the most important intracellular events in living cell, which is a programmed cell death interrelated with caspase enzyme activity for maintaining homeostasis in multicellular organisms. Therefore, direct apoptosis imaging of living cells can provide enormous advantages for diagnosis, drug discovery, and therapeutic monitoring in various diseases. However, a method of direct apoptosis imaging has not been fully validated, especially for live cells in in vitro and in vivo. Herein, we developed a new apoptosis imaging technology via a direct visualization of active caspase-3/-7 activity in living cells. For this, we synthesized a caspase-3/-7-specific cleavable peptide (KGDEVD) conjugated triacetylated N-azidoacetyl-D-mannosamine (Apo-S-Ac₃ManNAz), wherein the Apo-S-Ac₃ManNAz can be cleaved by the active caspase-3/-7 in live apoptotic cells and the cleaved Ac₃ManNAz molecules can further generate targetable azido groups (N₃) on the living cell surface. Importantly, the azido groups on the apoptotic tumor cells could be visualized with Cy5.5-conjugated dibenzylcyclooctyne (DBCO-Cy5.5) via bioorthogonal click chemistry in vitro cell culture condition and in vivo tumor-bearing mice. Therefore, our Apo-S-Ac₃ManNAz can be utilized for the further applications in tumor therapy as a monitoring tool for anticancer efficacy and optimization of anticancer new drugs in cell culture system and in tumor-bearing mice.

Nigritoxin is a bacterial toxin for crustaceans and insects

The Tetraconata (Pancrustacea) concept proposes that insects are more closely related to aquatic crustaceans than to terrestrial centipedes or millipedes. The question therefore arises whether insects have kept crustacean-specific genetic traits that could be targeted by specific toxins. Here we show that a toxin (nigritoxin), originally identified in a bacterial pathogen of shrimp, is lethal for organisms within the Tetraconata and non-toxic to other animals. X-ray crystallography reveals that nigritoxin possesses a new protein fold of the α/β type. The nigritoxin N-terminal domain is essential for cellular translocation and likely encodes specificity for Tetraconata. Once internalized by eukaryotic cells, nigritoxin induces apoptotic cell death through structural features that are localized in the C-terminal domain of the protein. We propose that nigritoxin will be an effective means to identify a Tetraconata evolutionarily conserved pathway and speculate that nigritoxin holds promise as an insecticidal protein.

The Tetraconata concept suggests that insects and crustaceans may share evolutionarily conserved pathways. Here, the authors describe the animal tropism and structure-function relationship of nigritoxin, showing that this protein is lethal for insects and crustaceans but harmless to other animals.

Poxviruses Utilize Multiple Strategies to Inhibit Apoptosis

Cells have multiple means to induce apoptosis in response to viral infection. Poxviruses must prevent activation of cellular apoptosis to ensure successful replication. These viruses devote a substantial portion of their genome to immune evasion. Many of these immune evasion products expressed during infection antagonize cellular apoptotic pathways. Poxvirus products target multiple points in both the extrinsic and intrinsic apoptotic pathways, thereby mitigating apoptosis during infection. Interestingly, recent evidence indicates that poxviruses also hijack cellular means of eliminating apoptotic bodies as a means to spread cell to cell through a process called apoptotic mimicry. Poxviruses are the causative agent of many human and veterinary diseases. Further, there is substantial interest in developing these viruses as vectors for a variety of uses including vaccine delivery and as oncolytic viruses to treat certain human cancers. Therefore, an understanding of the molecular mechanisms through which poxviruses regulate the cellular apoptotic pathways remains a top research priority. In this review, we consider anti-apoptotic strategies of poxviruses focusing on three relevant poxvirus genera: Orthopoxvirus, Molluscipoxvirus, and Leporipoxvirus. All three genera express multiple products to inhibit both extrinsic and intrinsic apoptotic pathways with many of these products required for virulence.

Cytotoxic effects of gastrodin extracted from the rhizome of Gastrodia elata Blume in glioblastoma cells, but not in normal astrocytes, via the induction of oxidative stress-associated apoptosis that involved cell cycle arrest and p53 activation

Researches have been conducted to explore the biological effect of gastrodin, a natural compound extracted from the rhizome of Gastrodia elata Blume, in different models. However, the effects of gastrodin on cytotoxicity, cell cycle distribution and oxidative stress in glia cells have not been explored. The aim of this study was to investigate the cytotoxic effect of gastrodin and its mechanisms in DBTRG-05MG human glioblastoma cells and CTX TNA2 rat astrocytes. In DBTRG-05MG cells but not in CTX TNA2 cells, gastrodin (20-30 μM) induced cytotoxicity, G2/M phase cell cycle arrest and apoptosis. Regarding oxidative stress, gastrodin (20-30 μM) elevated intracellular ROS levels but reduced GSH levels. Treatment with the antioxidant NAC (10 μM) partially reversed gastrodin-altered antioxidant enzymes levels. Furthermore, gastrodin induced mitochondria-associated apoptosis. The apoptotic effects evoked by gastrodin were partially inhibited by the antioxidant NAC and the pancaspase inhibitor Z-VAD-FMK. Together, in DBTRG-05MG cells, but not in CTX TNA2 cells, gastrodin activated ROS-associated mitochondrial apoptotic pathways that involved cell cycle arrest. These data provide insight into the molecular mechanisms governing the ability of gastrodin to induce cytotoxicity in human glioblastoma cells and further suggest that gastrodin is a new potential agent for the treatment of human gliblasoma.

Human monocytes downregulate innate response receptors following exposure to the microbial metabolite n-butyrate

Introduction

Hyporesponsiveness of human lamina propria immune cells to microbial and nutritional antigens represents one important feature of intestinal homeostasis. It is at least partially mediated by low expression of the innate response receptors CD11b, CD14, CD16 as well as the cystine‐glutamate transporter xCT on these cells. Milieu‐specific mechanisms leading to the down‐regulation of these receptors on circulating monocytes, the precursor cells of resident macrophages, are mostly unknown.

Methods

Here, we addressed the question whether the short chain fatty acid n‐butyrate, a fermentation product of the mammalian gut microbiota exhibiting histone deacetylase inhibitory activity, is able to modulate expression of these receptors in human circulating monocytes.

Results

Exposure to n‐butyrate resulted in the downregulation of CD11b, CD14, as well as CD16 surface expression on circulating monocytes. XCT transcript levels in circulating monocytes were also reduced following exposure to n‐butyrate. Importantly, treatment resulted in the downregulation of protein and gene expression of the transcription factor PU.1, which was shown to be at least partially required for the expression of CD16 in circulating monocytes. PU.1 expression in resident macrophages in situ was observed to be substantially lower in healthy when compared to inflamed colonic mucosa.

Conclusions

In summary, the intestinal microbiota may support symbiosis with the human host organism by n‐butyrate mediated downregulation of protein and gene expression of innate response receptors as well as xCT on circulating monocytes following recruitment to the lamina propria. Downregulation of CD16 gene expression may at least partially be caused at the transcriptional level by the n‐butyrate mediated decrease in expression of the transcription factor PU.1 in circulating monocytes.

Caspases in retinal ganglion cell death and axon regeneration

Retinal ganglion cells (RGC) are terminally differentiated CNS neurons that possess limited endogenous regenerative capacity after injury and thus RGC death causes permanent visual loss. RGC die by caspase-dependent mechanisms, including apoptosis, during development, after ocular injury and in progressive degenerative diseases of the eye and optic nerve, such as glaucoma, anterior ischemic optic neuropathy, diabetic retinopathy and multiple sclerosis. Inhibition of caspases through genetic or pharmacological approaches can arrest the apoptotic cascade and protect a proportion of RGC. Novel findings have also highlighted a pyroptotic role of inflammatory caspases in RGC death. In this review, we discuss the molecular signalling mechanisms of apoptotic and inflammatory caspase responses in RGC specifically, their involvement in RGC degeneration and explore their potential as therapeutic targets.

Coptisine-induced cell cycle arrest at G2/M phase and reactive oxygen species-dependent mitochondria-mediated apoptosis in non-small-cell lung cancer A549 cells

This study aimed to explore the effect of coptisine on non-small-cell lung cancer and its mechanism through various in vitro cellular models (A549). Results claimed significant inhibition of proliferation by coptisine against A549, H460, and H2170 cells with IC₅₀ values of 18.09, 29.50, and 21.60 µM, respectively. Also, coptisine exhibited upregulation of pH2AX, cell cycle arrest at G2/M phase, and downregulation of the expression of cyclin B1, cdc2, and cdc25C and upregulation of p21 dose dependently. Furthermore, induction of apoptosis in A549 cells by coptisine was characterized by the activation of caspase 9, caspase 8, and caspase 3, and cleavage of poly adenosine diphosphate ribose polymerase. In addition, coptisine was found to increase reactive oxygen species generation, upregulate Bax/Bcl-2 ratio, disrupt mitochondrial membrane potential, and cause cytochrome c release into the cytosol. Besides, treatment with a reactive oxygen species inhibitor (N-acetyl cysteine) abrogated coptisine-induced growth inhibition, apoptosis, reactive oxygen species generation, and mitochondrial dysfunction. Thus, the mediation of reactive oxygen species in the apoptosis-induced effect of coptisine in A549 cells was corroborated. These findings have offered new insights into the effect and mechanisms of action of coptisine against non-small-cell lung cancer.

Vaccinia virus evasion of regulated cell death

Regulated cell death is a powerful anti-viral mechanism capable of aborting the virus replicative cycle and alerting neighbouring cells to the threat of infection. The biological importance of regulated cell death is illustrated by the rich repertoire of host signalling cascades causing cell death and by the multiple strategies exhibited by viruses to block death signal transduction and preserve cell viability. Vaccinia virus (VACV), a poxvirus and the vaccine used to eradicate smallpox, encodes multiple proteins that interfere with apoptotic, necroptotic and pyroptotic signalling. Here the current knowledge on cell death pathways and how VACV proteins interact with them is reviewed. Studying the mechanisms evolved by VACV to counteract host programmed cell death has implications for its successful use as a vector for vaccination and as an oncolytic agent against cancer.

Schiff bases in medicinal chemistry: a patent review (2010-2015)

INTRODUCTION

Schiff bases are synthetically accessible and structurally diverse compounds, typically obtained by facile condensation between an aldehyde, or a ketone with primary amines. Schiff bases contain an azomethine (-C = N-) linkage that stitches together two or more biologically active aromatic/heterocyclic scaffolds to form various molecular hybrids with interesting biological properties. Schiff bases are versatile metal complexing agents and have been known to coordinate all metals to form stable metal complexes with vast therapeutic applications. Areas covered: This review aims to provide a comprehensive overview of the various patented therapeutic applications of Schiff bases and their metal complexes from 2010 to 2015. Expert opinion: Schiff bases are a popular class of compounds with interesting biological properties. Schiff bases are also versatile metal complexing ligands and have been used to coordinate almost all d-block metals as well as lanthanides. Therapeutically, Schiff bases and their metal complexes have been reported to exhibit a wide range of biological activities such as antibacterial including antimycobacterial, antifungal, antiviral, antimalarial, antiinflammatory, antioxidant, pesticidal, cytotoxic, enzyme inhibitory, and anticancer including DNA damage.