Caspase Activation

Decoding the role of HIF-1α in immunoregulation in Litopenaeus vannamei under hypoxic stress

Hypoxia poses a significant challenge to aquatic organisms, especially Litopenaeus vannamei (L. vannamei), which play a vital role in the global aquaculture industry. Hypoxia-inducible factor 1α (HIF-1α) is a pivotal regulator of the organism's adaptation to hypoxic conditions. To understand of how HIF-1α affects the immunity of L. vannamei under hypoxic conditions, we conducted a thorough study involving various approaches. These included observing tissue morphology, analyzing the expression of immune-related genes, assessing the activities of immune-related enzymes, and exploring immune-related pathways. Our study revealed that RNA interference (RNAi)-mediated knockdown of HIF-1α markedly reduced HIF-1α expression in the gill (75-95 %), whereas the reduction ranged from 2 to 43 % in the hepatopancreas. Knockdown of HIF-1α resulted in increased damage to both gill and hepatopancreatic tissues in hypoxic conditions. Additionally, immune-related genes, including Astakine (AST), Hemocyanin (HC), and Ferritin (FT), as well as immune-related enzymes such as Acid Phosphatase (ACP), Alkaline Phosphatase (AKP), and Phenoloxidase (PO), exhibited intricate regulatory patterns in response to hypoxia stress following the knockdown of HIF-1α. Transcriptome analysis revealed that HIF-1α knockdown significantly impacts multiple signaling pathways, including the JAK-STAT signaling pathway, Th17 cell differentiation pathways, PI3K-Akt signaling pathway, ErbB signaling pathway, MAPK signaling pathway, chemokine signaling pathway, ribosomal pathways, apoptosis, lysosomes and arachidonic acid metabolism. These alterations disrupt the organism's immune balance and interfere with normal metabolic processes, potentially leading to various immune-related diseases. We speculate that the weakened immune response resulting from HIF-1 inhibition is due to the reduced metabolic capacity, and the existence of a direct regulatory relationship between them requires further exploration. This study greatly advances our understanding of the vital role that HIF-1α plays in regulating immune responses in shrimp under hypoxic conditions, thereby deepening our comprehension of this critical biological mechanism.

ACOT7 positively regulated by CREB1 promotes the progression of cutaneous melanoma

Cutaneous melanoma (cM) is a prevalent invasive cancer resulting from the malignant transformation of melanocytes. At present, the primary treatment for melanoma is surgical resection, which is not appropriate for patients with metastasis. Therefore, it is necessary to identify effective therapeutic targets for the early diagnosis and treatment of metastatic melanoma. Acyl-CoA thioesterase 7 (ACOT7) has been reported to be involved in the progression of multiple cancer, while its role in melanoma has not been extensively researched. Through gain-of-function and loss-of-function experiments, ACOT7 was identified as a tumor promoter that facilitates the progression of melanoma cells. Cell proliferation was promoted by overexpressing ACOT7 in M14 cells, and was suppressed by silencing ACOT7 in MeWo cells. Knockdown of ACOT7 induced cell cycle arrest by increasing the expressions of cyclin dependent kinase inhibitor 1B (P27) and cyclin dependent kinase inhibitor 1 A (P21), while simultaneously reducing proliferating cell nuclear antigen (PCNA) expression. Upregulation of ACOT7 promoted the cell cycle of melanoma cells. Additionally, apoptosis was induced by the absence of ACOT7 through activating caspase-3 and poly (ADP-ribose) polymerase (PARP). The metastatic and invasive capacity of melanoma cells was significantly enhanced by the overexpression of ACOT7 and inhibited by the downregulation of ACOT7. Moreover, the cAMP responsive element binding protein 1 (CREB1) positively regulates ACOT7 expression by binding to its promoter region. A decrease of cell proliferation, migration and invasion, as well as an increase of cell apoptosis induced by silencing CREB1 were obviously reversed by ACOT7. In summary, ACOT7 transcriptionally activated by CREB1 elevates the progression of cM.

Rotenone and Its Derivative, Rotenoisin A, Induce Neurodegeneration Differentially in SH-SY5Y Cells

Rotenone (ROT), the most significant rotenoid, which has shown anticancer activity, has also been reported to be toxic to normal cells, inducing Parkinson's disease (PD)-like neuronal loss with aggregation of α-synuclein (α-syn). To reduce the adverse effects of ROT, its derivative, rotenoisin A (ROA), is obtained by directly irradiating a ROT solution in methanol using γ-rays, which has been reported for potential anticancer properties. However, its PD-inducing effects have not yet been researched or reported. This study sought to compare the activities of ROA and ROT on the aggregation of α-syn, apoptosis, and autophagy in SH-SY5Y cells. ROA decreased cell survival less when compared with ROT on SH-SY5Y cells at 48 h in a dose-dependent manner. ROT (0.5 and 1 μM) and ROA (4 and 5 μM) decreased the expression of tyrosine hydroxylase. Western blot analysis of the Triton X-100 insoluble fraction revealed that both ROT and ROA significantly increased the levels of oligomeric, dimeric, and monomeric phosphorylated Serine129 α-syn and total monomeric α-syn. Moreover, both compounds decreased the proportion of neuronal nuclei, the neurofilament-heavy chain, and β3-tubulin. The phosphorylation of ERK and SAPK were reduced, whereas ROA did not act on Akt. Additionally, the increased Bax/Bcl-2 ratio further activated the downstream caspases cascade. ROT promoted the LC3BII/I ratio and p62 levels; however, different ROA doses resulted in different effects on autophagy while inducing PD-like impairments in SH-SY5Y cells.

Carbon Nanotube-Mediated Delivery of PTEN Variants: In Vitro Antitumor Activity in Breast Cancer Cells

Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) is a crucial tumor suppressor protein with frequent mutations and alterations. Although protein therapeutics are already integral to numerous medical fields, their potential remains nascent. This study aimed to investigate the impact of stable, unphosphorylated recombinant human full-length PTEN and its truncated variants, regarding their tumor suppression activity with multiwalled-carbon nanotubes (MW-CNTs) as vehicles for their delivery in breast cancer cells (T-47D, ZR-75-1, and MCF-7). The cloning, overexpression, and purification of PTEN variants were achieved from E. coli, followed by successful binding to CNTs. Cell incubation with protein-functionalized CNTs revealed that the full-length PTEN-CNTs significantly inhibited cancer cell growth and stimulated apoptosis in ZR-75-1 and MCF-7 cells, while truncated PTEN fragments on CNTs had a lesser effect. The N-terminal fragment, despite possessing the active site, did not have the same effect as the full length PTEN, emphasizing the necessity of interaction with the C2 domain in the C-terminal tail. Our findings highlight the efficacy of full-length PTEN in inhibiting cancer growth and inducing apoptosis through the alteration of the expression levels of key apoptotic markers. In addition, the utilization of carbon nanotubes as a potent PTEN protein delivery system provides valuable insights for future applications in in vivo models and clinical studies.

BLM and BRCA1-BARD1 coordinate complementary mechanisms of joint DNA molecule resolution

The Bloom syndrome helicase BLM interacts with topoisomerase IIIα (TOP3A), RMI1, and RMI2 to form the BTR complex, which dissolves double Holliday junctions and DNA replication intermediates to promote sister chromatid disjunction before cell division. In its absence, structure-specific nucleases like the SMX complex (comprising SLX1-SLX4, MUS81-EME1, and XPF-ERCC1) can cleave joint DNA molecules instead, but cells deficient in both BTR and SMX are not viable. Here, we identify a negative genetic interaction between BLM loss and deficiency in the BRCA1-BARD1 tumor suppressor complex. We show that this is due to a previously overlooked role for BARD1 in recruiting SLX4 to resolve DNA intermediates left unprocessed by BLM in the preceding interphase. Consequently, cells with defective BLM and BRCA1-BARD1 accumulate catastrophic levels of chromosome breakage and micronucleation, leading to cell death. Thus, we reveal mechanistic insights into SLX4 recruitment to DNA lesions, with potential clinical implications for treating BRCA1-deficient tumors.

Catalytic activity and autoprocessing of murine caspase-11 mediate noncanonical inflammasome assembly in response to cytosolic LPS

Inflammatory caspases are cysteine protease zymogens whose activation following infection or cellular damage occurs within supramolecular organizing centers (SMOCs) known as inflammasomes. Inflammasomes recruit caspases to undergo proximity-induced autoprocessing into an enzymatically active form that cleaves downstream targets. Binding of bacterial LPS to its cytosolic sensor, caspase-11 (Casp11), promotes Casp11 aggregation within a high-molecular-weight complex known as the noncanonical inflammasome, where it is activated to cleave gasdermin D and induce pyroptosis. However, the cellular correlates of Casp11 oligomerization and whether Casp11 forms an LPS-induced SMOC within cells remain unknown. Expression of fluorescently labeled Casp11 in macrophages revealed that cytosolic LPS induced Casp11 speck formation. Unexpectedly, catalytic activity and autoprocessing were required for Casp11 to form LPS-induced specks in macrophages. Furthermore, both catalytic activity and autoprocessing were required for Casp11 speck formation in an ectopic expression system, and processing of Casp11 via ectopically expressed TEV protease was sufficient to induce Casp11 speck formation. These data reveal a previously undescribed role for Casp11 catalytic activity and autoprocessing in noncanonical inflammasome assembly, and shed new light on the molecular requirements for noncanonical inflammasome assembly in response to cytosolic LPS.

Tetraacetyl riboflavin derivative mediates caspase 3/7 activation via MAPK in A431 cells upon blue light influence

An acetylated riboflavin derivative, 3-methyl-tetraacetyl riboflavin (3MeTARF), is a compound with high photostability and photophysical properties similar to riboflavin, including the ability to photogenerate singlet oxygen. In the present study, we compared the effects of irradiation on A431 cancer cells with blue LED light (438 nm) in the presence of 3MeTARF and riboflavin on MAPK phosphorylation, apoptosis, caspase 3/7 activation and PARP cleavage. We observed that photogenerated oxidative stress in this reaction activates MAPK by increasing phosphorylation of p38 and JNK proteins. Preincubation of cells with inhibitors specific for phosphorylation of p38 and JNK proteins (SB203580, SP600125), respectively, results in decreased caspase 3/7 activation and PARP cleavage. We showed that the tetraacetyl derivative more effectively activates MAPK and skin cancer cell death compared to riboflavin. These data, together with results of our previous study, support the hypothesis that 3MeTARF, of riboflavin, might be more useful and desirable as a compound for use in photodynamic oxidation processes, including its therapeutic potential.

Optogenetic induction of caspase-8 mediated apoptosis by employing Arabidopsis cryptochrome 2

Apoptosis, a programmed cell death mechanism, is a regulatory process controlling cell proliferation as cells undergo demise. Caspase-8 serves as a pivotal apoptosis-inducing factor that initiates the death receptor-mediated apoptosis pathway. In this investigation, we have devised an optogenetic method to swiftly modulate caspase-8 activation in response to blue light. The cornerstone of our optogenetic tool relies on the PHR domain of Arabidopsis thaliana cryptochrome 2, which self-oligomerizes upon exposure to blue light. In this study, we have developed two optogenetic approaches for rapidly controlling caspase-8 activation in response to blue light in cellular systems. The first strategy, denoted as Opto-Casp8-V1, entails the fusion expression of the Arabidopsis blue light receptor CRY2 N-terminal PHR domain with caspase-8. The second strategy, referred to as Opto-Casp8-V2, involves the independent fusion expression of caspase-8 with the PHR domain and the CRY2 blue light-interacting protein CIB1 N-terminal CIB1N. Upon induction with blue light, PHR undergoes aggregation, leading to caspase-8 aggregation. Additionally, the blue light-dependent interaction between PHR and CIB1N also results in caspase-8 aggregation. We have validated these strategies in both HEK293T and HeLa cells. The findings reveal that both strategies are capable of inducing apoptosis, with Opto-Casp8-V2 demonstrating significantly superior efficiency compared to Opto-Casp8-V1.

Nitric oxide and thioredoxin modulate the activity of caspase 9 in HepG2 cells

The interdependent and finely tuned balance between the well-established redox-based modification, S-nitrosylation, and its counteractive mechanism of S-nitrosothiol degradation, i.e., S-denitrosylation of biological protein or non-protein thiols defines the cellular fate in the context of redox homeostasis. S-nitrosylation of cysteine residues by S-nitrosoglutathione, S-nitroso-L-cysteine-like physiological and S-nitroso-L-cysteine ethyl ester-like synthetic NO donors inactivate Caspase-3, 8, and 9, thereby hindering their apoptotic activity. However, spontaneous restoration of their activity upon S-denitrosylation of S-nitrosocaspases into their reduced, free thiol active states, aided by the members of the ubiquitous cellular redoxin (thioredoxin/ thioredoxin reductase/ NADPH) and low molecular weight dithiol (lipoic acid/ lipoamide dehydrogenase/ dihydrolipoic acid/ NADPH) systems imply a direct relevance to their proteolytic activities and further downstream signaling cascades. Additionally, our previous and current findings offer crucial insight into the concept of redundancy between thioredoxin and lipoic acid systems, and the redox-modulated control of the apoptotic and proteolytic activity of caspases, triggering their cyto- and neurotoxic effects in response to nitro-oxidative stress. Thus, this might lay the foundation for the exogenous introduction of precise and efficient NO or related donor drug delivery systems that can directly participate in catering to the S-(de)-nitrosylation-mediated functional outcomes of the cysteinyl proteases in pathophysiological settings.

A Cryptosporidium parvum vaccine candidate effect on immunohistochemical profiling of CD4+, CD8+, Caspase-3 and NF-κB in mice

BACKGROUND

Cryptosporidium parvum is a protozoan parasite of medical and veterinary importance that causes neonatal diarrhea in many vertebrate hosts. In this study, we evaluated the efficacy of an affinity-purified antigen as a C. parvum vaccine candidate using ileal and liver tissues of experimentally infected neonatal mice by immunohistochemical profiling and immune scoring of CD4+, CD8+, Caspase-3, and nuclear factor kappa B (NF-κB). This vaccine was prepared from the C. parvum oocysts antigen using immune affinity chromatography with cyanogen bromide-activated Sepharose-4B beads.

METHODS

Thirty neonatal mice were divided into three groups (10 mice/group): (1) non-immunized non-infected, (2) non-immunized infected (using gastric tubes with a single dose of 1 × 105 of C. parvum oocysts in 250 µl PBS solution 1 h before a meal) and (3) immunized (twice with 40 µg/kg of purified C. parvum antigen at 2-week intervals and then infected with 1 × 105 C. parvum oocysts simultaneously with the second group). After euthanizing the animals on the 10th day, post-infection, their ileal and liver tissues were collected and prepared for immunohistochemistry (IHC) staining to detect CD4+, CD8+, Caspase-3, and NF-κB levels, which are indicators for T helper cells, cytotoxic T cells, apoptosis, and inflammation, respectively.

RESULTS

The IHC results showed that CD4+, CD8+, Caspase-3, and NF-κB expression varied significantly (P < 0.001) in both organs in all the groups. We also recorded high CD4+ levels and low CD8+ expression in the non-immunized non-infected mice tissues, while the opposite was observed in the non-immunized infected mice tissues. In the immunized infected mice, the CD4+ level was higher than CD8 + in both organs. While the Caspase-3 levels were higher in the ileal tissue of non-immunized infected than immunized infected mice ileal tissues, the reverse was seen in the liver tissues of both groups. Furthermore, NF-κB expression was higher in the liver tissues of non-immunized infected mice than in immunized infected mice tissues. Therefore, the IHC results and immune-scoring program revealed a significant difference (P < 0.001) in the CD4+, CD8+, Caspase-3, and NF-κB expression levels in both ileal and liver tissues of all mice groups, which might be necessary for immunomodulation in these tissues.

CONCLUSIONS

The improvement observed in the immunized infected mice suggests that this vaccine candidate might protect against cryptosporidiosis.

What are NLRP3-ASC specks? an experimental progress of 22 years of inflammasome research

Speck assembly is the hallmark of NLRP3 inflammasome activation. The 1µm structure comprising of NLRP3 and ASC is the first observable phenotype of NLRP3 activation. While the common consensus is that the specks are the site of inflammasome activity, no direct experimental evidence exists to support this notion. In these 22 years, since the inflammasome discovery, several research studies have been published which directly or indirectly support or refute the idea of speck being the inflammasome. This review compiles the data from two decades of research to answer a long-standing question: "What are NLRP3-ASC specks?"

BMP-induced non-canonical signaling is upregulated during autophagy-mediated regeneration in inflamed mesothelial cells

Previously, we showed that after Freund's adjuvant-induced peritonitis, rat mesothelial cells regain their epithelial phenotype through mesenchymal-epithelial transition (MET) accompanied by autophagy. Since bone morphogenetic proteins (BMPs) are well-known MET-inducers, we were interested in the potential expression of BMPs and BMP-induced pathways. Although mesothelial cells expressed lower amounts of BMP7, its level in the peritoneal cavity and mesothelial synthesis of BMP4 were significantly increased during inflammation. BMPR1A and BMPR2 were also significantly expressed. Expression of transforming growth factor beta-activated kinase (TAK1) and c-Jun NH2-terminal kinases (JNK1-JNK2) were more intense than that of phosphorylated Mothers Against Decapentaplegic homolog 1/5 (p-SMAD1/5), confirming that the non-canonical pathway of BMPs prevailed in our model. JNK signaling through B-cell lymphoma-2 (Bcl-2) can contribute to Beclin-1 activation. We demonstrated that TAK1-JNK-Bcl-2 signaling was upregulated simultaneously with the autophagy-mediated regeneration. A further goal of our study was to prove the regenerative role of autophagy after inflammation. We used a specific inhibitor, bafilomycin A1 (BafA1), and found that BafA1 treatment decreased the expression of microtubule-associated protein 1A/1B-light chain 3 (LC3B) and resulted in morphological signs of cell death in inflamed mesothelial cells indicating that if autophagy is arrested, regeneration turns into cell death and consequently, mesothelial cells die.

Mating modifies the expression of crucial oxidative-reductive transcripts in the pig oviductal sperm reservoir: is the female ensuring sperm survival?

Background

Mating induces large changes in the female genital tract, warranting female homeostasis and immune preparation for pregnancy, including the preservation of crucial oxidative status among its pathways. Being highly susceptible to oxidative stress, sperm survival and preserved function depend on the seminal plasma, a protection that is removed during sperm handling but also after mating when spermatozoa enter the oviduct. Therefore, it is pertinent to consider that the female sperm reservoir takes up this protection, providing a suitable environment for sperm viability. These aspects have not been explored despite the increasing strategies in modulating the female status through diet control and nutritional supplementation.

Aims

To test the hypothesis that mating modifies the expression of crucial oxidative-reductive transcripts across the entire pig female genital tract (cervix to infundibulum) and, particularly in the sperm reservoir at the utero-tubal junction, before ovulation, a period dominated by estrogen stimulation of ovarian as well as of seminal origin.

Methods

The differential expression of estrogen (ER) and progesterone (PR) receptors and of 59 oxidative-reductive transcripts were studied using a species-specific microarray platform, in specific segments of the peri-ovulatory sow reproductive tract in response to mating.

Results

Mating induced changes along the entire tract, with a conspicuous downregulation of both ER and PR and an upregulation of superoxide dismutase 1 (SOD1), glutaredoxin (GLRX3), and peroxiredoxin 1 and 3 (PRDX1, PRDX3), among other NADH Dehydrogenase Ubiquinone Flavoproteins, in the distal uterus segment. These changes perhaps helped prevent oxidative stress in the area adjacent to the sperm reservoir at the utero-tubal junction. Concomitantly, there were a downregulation of catalase (CAT) and NADH dehydrogenase (ubiquinone) oxidoreductases 1 beta subcomplex, subunit 1 (NDUFB1) in the utero-tubal junction alongside an overall downregulation of CAT, SOD1, and PRDX3 in the ampullar and infundibulum segments.

Conclusions

Natural mating is an inducer of changes in the expression of female genes commanding antioxidant enzymes relevant for sperm survival during sperm transport, under predominant estrogen influence through the bloodstream and semen. The findings could contribute to the design of new therapeutics for the female to improve oxidative-reductive balance.

Oligomeric states of ASC specks regulate inflammatory responses by inflammasome in the extracellular space

Inflammasomes are multi-protein complexes and play a crucial role in host defense against pathogens. Downstream inflammatory responses through inflammasomes are known to be related to the oligomerization degree of ASC specks, but the detailed mechanism still remains unexplored. Here, we demonstrate that oligomerization degrees of ASC specks regulate the caspase-1 activation in the extracellular space. A protein binder specific for a pyrin domain (PYD) of ASC (ASCPYD) was developed, and structural analysis revealed that the protein binder effectively inhibits the interaction between PYDs, disassembling ASC specks into low oligomeric states. ASC specks with a low oligomerization degree were shown to enhance the activation of caspase-1 by recruiting and processing more premature caspase-1 through interactions between CARD of caspase-1 (caspase-1CARD) and CARD of ASC (ASCCARD). These findings can provide insight into controlling the inflammasome-mediated inflammatory process as well as the development of inflammasome-targeting drugs.

CARD-only proteins regulate in vivo inflammasome responses and ameliorate gout

Inflammatory responses are crucial for controlling infections and initiating tissue repair. However, excessive and uncontrolled inflammation causes inflammatory disease. Processing and release of the pro-inflammatory cytokines interleukin-1β (IL-1β) and IL-18 depend on caspase-1 activation within inflammasomes. Assembly of inflammasomes is initiated upon activation of cytosolic pattern recognition receptors (PRRs), followed by sequential polymerization of pyrin domain (PYD)-containing and caspase recruitment domain (CARD)-containing proteins mediated by homotypic PYD and CARD interactions. Small PYD- or CARD-only proteins (POPs and COPs, respectively) evolved in higher primates to target these crucial interactions to limit inflammation. Here, we show the ability of COPs to regulate inflammasome activation by modulating homotypic CARD-CARD interactions in vitro and in vivo. CARD16, CARD17, and CARD18 displace crucial CARD interactions between caspase-1 proteins through competitive binding and ameliorate uric acid crystal-mediated NLRP3 inflammasome activation and inflammatory disease. COPs therefore represent an important family of inflammasome regulators and ameliorate inflammatory disease.

Uncoupled pyroptosis and IL-1β secretion downstream of inflammasome signaling

Inflammasomes are supramolecular platforms that organize in response to various damage-associated molecular patterns and pathogen-associated molecular patterns. Upon activation, inflammasome sensors (with or without the help of ASC) activate caspase-1 and other inflammatory caspases that cleave gasdermin D and pro-IL-1β/pro-IL-18, leading to pyroptosis and mature cytokine secretion. Pyroptosis enables intracellular pathogen niche disruption and intracellular content release at the cost of cell death, inducing pro-inflammatory responses in the neighboring cells. IL-1β is a potent pro-inflammatory regulator for neutrophil recruitment, macrophage activation, and T-cell expansion. Thus, pyroptosis and cytokine secretion are the two main mechanisms that occur downstream of inflammasome signaling; they maintain homeostasis, drive the innate immune response, and shape adaptive immunity. This review aims to discuss the possible mechanisms, timing, consequences, and significance of the two uncoupling preferences downstream of inflammasome signaling. While pyroptosis and cytokine secretion may be usually coupled, pyroptosis-predominant and cytokine-predominant uncoupling are also observed in a stimulus-, cell type-, or context-dependent manner, contributing to the pathogenesis and development of numerous pathological conditions such as cryopyrin-associated periodic syndromes, LPS-induced sepsis, and Salmonella enterica serovar Typhimurium infection. Hyperactive cells consistently release IL-1β without LDH leakage and pyroptotic death, thereby leading to prolonged inflammation, expanding the lifespans of pyroptosis-resistant neutrophils, and hyperactivating stimuli-challenged macrophages, dendritic cells, monocytes, and specific nonimmune cells. Death inflammasome activation also induces GSDMD-mediated pyroptosis with no IL-1β secretion, which may increase lethality in vivo. The sublytic GSDMD pore formation associated with lower expressions of pyroptotic components, GSDMD-mediated extracellular vesicles, or other GSDMD-independent pathways that involve unconventional secretion could contribute to the cytokine-predominant uncoupling; the regulation of caspase-1 dynamics, which may generate various active species with different activities in terms of GSDMD or pro-IL-1β, could lead to pyroptosis-predominant uncoupling. These uncoupling preferences enable precise reactions to different stimuli of different intensities under specific conditions at the single-cell level, promoting cooperative cell and host fate decisions and participating in the pathogen "game". Appropriate decisions in terms of coupling and uncoupling are required to heal tissues and eliminate threats, and further studies exploring the inflammasome tilt toward pyroptosis or cytokine secretion may be helpful.

Mitigating Apoptotic and Inflammatory Signaling via Global Caspase Inhibition in Hibernating Ground Squirrels, Spermophilus lateralis

AbstractIn most systems, the caspase cascade is activated during cellular stress and results in inflammation and apoptosis. Hibernators experience stressors such as extremely low body temperatures, bradycardia, possible ischemia and reperfusion, and acidosis. However, widespread inflammation and apoptosis would represent an energetic expense that is incompatible with hibernation. To better understand global caspase regulation during hibernation, we employed a systems-level approach and analyzed 11 caspases in ground squirrel liver that are involved in inflammatory (caspases 1, 4, 5, 11, and 12) and apoptotic (caspases 2, 6, 7, 8, 9, and 10) pathways. Western blots revealed liberation of active forms for two inflammatory (caspases 11 and 12) and two apoptotic (caspases 6 and 9) caspases during hibernation (e.g., p15, the most active fragment of caspase 6, increased 8.26±0.70-fold in interbout-aroused animals). We used specific peptide substrates to interrogate the four seemingly activated caspases and demonstrated no expected increases in proteolytic activity. Specific targets of these four caspases were similarly not cleaved, demonstrating that initiation of caspase activation may occur without concomitant downstream effects. Similarly, we found no evidence for upstream activation for caspase 9 signaling based on permeabilization of the outer mitochondrial membrane. We contend that these caspases are suppressed after seeming activation during hibernation. Incomplete caspase signaling is effectively mitigating the induction of widespread inflammation and apoptosis during hibernation.

Molecular Characteristics of Cell Pyroptosis and Its Inhibitors: A Review of Activation, Regulation, and Inhibitors

Pyroptosis is an active and ordered form of programmed cell death. The signaling pathways of pyroptosis are mainly divided into canonical pathways mediated by caspase-1 and noncanonical pathways mediated by caspase-11. Cell pyroptosis is characterized by the activation of inflammatory caspases (mainly caspase-1, 4, 5, 11) and cleavage of various members of the Gasdermin family to form membrane perforation components, leading to cell membrane rupture, inflammatory mediators release, and cell death. Moderate pyroptosis is an innate immune response that fights against infection and plays an important role in the occurrence and development of the normal function of the immune system. However, excessive pyroptosis occurs and leads to immune disorders in many pathological conditions. Based on canonical pathways, research on pyroptosis regulation has demonstrated several pyroptotic inhibitors, including small-molecule drugs, natural products, and formulations of traditional Chinese medicines. In this paper, we review the characteristics and molecular mechanisms of pyroptosis, summarize inhibitors of pyroptosis, and propound that herbal medicines should be a focus on the research and development for pyroptosis blockers.

Live imaging of apoptotic signaling flow using tunable combinatorial FRET-based bioprobes for cell population analysis of caspase cascades

Understanding cellular signaling flow is required to comprehend living organisms. Various live cell imaging tools have been developed but challenges remain due to complex cross-talk between pathways and response heterogeneities among cells. We have focused on multiplex live cell imaging for statistical analysis to address the difficulties and developed simple multiple fluorescence imaging system to quantify cell signaling at single-cell resolution using Förster Resonance Energy Transfer (FRET)-based chimeric molecular sensors comprised of fluorescent proteins and dyes. The dye-fluorescent protein conjugate is robust for a wide selection of combinations, facilitating rearrangement for coordinating emission profile of molecular sensors to adjust for visualization conditions, target phenomena, and simultaneous use. As the molecular sensor could exhibit highly sensitive in detection for protease activity, we customized molecular sensor of caspase-9 and combine the established sensor for caspase-3 to validate the system by observation of caspase-9 and -3 dynamics simultaneously, key signaling flow of apoptosis. We found cumulative caspase-9 activity rather than reaction rate inversely regulated caspase-3 execution times for apoptotic cell death. Imaging-derived statistics were thus applied to discern the dominating aspects of apoptotic signaling unavailable by common live cell imaging and proteomics protein analysis. Adopted to various visualization targets, the technique can discriminate between rivalling explanations and should help unravel other protease involved signaling pathways.

The impact of dolutegravir-based combination antiretroviral therapy on the spermatozoa and fertility parameters of men living with human immunodeficiency virus

The factors responsible for this reported fertility decline among human immunodeficiency virus (HIV) positive men is yet to be determined. This study is aimed at investigating the impact of HIV or combination antiretroviral therapy (cART) on sperm cells, reproductive hormones, oxidative stress markers, apoptosis, and sperm DNA fragmentation of men living with HIV. Twenty-one men living with HIV gave their written informed consent to participate in this study. Only 11 of the participants successfully donated blood and semen before and after 3 months of their treatment with cART. Semen, reproductive hormones, oxidative stress biomarkers, and DNA fragmentation were analysed. Data were subjected to Wilcoxon matched pairs signed rank test (ethical approval: CMUL/HREC/09/19/614). There was a significant decrease in viral load of HIV (p < 0.01), and a marked increase in progressive and total sperm motility. Total sperm count, morphology, and vitality had no significant change after 3 months of treatment with cART however, there was a significant increase (p < 0.05) in testosterone from 2.48 to 3.68 ng/ml, but luteinizing hormone decreased significantly (p < 0.05) from 9.6 to 6.5 mIU/ml. In addition, sperm DNA fragmentation increased significantly (p < 0.01). Conversely, viral load, and catalase decreased significantly, but no significant difference in malondialdehyde. This study showed that HIV depleted testosterone and impaired sperm motility which may negatively affect the fertility potential of men living with HIV. It also showed that adherence to cART (a combination of tenofovir, lamivudine, and dolutegravir) reduces the viral load and reverses the deleterious effects of cART albeit, cART appears to be toxic at subcellular spermatogenic levels.

The strategies of NLRP3 inflammasome to combat Toxoplasma gondii

Infection with the protozoan parasite Toxoplasma gondii (T. gondii) results in the activation of nucleotide-binding domain leucine-rich repeat containing receptors (NLRs), which in turn leads to inflammasome assembly and the subsequent activation of caspase-1, secretion of proinflammatory cytokines, and pyroptotic cell death. Several recent studies have addressed the role of the NLRP3 inflammasome in T. gondii infection without reaching a consensus on its roles. Moreover, the mechanisms of NLRP3 inflammasome activation in different cell types remain unknown. Here we review current research on the activation and specific role of the NLRP3 inflammasome in T. gondii infection.

Craspase is a CRISPR RNA-guided, RNA-activated protease

The CRISPR-Cas type III-E RNA-targeting effector complex gRAMP/Cas7-11 is associated with a caspase-like protein (TPR-CHAT/Csx29) to form Craspase (CRISPR-guided caspase). Here, we use cryo-electron microscopy snapshots of Craspase to explain its target RNA cleavage and protease activation mechanisms. Target-guide pairing extending into the 5' region of the guide RNA displaces a gating loop in gRAMP, which triggers an extensive conformational relay that allosterically aligns the protease catalytic dyad and opens an amino acid side-chain-binding pocket. We further define Csx30 as the endogenous protein substrate that is site-specifically proteolyzed by RNA-activated Craspase. This protease activity is switched off by target RNA cleavage by gRAMP and is not activated by RNA targets containing a matching protospacer flanking sequence. We thus conclude that Craspase is a target RNA-activated protease with self-regulatory capacity.

Curcuma aeruginosa Roxb. exhibits cytotoxicity in A-549 and HeLa cells by inducing apoptosis through caspase-dependent pathways

The aim of the current study was to examine the efficacy of the leaf, stem and rhizome of Curcuma aeruginosa Roxb. for their phytochemical content, antioxidant and anti-cancer activities. The different parts of C. aeruginosa were subjected to sequential extraction to give three fractions viz., hexane, ethyl acetate and methanol extract. The cytotoxic effect and the mode of action against A-549 human lung adenocarcinoma and HeLa cell lines were examined. C. aeruginosa presented no significant toxic effect in normal human lung cells (L-132). The methanol extracts were found to be the most cytotoxic and further investigation was carried out to understand the effects. The methanol extracts induced DNA damage after 24 h with significant increase in tail DNA and tail moment when compared to untreated control. Up-regulation in the expression of the caspase - 8 and - 3 activity was observed after 48 h of treatment. The mechanism of cell death and apoptosis induced by the methanol extracts on A549 and HeLa cells were studied using fluorescent staining. Bioactive compounds detected from the HPLC revealed phenol and flavonoid compounds: Gallic acid, quercetin, caffeic acid, kaempferol, rutin, coumaric acid and naringenin. GC-MS results identified the presence of sesquiterpenoids: α-curcumene, curzerene curcumenol, curzerenone epicurzerenone, caryophyllene oxide and diterpenoid, andrographolide. These compounds are known for inducing apoptosis in human cancer cells through caspase - dependent pathways. Therefore, C. aeruginosa and its potential to induce apoptosis in cancer cells suggest that they have potential in medical applications.

GSDMD-miR-223-NLRP3 axis involved in B(a)P-induced inflammatory injury of alveolar epithelial cells

Benzo(a)pyrene [B(a)P], a ubiquitous environmental pollutant, causes lung inflammatory damage. Pyroptosis，a new inflammation-dependent programmed cell death, happened when pyroptosis-related GSDMD is activated mediated by NLRP3 inflammasome. microRNA-223 (miRNA-223) is involved in inflammatory diseases by regulating NLRP3. However, whether GSDMD regulate NLRP3 inflammasome through miR-223 in B(a)P induced lung inflammatory injury remain unknown. In this study, alveolar epithelial cells (A549) were stimulated with 0, 2, 4, 8 μM B(a)P for 12 h or 24 h. The inflammatory injury and pyroptosis were determined. And the activation of NLRP3 inflammasomes and the level of miRNA-223 were detected. Then, the change of inflammatory injury and activation of NLRP3 inflammasomes in B(a)P-induced A549 cells were detected after inhibiting of GSDMD or miR-223 using siRNA-GSDMD (siGSDMD) or miR-223 inhibitor, respectively. Our results indicated that after B(a)P exposure, TNF-α and IL-6 in the supernatant were increased. Transmission electron microscope (TEM) results showed that A549 cells were obviously swollen and the cell membrane ruptured. Hoechest33342/PI staining showed that pyroptosis occurred. NLRP3, IL-1β, IL-18, GSDMD, GSDMD-N, pro caspase-1 and cleaved caspase-1 were significantly increased. Additionally, after transfecting with siGSDMD in B(a)P-induced A549 cells, the expression level of miR-223 was significantly increased. But IL-6 and TNF-α in the supernatant, the expression of NLRP3, IL-1β, IL-18 and cleaved caspase-1 protein were also decreased. And after inhibiting miR-223 in B(a)P-induced A549 cells, the expression of TNF-α and IL-6 in the supernatant, the protein expression of NLRP3, IL-1β, IL-18 and cleaved caspase-1 were increased. In conclusion, GSDMD may regulate NLRP3 inflammasome through miR-223, which is involved in B(a)P induced inflammatory damage in A549 cells.

Non-Canonical Roles of Apoptotic Caspases in the Nervous System

Caspases are a family of cysteine proteases that predominantly cleave their substrates after aspartic acid residues. Much of what we know of caspases emerged from investigation a highly conserved form of programmed cell death called apoptosis. This form of cell death is regulated by several caspases, including caspase-2, caspase-3, caspase-7, caspase-8 and caspase-9. However, these “killer” apoptotic caspases have emerged as versatile enzymes that play key roles in a wide range of non-apoptotic processes. Much of what we understand about these non-apoptotic roles is built on work investigating how “killer” caspases control a range of neuronal cell behaviors. This review will attempt to provide an up to date synopsis of these roles.

Over Fifty Years of Life, Death, and Cannibalism: A Historical Recollection of Apoptosis and Autophagy

Research in biomedical sciences has changed dramatically over the past fifty years. There is no doubt that the discovery of apoptosis and autophagy as two highly synchronized and regulated mechanisms in cellular homeostasis are among the most important discoveries in these decades. Along with the advancement in molecular biology, identifying the genetic players in apoptosis and autophagy has shed light on our understanding of their function in physiological and pathological conditions. In this review, we first describe the history of key discoveries in apoptosis with a molecular insight and continue with apoptosis pathways and their regulation. We touch upon the role of apoptosis in human health and its malfunction in several diseases. We discuss the path to the morphological and molecular discovery of autophagy. Moreover, we dive deep into the precise regulation of autophagy and recent findings from basic research to clinical applications of autophagy modulation in human health and illnesses and the available therapies for many diseases caused by impaired autophagy. We conclude with the exciting crosstalk between apoptosis and autophagy, from the early discoveries to recent findings.

Up-regulation of apoptotic- and cell survival-related gene pathways following exposures of western corn rootworm to B. thuringiensis crystalline pesticidal proteins in transgenic maize roots

BACKGROUND

Resistance of pest insect species to insecticides, including B. thuringiensis (Bt) pesticidal proteins expressed by transgenic plants, is a threat to global food security. Despite the western corn rootworm, Diabrotica virgifera virgifera, being a major pest of maize and having populations showing increasing levels of resistance to hybrids expressing Bt pesticidal proteins, the cell mechanisms leading to mortality are not fully understood.

RESULTS

Twenty unique RNA-seq libraries from the Bt susceptible D. v. virgifera inbred line Ped12, representing all growth stages and a range of different adult and larval exposures, were assembled into a reference transcriptome. Ten-day exposures of Ped12 larvae to transgenic Bt Cry3Bb1 and Gpp34/Tpp35Ab1 maize roots showed significant differential expression of 1055 and 1374 transcripts, respectively, compared to cohorts on non-Bt maize. Among these, 696 were differentially expressed in both Cry3Bb1 and Gpp34/Tpp35Ab1 maize exposures. Differentially-expressed transcripts encoded protein domains putatively involved in detoxification, metabolism, binding, and transport, were, in part, shared among transcripts that changed significantly following exposures to the entomopathogens Heterorhabditis bacteriophora and Metarhizium anisopliae. Differentially expressed transcripts in common between Bt and entomopathogen treatments encode proteins in general stress response pathways, including putative Bt binding receptors from the ATP binding cassette transporter superfamily. Putative caspases, pro- and anti-apoptotic factors, as well as endoplasmic reticulum (ER) stress-response factors were identified among transcripts uniquely up-regulated following exposure to either Bt protein.

CONCLUSIONS

Our study suggests that the up-regulation of genes involved in ER stress management and apoptotic progression may be important in determining cell fate following exposure of susceptible D. v. virgifera larvae to Bt maize roots. This study provides novel insights into insect response to Bt intoxication, and a possible framework for future investigations of resistance mechanisms.

Exogenous Introduction of Initiator and Executioner Caspases Results in Different Apoptotic Outcomes

The balance of pro-apoptotic and pro-survival proteins defines a cell's fate. These processes are controlled through an interdependent and finely tuned protein network that enables survival or leads to apoptotic cell death. The caspase family of proteases is central to this apoptotic network, with initiator and executioner caspases, and their interaction partners, regulating and executing apoptosis. In this work, we interrogate and modulate this network by exogenously introducing specific initiator or executioner caspase proteins. Each caspase is exogenously introduced using redox-responsive polymeric nanogels. Although caspase-3 might be expected to be the most effective due to the centrality of its role in apoptosis and its heightened catalytic efficiency relative to other family members, we observed that caspase-7 and caspase-9 are the most effective at inducing apoptotic cell death. By critically analyzing the introduced activity of the delivered caspase, the pattern of substrate cleavage, as well as the ability to activate endogenous caspases, we conclude that the efficacy of each caspase correlated with the levels of pro-survival factors that both directly and indirectly impact the introduced caspase. These findings lay the groundwork for developing methods for exogenous introduction of caspases as a therapeutic option that can be tuned to the apoptotic balance in a proliferating cell.

Galectin-3 promotes noncanonical inflammasome activation through intracellular binding to lipopolysaccharide glycans

Cytosolic lipopolysaccharides (LPSs) bind directly to caspase-4/5/11 through their lipid A moiety, inducing inflammatory caspase oligomerization and activation, which is identified as the noncanonical inflammasome pathway. Galectins, β-galactoside-binding proteins, bind to various gram-negative bacterial LPS, which display β-galactoside-containing polysaccharide chains. Galectins are mainly present intracellularly, but their interactions with cytosolic microbial glycans have not been investigated. We report that in cell-free systems, galectin-3 augments the LPS-induced assembly of caspase-4/11 oligomers, leading to increased caspase-4/11 activation. Its carboxyl-terminal carbohydrate-recognition domain is essential for this effect, and its N-terminal domain, which contributes to the self-association property of the protein, is also critical, suggesting that this promoting effect is dependent on the functional multivalency of galectin-3. Moreover, galectin-3 enhances intracellular LPS-induced caspase-4/11 oligomerization and activation, as well as gasdermin D cleavage in human embryonic kidney (HEK) 293T cells, and it additionally promotes interleukin-1β production and pyroptotic death in macrophages. Galectin-3 also promotes caspase-11 activation and gasdermin D cleavage in macrophages treated with outer membrane vesicles, which are known to be taken up by cells and release LPSs into the cytosol. Coimmunoprecipitation confirmed that galectin-3 associates with caspase-11 after intracellular delivery of LPSs. Immunofluorescence staining revealed colocalization of LPSs, galectin-3, and caspase-11 independent of host N-glycans. Thus, we conclude that galectin-3 amplifies caspase-4/11 oligomerization and activation through LPS glycan binding, resulting in more intense pyroptosis-a critical mechanism of host resistance against bacterial infection that may provide opportunities for new therapeutic interventions.

Mutagenic Consequences of Sublethal Cell Death Signaling

Many human cancers exhibit defects in key DNA damage response elements that can render tumors insensitive to the cell death-promoting properties of DNA-damaging therapies. Using agents that directly induce apoptosis by targeting apoptotic components, rather than relying on DNA damage to indirectly stimulate apoptosis of cancer cells, may overcome classical blocks exploited by cancer cells to evade apoptotic cell death. However, there is increasing evidence that cells surviving sublethal exposure to classical apoptotic signaling may recover with newly acquired genomic changes which may have oncogenic potential, and so could theoretically spur the development of subsequent cancers in cured patients. Encouragingly, cells surviving sublethal necroptotic signaling did not acquire mutations, suggesting that necroptosis-inducing anti-cancer drugs may be less likely to trigger therapy-related cancers. We are yet to develop effective direct inducers of other cell death pathways, and as such, data regarding the consequences of cells surviving sublethal stimulation of those pathways are still emerging. This review details the currently known mutagenic consequences of cells surviving different cell death signaling pathways, with implications for potential oncogenic transformation. Understanding the mechanisms of mutagenesis associated (or not) with various cell death pathways will guide us in the development of future therapeutics to minimize therapy-related side effects associated with DNA damage.

A unique understanding of traditional medicine of pomegranate, Punica granatum L. and its current research status

ETHNOPHARMACOLOGICAL RELEVANCE

Pomegranate, Punica granatum L., has been used in traditional medicine in China and several regions of the world including Ayurveda, Islamic, and Persian for the treatment of atherosclerosis, diabetes, hypertension, hyperlipidemia, and several types of cancer, as well as for peptic ulcer and oral diseases for hundreds of years. Presently, pomegranate is treated as both a "medicine food homology" herbal medicine and a healthy food supplemental product.

AIM OF THE STUDY

The aim of this work is to develop an overview of pomegranate in the context of the status of its traditional medicine theories, the spread along the Silk Road, ethnopharmacological uses, chemical compositions, pharmacological activities, toxicology, and the involved pathways.

MATERIALS AND METHODS

Information on P. granatum L. was acquired from published materials, including monographs on medicinal plants, ancient and modern recorded classical texts; and pharmacopoeias and electronic databases (PubMed, Science Direct, Web of Science, Google Scholar, CNKI, and Wanfang Data).

RESULTS

Pomegranate has been used in many traditional medical systems throughout history. It is widely cultivated in Central Asia and spread throughout China along the Silk Road. Many phytochemicals, such as tannins, organic acids, flavonoids, alkaloids, and volatile oils have been identified from different parts of pomegranate, these compounds have a wide range of activities, including antioxidant, antimicrobial, and anti-oncogenic properties, as well as conferring resistance to cerebrovascular disease. Furthermore, A summary of the four promising pharmacological pathways is provided.

CONCLUSIONS

The traditional uses, chemical compositions, pharmacological activities, and signaling pathways of pomegranate are summarized comprehensively in the review. It can be treated as a guidance for the future clinical and basic research. The information provided in this review will be very useful for further studies to develop novel therapeutic directions for application of pomegranate.

Benzo[a]pyrene Cytotoxicity Tolerance in Testicular Sertoli Cells Involves Aryl-hydrocarbon Receptor and Cytochrome P450 1A1 Expression Deficiencies

Benzo[a]pyrene (B[a]P) is a potent carcinogen and is classified as an endocrine-disrupting chemical. In mammalian testes, Sertoli cells support spermatogenesis. Therefore, if these cells are negatively affected by exposure to xenotoxic chemicals, spermatogenesis can be seriously disrupted. In this context, we evaluated whether mouse testicular TM4 Sertoli cells are susceptible to the induction of cytotoxicity-mediated cell death after exposure to B[a] P in vitro. In the present study, while B[a]P and B[a]P-7,8-diol were not able to induce cell death, exposure to BPDE resulted in cell death. BPDE-induced cell death is accompanied by the activation of caspase-3 and caspase-7. Depolarization of the mitochondrial membrane and cytochrome c release from mitochondria were observed in benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE)-treated cells. These results indicate that TM4 cells are susceptible to apoptosis in a caspase-dependent manner. Western blot and reverse transcription-polymerase chain reaction (RT-PCR) analyses showed that aryl hydrocarbon receptor (AhR) expression was almost undetectable in TM4 cells and that its expression was not altered after B[a]P treatment. This indicates that TM4 cells are nearly AhR-deficient. In TM4 cells, the CYP1A1 protein and its activity were not present. From these results, it is clear that AhR may be a prerequisite for CYP1A1 expression in TM4 cells. Therefore, TM4 cells can be referred to as CYP1A1-deficient cells. Thus, TM4 Sertoli cells are believed to have a rigid and protective cellular machinery against genotoxic agents. In conclusion, it is suggested that tolerance to B[a]P cytotoxicity is associated with insufficient AhR and CYP1A1 expression in testicular Sertoli cells.

Neural-Induced Human Adipose Tissue-Derived Stem Cells Conditioned Medium Ameliorates Rotenone-Induced Toxicity in SH-SY5Y Cells

Parkinson’s disease (PD) is an age-related neurodegenerative disease (NDD) characterized by the degenerative loss of dopaminergic neurons in the substantia nigra along with aggregation of α-synuclein (α-syn). Neurogenic differentiation of human adipose-derived stem cells (NI-hADSCs) by supplementary factors for 14 days activates different biological signaling pathways. In this study, we evaluated the therapeutic role of NI-hADSC-conditioned medium (NI-hADSC-CM) in rotenone (ROT)-induced toxicity in SH-SY5Y cells. Increasing concentrations of ROT led to decreased cell survival at 24 and 48 h in a dose- and time-dependent manner. Treatment of NI-hADSC-CM (50% dilution in DMEM) against ROT (0.5 μM) significantly increased the cell survival. ROT toxicity decreased the expression of tyrosine hydroxylase (TH). Western blot analysis of the Triton X-100-soluble fraction revealed that ROT significantly decreased the oligomeric, dimeric, and monomeric phosphorylated Serine129 (p-S129) α-syn, as well as the total monomeric α-syn expression levels. ROT toxicity increased the oligomeric, but decreased the dimeric and monomeric p-S129 α-syn expression levels. Total α-syn expression (in all forms) was increased in the Triton X-100-insoluble fraction, compared to the control. NI-hADSC-CM treatment enhanced the TH expression, stabilized α-syn monomers, reduced the levels of toxic insoluble p-S129 α-syn, improved the expression of neuronal functional proteins, regulated the Bax/Bcl-2 ratio, and upregulated the expression of pro-caspases, along with PARP-1 inactivation. Moreover, hADSC-CM treatment decreased the cell numbers and have no effect against ROT toxicity on SH-SY5Y cells. The therapeutic effects of NI-hADSC-CM was higher than the beneficial effects of hADSC-CM on cellular signaling. From these results, we conclude that NI-hADSC-CM exerts neuroregenerative effects on ROT-induced PD-like impairments in SH-SY5Y cells.

The intricate biophysical puzzle of caspase-1 activation

This review takes a closer look at the structural components of the molecules involved in the processes leading to caspase-1 activation. Interleukins 1β and 18 (IL-1β, IL-18) are well-known proinflammatory cytokines that are produced following cleavage of their respective precursor proteins by the cysteine protease caspase-1. Active caspase-1 is the final step of the NLRP3 inflammasome, a three-protein intracellular complex involved in inflammation and induction of pyroptosis (a proinflammatory cell-death process). NLRP3 activators facilitate assembly of the inflammasome complex and subsequent activation of caspase-1 by autoproteolysis. However, the definitive structural components of active caspase-1 are still unclear and new data add to the complexity of this process. This review outlines the historical and recent findings that provide supporting evidence for the structural aspects of caspase-1 autoproteolysis and activation.

Liberibacter, A Preemptive Bacterium: Apoptotic Response Repression in the Host Gut at the Early Infection to Facilitate Its Acquisition and Transmission

“Candidatus Liberibacter solanacearum” (Lso) is a phloem-limited Gram-negative bacterium that infects crops worldwide. In North America, two haplotypes of Lso (LsoA and LsoB) are transmitted by the potato psyllid, Bactericera cockerelli (Šulc), in a circulative and persistent manner. Both haplotypes cause damaging plant diseases (e.g., zebra chip in potatoes). The psyllid gut is the first organ Lso encounters and could be a barrier for its transmission. However, little is known about the psyllid gut immune responses triggered upon Lso infection. In this study, we focused on the apoptotic response in the gut of adult potato psyllids at the early stage of Lso infection. We found that there was no evidence of apoptosis induced in the gut of the adult potato psyllids upon infection with either Lso haplotype based on microscopic observations. However, the expression of the inhibitor of apoptosis IAPP5.2 gene (survivin-like) was significantly upregulated during the period that Lso translocated into the gut cells. Interestingly, silencing of IAPP5.2 gene significantly upregulated the expression of two effector caspases and induced apoptosis in the psyllid gut cells. Moreover, RNA interference (RNAi) of IAPP5.2 significantly decreased the Lso titer in the gut of adult psyllids and reduced their transmission efficiency. Taken together, these observations suggest that Lso might repress the apoptotic response in the psyllid guts by inducing the anti-apoptotic gene IAPP5.2 at an early stage of the infection, which may favor Lso acquisition in the gut cells and facilitate its transmission by potato psyllid.

Naringenin exerts anticancer effects by inducing tumor cell death and inhibiting angiogenesis in malignant melanoma

Malignant melanoma is one of the most deadly skin cancer, due to its aggressive proliferation and metastasis. Naringenin, abundantly present in citrus fruits, has widely studied in cancer therapy. In this study, we investigated whether naringenin also has anticancer effects against B16F10 murine and SK-MEL-28 human melanoma cells. Moreover, we assessed the effects of naringenin treatment on angiogenesis of HUVECs and ex vivo sprouting of microvessels.Naringenin inhibited tumor cell proliferation and migration in a dose-dependent manner in B16F10 and SK-MEL-28 cells, which is supported by the results that phosphorylation of ERK1/2 and JNK MAPK decreased. Furthermore, naringenin induced cell apoptosis. Western blot analysisshowed naringenin treatment significantly upregulated the protein expression of activated cas3 and PARP in B16F10 and SK-MEL-28 cells. In addition, in vitro and ex vivo angiogenesis assays demonstrated that naringenin treatment potently suppressed EC migration, tube formation, and sprouting of microvessels. RT-PCR analysis showed that naringenin treatment significantly reduced the mRNA expression of Tie2, but did not inhibit the expression of Ang2. In conclusion, present study demonstrates the anticancer effects of naringenin by its induction of tumor cell death and inhibition of angiogenesis in malignant melanoma, suggesting that naringenin has potential as a safe and effective therapeutic agent to treat melanoma.

The Oscillation Amplitude, Not the Frequency of Cytosolic Calcium, Regulates Apoptosis Induction

Although a rising concentration of cytosolic Ca²⁺ has long been recognized as an essential signal for apoptosis, the dynamical mechanisms by which Ca²⁺ regulates apoptosis are not clear yet. To address this, we constructed a computational model that integrates known biochemical reactions and can reproduce the dynamical behaviors of Ca²⁺-induced apoptosis as observed in experiments. Model analysis shows that oscillating Ca²⁺ signals first convert into gradual signals and eventually transform into a switch-like apoptotic response. Via the two processes, the apoptotic signaling pathway filters the frequency of Ca²⁺ oscillations effectively but instead responds acutely to their amplitude. Collectively, our results suggest that Ca²⁺ regulates apoptosis mainly via oscillation amplitude, rather than frequency, modulation. This study not only provides a comprehensive understanding of how oscillatory Ca²⁺ dynamically regulates the complex apoptotic signaling network but also presents a typical example of how Ca²⁺ controls cellular responses through amplitude modulation.

Role of Inflammasomes in HIV-1 and Drug Abuse Mediated Neuroinflammaging

Despite the effectiveness of combined antiretroviral therapy (cART) in suppressing virus replication, chronic inflammation remains one of the cardinal features intersecting HIV-1, cART, drug abuse, and likely contributes to the accelerated neurocognitive decline and aging in people living with HIV-1 (PLWH) that abuse drugs. It is also estimated that ~30–60% of PLWH on cART develop cognitive deficits associated with HIV-1-associated neurocognitive disorders (HAND), with symptomatology ranging from asymptomatic to mild, neurocognitive impairments. Adding further complexity to HAND is the comorbidity of drug abuse in PLWH involving activated immune responses and the release of neurotoxins, which, in turn, mediate neuroinflammation. Premature or accelerated aging is another feature of drug abusing PLWH on cART regimes. Emerging studies implicate the role of HIV-1/HIV-1 proteins, cART, and abused drugs in altering the inflammasome signaling in the central nervous system (CNS) cells. It is thus likely that exposure of these cells to HIV-1/HIV-1 proteins, cART, and/or abused drugs could have synergistic/additive effects on the activation of inflammasomes, in turn, leading to exacerbated neuroinflammation, ultimately resulting in premature aging referred to as “inflammaging” In this review, we summarize the current knowledge of inflammasome activation, neuroinflammation, and aging in central nervous system (CNS) cells such as microglia, astrocytes, and neurons in the context of HIV-1 and drug abuse.

Melatonin alleviates morphine analgesic tolerance in mice by decreasing NLRP3 inflammasome activation

Morphine is frequently used for pain relief, but long-term morphine therapy in patients with chronic pain results in analgesic tolerance and hyperalgesia. There are no effective therapeutic treatments that limit these detrimental side effects. We found pretreatment with melatonin could decrease morphine-induced analgesic tolerance. There was a significant activation of the NLRP3 inflammasome in the prefrontal cortex and the peripheral blood of morphine-treated mice compared to control animals, which could be blocked by melatonin. The inflammasome activation induced by morphine was mediated by the microglia. SiRNA knockdown or pharmacological inhibition of the NLRP3 abolished the morphine-induced inflammasome activation. Co-administration of melatonin and low-dose morphine had better analgesia effects in the murine models of pain and led to a lower NLRP3 inflammasome activity in brain tissues. Mice deficient for Nlrp3 had a higher nociceptive threshold and were less sensitive to develop morphine-induced analgesic tolerance and acetic acid-induced pain relative to wild-type animals. Concordantly, we observed a significantly elevated level of serum IL-1β, which indicates an increase of NLRP3 inflammasome activity associated with the reduced level of serum melatonin, in heroin-addicted patients relative to healthy individuals. Our results provide a solid basis for conducting a clinical trial with the co-administration of melatonin and morphine for the relief of severe pain.

Structural basis for Ca2+-dependent activation of a plant metacaspase

Plant metacaspases mediate programmed cell death in development, biotic and abiotic stresses, damage-induced immune response, and resistance to pathogen attack. Most metacaspases require Ca²⁺ for their activation and substrate processing. However, the Ca²⁺-dependent activation mechanism remains elusive. Here we report the crystal structures of Metacaspase 4 from Arabidopsis thaliana (AtMC4) that modulates Ca²⁺-dependent, damage-induced plant immune defense. The AtMC4 structure exhibits an inhibitory conformation in which a large linker domain blocks activation and substrate access. In addition, the side chain of Lys225 in the linker domain blocks the active site by sitting directly between two catalytic residues. We show that the activation of AtMC4 and cleavage of its physiological substrate involve multiple cleavages in the linker domain upon activation by Ca²⁺. Our analysis provides insight into the Ca²⁺-dependent activation of AtMC4 and lays the basis for tuning its activity in response to stresses for engineering of more sustainable crops for food and biofuels.

Plant metacaspases mediate immune response following activation by Ca²⁺. Here, via crystallography and functional analyses, the authors show that a linker domain in Arabidopsis Metacaspase 4 blocks substrate access to the active site but is cleaved multiple times in the presence of Ca²⁺ to allow enzyme activation.

Oncoglabrinol C, a new flavan from Oncocalyx glabratus protects endothelial cells against oxidative stress and apoptosis, and modulates hepatic CYP3A4 activity

Active herbal or natural compounds have high chemical diversity and specificity than synthetic drugs. Recently, we have validated the hypoglycemic salutation of Oncocalyx glabratus in rodent model, and demonstrated the activation of PPARα/γ by its newly ioslated flavan derivative Oncoglabrinol C (5,3′-Dihydroxyflavan 7-4′-O-digallate) in liver cells (HepG2). Here we evaluated the potential of Oncoglabrinol C against Dichlorofluorescin (DCFH) and Methylglyoxal (MGO) induced endothelial cells (HUVEC) oxidative and apoptotic damage, including activation of PXR-mediated hepatic CYP3A4. Our MTT assay showed protection of ~57% and ~63.5% HUVEC cells by 10 and 20 μg/ml doses of Oncoglabrinol C, respectively through attenuating DCFH triggered free-radicals. Also, the two doses effectively protected ~53% and ~65.5% cells, respectively by reversing MGO toxicity. In DCFH and MGO treated cells, Oncoglabrinol C (20 μg/ml) effectively downregulated caspase 3/7 activity by ~33% and ~43.5%, respectively. Moreover, in reporter gene (dual-luciferase) assay, Oncoglabrinol C (20 μg/ml) moderately activated hepatic CYP3A4. Molecular docking of Oncoglabrinol C indicated its strong interactions with cellular caspase 3/7, PPARα/γ and PXR proteins, which supported its anti-apoptotic (antagonistic) as well as pro-hypoglycemic and PXR/CYP activating (agonistic) activities. Taken together, our findings demonstrated the potential of Oncoglabrinol C in reversing the endothelial oxidative and apoptotic damage as well as in the activation of hepatic CYP3A4. This warrants further evaluations of Oncoglabrinol C and related compounds towards developing effective and safe drugs against diabetes associated cardiovascular disorders.

Protease propeptide structures, mechanisms of activation, and functions

Proteases are a diverse group of hydrolytic enzymes, ranging from single-domain catalytic molecules to sophisticated multi-functional macromolecules. Human proteases are divided into five mechanistic classes: aspartate, cysteine, metallo, serine and threonine proteases, based on the catalytic mechanism of hydrolysis. As a protective mechanism against uncontrolled proteolysis, proteases are often produced and secreted as inactive precursors, called zymogens, containing inhibitory N-terminal propeptides. Protease propeptide structures vary considerably in length, ranging from dipeptides and propeptides of about 10 amino acids to complex multifunctional prodomains with hundreds of residues. Interestingly, sequence analysis of the different protease domains has demonstrated that propeptide sequences present higher heterogeneity compared with their catalytic domains. Therefore, we suggest that protease inhibition targeting propeptides might be more specific and have less off-target effects than classical inhibitors. The roles of propeptides, besides keeping protease latency, include correct folding of proteases, compartmentalization, liganding, and functional modulation. Changes in the propeptide sequence, thus, have a tremendous impact on the cognate enzymes. Small modifications of the propeptide sequences modulate the activity of the enzymes, which may be useful as a therapeutic strategy. This review provides an overview of known human proteases, with a focus on the role of their propeptides. We review propeptide functions, activation mechanisms, and possible therapeutic applications.

Caspase-8: The double-edged sword

Caspase-8 is a cysteine - aspartate specific protease that classically triggers the extrinsic apoptotic pathway, in response to the activation of cell surface Death Receptors (DRs) like FAS, TRAIL-R and TNF-R. Besides it's roles in triggering death receptor-mediated apoptosis, Caspase-8 has also been implicated in the onsets of anoikis, autophagy and pyroptosis. Furthermore, Caspase-8 also plays a crucial pro-survival function by inhibiting an alternative form of programmed cell death called necroptosis. Low expression levels of pro-Caspase-8 is therefore associated with the malignant transformation of cancers. However, the long-held notion that pro-Caspase-8 expression/activity is generally lost in most cancers, thereby contributing to apoptotic escape and enhanced resistance to anti-cancer therapeutics, has been found to be true for only a minority of cancers types. In the majority of cases, pro-Caspase-8 expression is maintained and sometimes elevated, while it's apoptotic activity is regulated through different mechanisms. This supports the notion that the non-apoptotic functions of Caspase-8 offer growth advantage in these cancer types and have, therefore, gained renewed interest in the recent years. In light of these reasons, a number of therapeutic approaches have been employed, with the intent of targeting pro-Caspase-8 in cancer cells. In this review, we would attempt to discuss - the classic roles of Caspase-8 in initiating apoptosis; it's non-apoptotic functions; it's the clinical significance in different cancer types; and the therapeutic applications exploiting the ability of pro-Caspase-8 to regulate various cellular functions.

Structural Mechanism for GSDMD Targeting by Autoprocessed Caspases in Pyroptosis

The pyroptosis execution protein GSDMD is cleaved by inflammasome-activated caspase-1 and LPS-activated caspase-11/4/5. The cleavage unmasks the pore-forming domain from GSDMD-C-terminal domain. How the caspases recognize GSDMD and its connection with caspase activation are unknown. Here, we show site-specific caspase-4/11 autoprocessing, generating a p10 product, is required and sufficient for cleaving GSDMD and inducing pyroptosis. The p10-form autoprocessed caspase-4/11 binds the GSDMD-C domain with a high affinity. Structural comparison of autoprocessed and unprocessed capase-11 identifies a β sheet induced by the autoprocessing. In caspase-4/11-GSDMD-C complex crystal structures, the β sheet organizes a hydrophobic GSDMD-binding interface that is only possible for p10-form caspase-4/11. The binding promotes dimerization-mediated caspase activation, rendering a cleavage independently of the cleavage-site tetrapeptide sequence. Crystal structure of caspase-1-GSDMD-C complex shows a similar GSDMD-recognition mode. Our study reveals an unprecedented substrate-targeting mechanism for caspases. The hydrophobic interface suggests an additional space for developing inhibitors specific for pyroptotic caspases.

Caspases in Cell Death, Inflammation, and Pyroptosis

Caspases are a family of conserved cysteine proteases that play key roles in programmed cell death and inflammation. In multicellular organisms, caspases are activated via macromolecular signaling complexes that bring inactive procaspases together and promote their proximity-induced autoactivation and proteolytic processing. Activation of caspases ultimately results in programmed execution of cell death, and the nature of this cell death is determined by the specific caspases involved. Pioneering new research has unraveled distinct roles and cross talk of caspases in the regulation of programmed cell death, inflammation, and innate immune responses. In-depth understanding of these mechanisms is essential to foster the development of precise therapeutic targets to treat autoinflammatory disorders, infectious diseases, and cancer. This review focuses on mechanisms governing caspase activation and programmed cell death with special emphasis on the recent progress in caspase cross talk and caspase-driven gasdermin D-induced pyroptosis.

A Cell's Fate: An Overview of the Molecular Biology and Genetics of Apoptosis

Apoptosis is one of the main types of regulated cell death, a complex process that can be triggered by external or internal stimuli, which activate the extrinsic or the intrinsic pathway, respectively. Among various factors involved in apoptosis, several genes and their interactive networks are crucial regulators of the outcomes of each apoptotic phase. Furthermore, mitochondria are key players in determining the way by which cells will react to internal stress stimuli, thus being the main contributor of the intrinsic pathway, in addition to providing energy for the whole process. Other factors that have been reported as important players of this intricate molecular network are miRNAs, which regulate the genes involved in the apoptotic process. Imbalance in any of these mechanisms can lead to the development of several illnesses, hence, an overall understanding of these processes is essential for the comprehension of such situations. Although apoptosis has been widely studied, the current literature lacks an updated and more general overview on this subject. Therefore, here, we review and discuss the mechanisms of apoptosis, highlighting the roles of genes, miRNAs, and mitochondria involved in this type of cell death.