Protective role of new nitrogen compounds on ROS/RNS-mediated damage to PC12 cells

Nrf2: a dark horse in doxorubicin-induced cardiotoxicity

Being a broad-spectrum anticancer drug, doxorubicin is indispensable for clinical treatment. Unexpectedly, its cardiotoxic side effects have proven to be a formidable obstacle. Numerous studies are currently devoted to elucidating the pathological mechanisms underlying doxorubicin-induced cardiotoxicity. Nrf2 has always played a crucial role in oxidative stress, but numerous studies have demonstrated that it also plays a vital part in pathological mechanisms like cell death and inflammation. Numerous studies on the pathological mechanisms associated with doxorubicin-induced cardiotoxicity demonstrate this. Several clinical drugs, natural and synthetic compounds, as well as small molecule RNAs have been demonstrated to prevent doxorubicin-induced cardiotoxicity by activating Nrf2. Consequently, this study emphasizes the introduction of Nrf2, discusses the role of Nrf2 in doxorubicin-induced cardiotoxicity, and concludes with a summary of the therapeutic modalities targeting Nrf2 to ameliorate doxorubicin-induced cardiotoxicity, highlighting the potential value of Nrf2 in doxorubicin-induced cardiotoxicity.

Synergistic integration of dihydro-artemisinin with γ-aminobutyric acid results in a more potential anti-depressant

Three hybrids of dihydro-artemisinin (DHA) with β-aminopropionic acid, γ-aminobutyric acid, and histamine have been designed and synthesized. The conjugate of DHA with GABA labelled as 5b was confirmed the most active candidate against both Cort- and SNP-induced PC12 cell impairments with EC₅₀ value of 8.04 ± 0.35, and 9.38 ± 0.56 μM, respectively. 5b was clearly highlighted as a good modulator on protein expression of Akt, Bcl-2, and Bax, indicating its functions against programmed cell apoptosis. 5b significantly reversed the Cort-induced excessive calcium influx and release from internal organelles. It was demonstrated the ability to express increased levels of β-tubulin III and to up-regulate phosphorylation level of cAMP response element-binding protein (CREB), leading to cell differentiation. It can penetrate blood - brain barrier (BBB) with propriate stability. Altogether, these data strongly support that 5b is a potential anti-depressant.

Metabolic disparities of different oxidative stress‑inducing conditions in HTR8/SVneo cells

Placental oxidative stress is present throughout the duration of pregnancy, but it is when oxidative stress exceeds the normal physiological level that complications can occur. Trophoblast cell lines are commonly utilized for oxidative stress research due to their distinct uniform cell population and easy-to-apply interventions. However, conflicting results are often reported when different oxidative stress cell models are used. In this study, the aim was to characterize the intracellular and extracellular metabolite profiles of different oxidative stress cell models commonly used in the research of pregnancy complications. HTR8/SVneo human trophoblast cell lines were treated with five different oxidative stress-inducing conditions: Hypoxia (1% oxygen); hypoxia and reoxygenation; cobalt chloride (CoCl₂; 300 µmol/l); sodium nitroprusside (SNP; 2.5 mmol/l); and the serum of women with preeclampsia (10% v/v). Intracellular metabolites were extracted from cells and extracellular metabolites were collected from spent media for metabolomic analysis via gas chromatography-mass spectrometry. The results demonstrated that there were distinct differences in the intracellular and extracellular metabolome between the different cell models. Meanwhile, treatments with exogenous drugs, such as CoCl₂ and SNP, resulted in more similar metabolite profiles. These disparities between the different oxidative stress cell models will have implications for the applications of these results, and highlight the need for the standardization of oxidative stress cell models in obstetric research.

Artemisinin conferred ERK mediated neuroprotection to PC12 cells and cortical neurons exposed to sodium nitroprusside-induced oxidative insult

The production of nitric oxide (NO) is one of the primary mediators of ischemic damage, glutamate neurotoxicity and neurodegeneration and therefore inhibition of NO-induced neurotoxicity may be considered a therapeutic target for reducing neuronal cell death (neuroprotection). In this study, artemisinin, a well-known anti-malaria drug was found to suppress sodium nitroprusside (SNP, a nitric oxide donor)-induced cell death in the PC12 cells and brain primary cortical neuronal cultures. Pretreatment of PC12 cells with artemisinin significantly suppressed SNP-induced cell death by decreasing the extent of oxidation, preventing the decline of mitochondrial membrane potential, restoring abnormal changes in nuclear morphology and reducing lactate dehydrogenase release and inhibiting caspase 3/7 activities. Western blotting analysis revealed that artemisinin was able to activate extracellular regulated protein kinases (ERK) pathway. Furthermore, the ERK inhibitor PD98059 blocked the neuroprotective effect of artemisinin whereas the PI3K inhibitor LY294002 had no effect. Cumulatively these findings support the notion that artemisinin confers neuroprotection from SNP-induce neuronal cell death insult, a phenomenon coincidentally related to activation of ERK phosphorylation. This SNP-induced oxidative insult in PC12 cell culture model may be useful to investigate molecular mechanisms of NO-induced neurotoxicity and drug-induced neuroprotection, and to generate novel therapeutic concepts for ischemic disease treatment.

Delivery of LLKKK18 loaded into self-assembling hyaluronic acid nanogel for tuberculosis treatment

Tuberculosis (TB), a disease caused by the human pathogen Mycobacterium tuberculosis, recently joined HIV/AIDS on the top rank of deadliest infectious diseases. Low patient compliance due to the expensive, long-lasting and multi-drug standard therapies often results in treatment failure and emergence of multi-drug resistant strains. In this scope, antimicrobial peptides (AMPs) arise as promising candidates for TB treatment. Here we describe the ability of the exogenous AMP LLKKK18 to efficiently kill mycobacteria. The peptide's potential was boosted by loading into self-assembling Hyaluronic Acid (HA) nanogels. These provide increased stability, reduced cytotoxicity and degradability, while potentiating peptide targeting to main sites of infection. The nanogels were effectively internalized by macrophages and the peptide presence and co-localization with mycobacteria within host cells was confirmed. This resulted in a significant reduction of the mycobacterial load in macrophages infected in vitro with the opportunistic M. avium or the pathogenic M. tuberculosis, an effect accompanied by lowered pro-inflammatory cytokine levels (IL-6 and TNF-α). Remarkably, intra-tracheal administration of peptide-loaded nanogels significantly reduced infection levels in mice infected with M. avium or M. tuberculosis, after just 5 or 10 every other day administrations. Considering the reported low probability of resistance acquisition, these findings suggest a great potential of LLKKK18-loaded nanogels for TB therapeutics.

Rutin, A Natural Flavonoid Protects PC12 Cells Against Sodium Nitroprusside-Induced Neurotoxicity Through Activating PI3K/Akt/mTOR and ERK1/2 Pathway

Free radicals induced neural damage is implicated in CNS diseases and rutin isolated form Lonicera japonica are reported to have neuroprotective activity. Previously, we confirmed that rutin exerted neuroprotective effect against sodium nitroprusside (SNP)-induced cell death in PC12 cells. However, the neuroprotective mechanism of rutin is still not fully uncovered. Here, we found that rutin significantly decreased SNP-induced reactive oxygen species in PC12 cells. Rutin reversed the declined GSH/GSSG ratio and mitochondrial membrane potential induced by SNP. Moreover, rutin activated both the protein Akt/mTOR and the extracellular signal-regulated kinase (ERK1/2) signaling pathways and the neuroprotective effects of rutin were blocked by either the specific PI3K inhibitor LY294002 or the MAPK pathway inhibitor PD98059. In summary, these results demonstrated that the neuroprotective effects of rutin might be through activating both the PI3K/Akt/mTOR and ERK1/2 signaling pathways. Our findings support that rutin may have therapeutic potential for the treatment of CNS diseases related to NO neurotoxicity.

Redox regulation of NLRP3 inflammasomes: ROS as trigger or effector?

SIGNIFICANCE

Inflammasomes are multiprotein complexes localized within the cytoplasm of the cell that are responsible for the maturation of proinflammatory cytokines such as interleukin-1β (IL-1β) and IL-18, and the activation of a highly inflammatory form of cell death, pyroptosis. In response to infection or cellular stress, inflammasomes are assembled, activated, and involved in host defense and pathophysiology of diseases. Clarification of the molecular mechanisms leading to the activation of this intracellular inflammatory machinery may provide new insights into the concept of inflammation as the root of and route to human diseases.

RECENT ADVANCES

The activation of inflammasomes, specifically the most fully characterized inflammasome-the nucleotide-binding oligomerization domain (NOD)-like receptor containing pyrin domain 3 (NLRP3) inflammasome, is now emerging as a critical molecular mechanism for many degenerative diseases. Several models have been developed to describe how NLRP3 inflammasomes are activated, including K(+) efflux, lysosome function, endoplasmic reticulum (ER) stress, intracellular calcium, ubiquitination, microRNAs, and, in particular, reactive oxygen species (ROS).

CRITICAL ISSUES

ROS may serve as a "kindling" or triggering factor to activate NLRP3 inflammasomes as well as "bonfire" or "effector" molecules, resulting in pathological processes. Increasing evidence seeks to understand how this spatiotemporal action of ROS occurs during NLRP3 inflammasome activation, which will be a major focus of this review.

FUTURE DIRECTIONS

It is imperative to know how this dual action of ROS works during NLRP3 inflammation activation on different stimuli and what relevance such spatiotemporal redox regulation of NLRP3 inflammasomes has in cell or organ functions and possible human diseases.

Neuroprotective effect of 2-(4-methoxyphenyl)ethyl-2-acetamido-2-deoxy-β-D-pyranoside against sodium nitroprusside-induced neurotoxicity in HT22 cells

2-(4-Methoxyphenyl) ethyl-2-acetamido-2-deoxy-β-D-pyranoside (GlcNAc-Sal), the salidroside analog was synthesized and shown to inhibit hypoglycemia and serum limitation induced apoptosis in PC12 cells. This study investigated the protective effects of GlcNAc-Sal on sodium nitroprusside (SNP)-induced cytotoxicity in HT22 cells. Cell viability tests and Hoechst 33342 staining comfirmed that GlcNAc-Sal pretreatment attenuated SNP-stimulated apoptotic cell death in HT22 cells in a concentration-dependent manner. The measurements of reactive oxygen species (ROS), nitric oxide (NO) production and apoptosis-related gene and protein expression suggest that the protection of GlcNAc-Sal, shown in this study, might be mediated by inhibiting intracellular ROS and NO production, and regulating apoptosis-related gene and protein expression during SNP stimulation. Perhaps, this study might contribute to the development of GlcNAc-Sal as an agent for preventing and/or treating a variety of NO-induced brain diseases.

Claulansine F suppresses apoptosis induced by sodium nitroprusside in PC12 cells

Reactive oxygen species (ROS) are known to be involved in many neurodegenerative diseases. This study assessed the effect of Claulansine F, a new carbazole isolated from Clausena lansium, on sodium nitroprusside (SNP)-treated rat pheochromocytoma PC12 cells. First, it was found that Claulansine F showed more potential on inhibiting the programmed death of PC12 cells than edaravone by cell viability, morphologic observation, and flow cytometric analysis. Further results also showed that Claulansine F attenuated the production of total intracellular ROS formation and lipid peroxidation in PC12 cells, inhibited the mitochondrial membrane potential (MMP) loss, and prevented the programmed cell death event via the P53/Bcl-2 family pathway. Its protective effect was likely medicated by the hydroxyl radical (·OH) scavenging ability, as it appeared to be not involved in the natural antioxidant system. These results suggested a promising potential for Claulansine F as a ROS scavenger in pathologies, where an oxidative stress is involved.

Cryptotanshinone from Salviae miltiorrhizae radix inhibits sodium-nitroprusside-induced apoptosis in neuro-2a cells

The root of Salvia miltiorrhiza (Salviae miltiorrhizae radix), a herbal medicine has widely been used for the treatment of pain, miscarriage and oedema. In this study, we evaluated the neuroprotective effect of cryptotanshinone (CRT) from Salviae miltiorrhizae radix on sodium-nitroprusside (SNP)-induced apoptosis in neuro-2a (N2a) cells, and further investigated its action mechanism in signalling pathways. The effects of CRT against SNP-induced toxicity, mitochondrial membrane potential (MMP) changes, and oxidants/antioxidant defences and apoptotic signalling pathways were investigated in N2a cells. Cryptotanshinone significantly inhibited SNP-induced cell toxicity and the generation of reactive oxygen and nitrogen species (RONS), and improved MMP in N2a cells. Cryptotanshinone significantly suppressed SNP-induced peroxidation of lipid and protein, and the expression of Gclc mRNA. In the signalling pathway, CRT effectively blocked SNP-induced activation of NF-κB and ERK1/2 and JNK MAPK pathways through the elevation of Akt and cyclic AMP response element binding protein. Furthermore, CRT remarkably reduced the increase of mitochondrial Bax/Bcl-2 ratio, the release of cytochrome c from mitochondria to cytosol, and the activations of cytosolic procaspase-3 and nuclear inactive poly ADP (adenosine diphosphate)-ribose polymerase by SNP-induced apoptosis. These results indicate that CRT has neuroprotective effects against SNP-induced apoptosis in neuronal cells via the regulation of mitochondrial apoptotic cascades and antiapoptotic cellular signalling pathways.

Lipid raft redox signaling: molecular mechanisms in health and disease

Lipid rafts, the sphingolipid and cholesterol-enriched membrane microdomains, are able to form different membrane macrodomains or platforms upon stimulations, including redox signaling platforms, which serve as a critical signaling mechanism to mediate or regulate cellular activities or functions. In particular, this raft platform formation provides an important driving force for the assembling of NADPH oxidase subunits and the recruitment of other related receptors, effectors, and regulatory components, resulting, in turn, in the activation of NADPH oxidase and downstream redox regulation of cell functions. This comprehensive review attempts to summarize all basic and advanced information about the formation, regulation, and functions of lipid raft redox signaling platforms as well as their physiological and pathophysiological relevance. Several molecular mechanisms involving the formation of lipid raft redox signaling platforms and the related therapeutic strategies targeting them are discussed. It is hoped that all information and thoughts included in this review could provide more comprehensive insights into the understanding of lipid raft redox signaling, in particular, of their molecular mechanisms, spatial-temporal regulations, and physiological, pathophysiological relevances to human health and diseases.

Protective effects of polyphenolic compounds on oxidative stress-induced cytotoxicity in PC12 cells

To investigate the beneficial properties associated with polyphenols, we screened 12 polyphenols for their ability to increase the viability of PC12 cells subjected to oxidative stress via CoCl2 and H2O2. Cell viability data demonstrate that 50 micromol/L methyl gallate and 50 micromol/L fisetin significantly increase viability of H2O2-stressed cells. Further, viability data suggest that 100 micromol/L epigallocatechin gallate (EGCG) increases basal viability, but has no rescue effect on cells stressed with CoCl2 or H2O2. Analysis of intracellular reactive oxygen species (ROS) shows that EGCG, methyl gallate, and gallic acid are effective in reducing CoCl2-derived ROS, and that methyl gallate is effective in attenuating H2O2-derived ROS. Examination of nitric oxide concentrations shows that methyl gallate significantly increases nitric oxide, both in nonstressed and H2O2-stressed cells, whereas EGCG results are consistent with the scavenging of nitric oxide under nonstressed and stressed conditions. Furthermore, analysis of total glutathione levels reveals that EGCG, methyl gallate, and gallic acid pretreatments with and without H2O2 stress have the ability to significantly alter glutathione metabolism. These findings suggest that EGCG, methyl gallate, and gallic acid may have potential therapeutic properties.

Octyl Gallate Inhibits ATP-induced Intracellular Calcium Increase in PC12 Cells by Inhibiting Multiple Pathways

Phenolic compounds affect intracellular free Ca(2+) concentration ([Ca(2+)](i)) signaling. The study examined whether the simple phenolic compound octyl gallate affects ATP-induced Ca(2+) signaling in PC12 cells using fura-2-based digital Ca(2+) imaging and whole-cell patch clamping. Treatment with ATP (100 microM) for 90 s induced increases in [Ca(2+)](i) in PC12 cells. Pretreatment with octyl gallate (100 nM to 20 microM) for 10 min inhibited the ATP-induced [Ca(2+)](i) response in a concentration-dependent manner (IC(50)=2.84 microM). Treatment with octyl gallate (3 microM) for 10 min significantly inhibited the ATP-induced response following the removal of extracellular Ca(2+) with nominally Ca(2+)-free HEPES HBSS or depletion of intracellular Ca(2+) stores with thapsigargin (1 microM). Treatment for 10 min with the L-type Ca(2+) channel antagonist nimodipine (1 microM) significantly inhibited the ATP-induced [Ca(2+)](i) increase, and treatment with octyl gallate further inhibited the ATP-induced response. Treatment with octyl gallate significantly inhibited the [Ca(2+)](i) increase induced by 50 mM KCl. Pretreatment with protein kinase C inhibitors staurosporin (100 nM) and GF109203X (300 nM), or the tyrosine kinase inhibitor genistein (50 microM) did not significantly affect the inhibitory effects of octyl gallate on the ATP-induced response. Treatment with octyl gallate markedly inhibited the ATP-induced currents. Therefore, we conclude that octyl gallate inhibits ATP-induced [Ca(2+)](i) increase in PC12 cells by inhibiting both non-selective P2X receptor-mediated influx of Ca(2+) from extracellular space and P2Y receptor-induced release of Ca(2+) from intracellular stores in protein kinase-independent manner. In addition, octyl gallate inhibits the ATP-induced Ca(2+) responses by inhibiting the secondary activation of voltage-gated Ca(2+) channels.

Oxidative DNA damage protection and repair by polyphenolic compounds in PC12 cells

Biological systems are frequently exposed to excessive reactive oxygen species, causing a disturbance in the cells natural antioxidant defence systems and resulting in damage to all biomolecules, including nucleic acids. In fact, oxidative DNA damage is described as the type of damage most likely to occur in neuronal cells. In this study, three polyphenolic compounds, luteolin, quercetin and rosmarinic acid, were investigated for their protective effects against oxidative DNA damage induced in PC12 cells, a neuronal cell model. Although luteolin and quercetin prevented the formation of strand breaks to a greater extent than rosmarinic acid, this last one presented the highest capacity to repair strand breaks formation. In addition, rosmarinic acid was the only compound tested that increased the repair of oxidized nucleotidic bases induced with the photosensitizer compound [R]-1-[(10-chloro-4-oxo-3-phenyl-4H-benzo[a]quinolizin-1-yl) carbonyl]-2-pyrrolidine-methanol (Ro 19-8022). The activity of repair enzymes was indicated by the in vitro base excision repair assay, using a cell-free extract obtained from cells previously treated with the compounds to incise DNA. The protective effect of rosmarinic acid was further confirmed by the increased expression of OGG1 repair gene, observed through real time RT-PCR. The data obtained is indicative that rosmarinic acid seems to act on the intracellular mechanisms responsible for DNA repair, rather than by a direct effect on reactive oxygen species scavenging, as deducted from the effects observed for luteolin and quercetin. Therefore, these results suggest the importance of these polyphenols, and in particular rosmarinic acid, as protectors of oxidative stress-induced DNA damage that commonly occurs in several pathological conditions, such as neurodegenerative diseases.