Regulated production of free radicals by the mitochondrial electron transport chain: Cardiac ischemic preconditioning

Label-Free Assessment of Key Biological Autofluorophores: Material Characteristics and Opportunities for Clinical Applications

Autofluorophores are endogenous fluorescent compounds that naturally occur in the intra and extracellular spaces of all tissues and organs. Most have vital biological functions - like the metabolic cofactors NAD(P)H and FAD+, as well as the structural protein collagen. Others are considered to be waste products - like lipofuscin and advanced glycation end products - which accumulate with age and are associated with cellular dysfunction. Due to their natural fluorescence, these materials have great utility for enabling non-invasive, label-free assays with direct ties to biological function. Numerous technologies, with different advantages and drawbacks, are applied to their assessment, including fluorescence lifetime imaging microscopy, hyperspectral microscopy, and flow cytometry. Here, the applications of label-free autofluorophore assessment are reviewed for clinical and health-research applications, with specific attention to biomaterials, disease detection, surgical guidance, treatment monitoring, and tissue assessment - fields that greatly benefit from non-invasive methodologies capable of continuous, in vivo characterization.

The ε-Isozyme of Protein Kinase C (PKCε) Is Impaired in ALS Motor Cortex and Its Pulse Activation by Bryostatin-1 Produces Long Term Survival in Degenerating SOD1-G93A Motor Neuron-like Cells

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive and ultimately fatal neurodegenerative disease, characterized by a progressive depletion of upper and lower motor neurons (MNs) in the brain and spinal cord. The aberrant regulation of several PKC-mediated signal transduction pathways in ALS has been characterized so far, describing either impaired expression or altered activity of single PKC isozymes (α, β, ζ and δ). Here, we detailed the distribution and cellular localization of the ε-isozyme of protein kinase C (PKCε) in human postmortem motor cortex specimens and reported a significant decrease in both PKCε mRNA (PRKCE) and protein immunoreactivity in a subset of sporadic ALS patients. We furthermore investigated the steady-state levels of both pan and phosphorylated PKCε in doxycycline-activated NSC-34 cell lines carrying the human wild-type (WT) or mutant G93A SOD1 and the biological long-term effect of its transient agonism by Bryostatin-1. The G93A-SOD1 cells showed a significant reduction of the phosphoPKCε/panPKCε ratio compared to the WT. Moreover, a brief pulse activation of PKCε by Bryostatin-1 produced long-term survival in activated G93A-SOD1 degenerating cells in two different cell death paradigms (serum starvation and chemokines-induced toxicity). Altogether, the data support the implication of PKCε in ALS pathophysiology and suggests its pharmacological modulation as a potential neuroprotective strategy, at least in a subgroup of sporadic ALS patients.

Cotton Fiber Development Requires the Pentatricopeptide Repeat Protein GhIm for Splicing of Mitochondrial nad7 mRNA

Pentatricopeptide repeat (PPR) proteins encoded by nuclear genomes can bind to organellar RNA and are involved in the regulation of RNA metabolism. However, the functions of many PPR proteins remain unknown in plants, especially in polyploidy crops. Here, through a map-based cloning strategy and Clustered regularly interspaced short palindromic repeats/cas9 (CRISPR/cas9) gene editing technology, we cloned and verified an allotetraploid cotton immature fiber (im) mutant gene (GhImA) encoding a PPR protein in chromosome A03, that is associated with the non-fluffy fiber phenotype. GhImA protein targeted mitochondrion and could bind to mitochondrial nad7 mRNA, which encodes the NAD7 subunit of Complex I. GhImA and its homolog GhImD had the same function and were dosage-dependent. GhImA in the im mutant was a null allele with a 22 bp deletion in the coding region. Null GhImA resulted in the insufficient GhIm dosage, affected mitochondrial nad7 pre-mRNA splicing, produced less mature nad7 transcripts, and eventually reduced Complex I activities, up-regulated alternative oxidase metabolism, caused reactive oxygen species (ROS) burst and activation of stress or hormone response processes. This study indicates that the GhIm protein participates in mitochondrial nad7 splicing, affects respiratory metabolism, and further regulates cotton fiber development via ATP supply and ROS balance.

A Review on Free Radicals and Antioxidants

Free radicals are generated in our body by several systems. A balance among free radicals and antioxidants is an important matter for appropriate physiological function. If free radicals become greater than the ability of the body to control them, a case known as oxidative stress appears, as a result of that, a number of human diseases spread in the body. Antioxidants can contribute to facingthis oxidative stress. The present review provides a brief overview of free radicals, oxidative stress, some natural antioxidants and the relationship between them.

Mitochondrial regulation of cardiac aging

Aging is associated with progressive decline in cardiac structure and function. Accumulating evidence in model organisms and humans links cardiac aging to mitochondrial regulation, encompassing a complex interplay of mitochondrial morphology, mitochondrial ROS, mitochondrial DNA mutations, mitochondrial unfolded protein response, nicotinamide adenine dinucleotide levels and sirtuins, as well as mitophagy. This review summarizes the recent discoveries on the mitochondrial regulation of cardiac aging and the possible molecular mechanisms underlying the anti-aging effects, as well as the potential interventions that alleviate aging-related cardiac diseases and attenuate cardiac aging via the regulation of mitochondria.

Possible role of mitochondrial K-ATP channel and nitric oxide in protection of the neonatal rat heart

Cardioprotective effect of ischemic preconditioning (IPC) and ischemic postconditioning (IPoC) in adult hearts is mediated by mitochondrial-K-ATP channels and nitric oxide (NO). During early developmental period, rat hearts exhibit higher resistance to ischemia–reperfusion (I/R) injury and their resistance cannot be further increased by IPC or IPoC. Therefore, we have speculated, whether mechanisms responsible for high resistance of neonatal heart may be similar to those of IPC and IPoC. To test this hypothesis, rat hearts isolated on days 1, 4, 7, and 10 of postnatal life were perfused according to Langendorff. Developed force (DF) of contraction was measured. Hearts were exposed to 40 min of global ischemia followed by reperfusion up to the maximum recovery of DF. IPoC was induced by 5 cycles of 10-s ischemia. Mito-K-ATP blocker (5-HD) was administered 5 min before ischemia and during first 20 min of reperfusion. Another group of hearts was isolated for biochemical analysis of 3-nitrotyrosine, and serum samples were taken to measure nitrate levels. Tolerance to ischemia did not change from day 1 to day 4 but decreased on days 7 and 10. 5-HD had no effect either on neonatal resistance to I/R injury or on cardioprotective effect of IPoC on day 10. Significant difference was found in serum nitrate levels between days 1 and 10 but not in tissue 3-nitrotyrosine content. It can be concluded that while there appears to be significant difference of NO production, mito-K-ATP and ROS probably do not play role in the high neonatal resistance to I/R injury.

Constitutive downregulation protein kinase C epsilon in hSOD1G93A astrocytes influences mGluR5 signaling and the regulation of glutamate uptake

Accumulating evidence indicates that motor neuron degeneration in amyotrophic lateral sclerosis (ALS) is a non-cell-autonomous process and that impaired glutamate clearance by astrocytes, leading to excitotoxicity, could participate in progression of the disease. In astrocytes derived from an animal model of ALS (hSOD1^G93A rats), activation of type 5 metabotropic glutamate receptor (mGluR5) fails to increase glutamate uptake, impeding a putative dynamic neuroprotective mechanism involving astrocytes. Using astrocyte cultures from hSOD1^G93A rats, we have demonstrated that the typical Ca²⁺ oscillations associated with mGluR5 activation were reduced, and that the majority of cells responded with a sustained elevation of intracellular Ca²⁺ concentration. Since the expression of protein kinase C epsilon isoform (PKCɛ) has been found to be considerably reduced in astrocytes from hSOD1^G93A rats, the consequences of manipulating its activity and expression on mGluR5 signaling and on the regulation of glutamate uptake have been examined. Increasing PKCɛ expression was found to restore Ca²⁺ oscillations induced by mGluR5 activation in hSOD1^G93A -expressing astrocytes. This was also associated with an increase in glutamate uptake capacity in response to mGluR5 activation. Conversely, reducing PKCɛ expression in astrocytes from wild-type animals with specific PKCɛ-shRNAs was found to alter the mGluR5 associated oscillatory signaling profile, and consistently reduced the regulation of the glutamate uptake-mediated by mGluR5 activation. These results suggest that PKCɛ is required to generate Ca²⁺ oscillations following mGluR5 activation, which support the regulation of astrocytic glutamate uptake. Reduced expression of astrocytic PKCɛ could impair this neuroprotective process and participate in the progression of ALS.

Kidney remote ischemic preconditioning as a novel strategy to explore the accurate protective mechanisms underlying remote ischemic preconditioning

INTRODUCTION

This study reports a novel strategy for investigating the key factors responsible for the protective effect of remote ischemic preconditioning (RIPC) against renal ischemia-reperfusion (IR) injury, which remains the leading cause of the acute kidney injury that increase the morbidity and mortality in patients with renal impairment.

METHODS

The renal blood flow of the right kidneys in kidney remote ischemic preconditioning (KRIPC) group was occluded for 20 min. After 48 h, the renal blood flow of the left kidneys of both KRIPC and IPC groups was occluded for 30 min, and mice were dissected after 7 days of the last surgery. Blood samples were analyzed by an animal blood counter. The levels of creatinine, urea nitrogen, lipid peroxidation, nitric oxide (NO), and high-density lipoproteins (HDLs) were estimated in the plasma of mice. Kidney slices were stained with 2% triphenyltetrazolium chloride (TTC) to estimate the renal infarction.

RESULTS

Unlike KRIPC group, data from IPC group revealed a massive reduction in neutrophils count, a significant increase in creatinine, urea nitrogen, and HDLs levels, and an increase in the renal infarction compared with control group.

CONCLUSION

This is the first study demonstrating KRIPC as a novel and applicable model with the goal of defining the accurate protective mechanisms underlying RIPC against IR injury.

Cognitive Impairment Associated with Parkinson's Disease: Role of Mitochondria

Parkinson's disease (PD) is a movement disorder and is associated with some of the intellectual disabilities like cognitive dysfunctions. PD associated cognitive dysfunctions have been proved well in both preclinical and clinical set ups. Like other neurodegenerative diseases, insults to mitochondria have a significant role in the pathobiology of PD associated dementia (PDD). Neurotoxins like MPTP, mutations of the mitochondrial genes, oxidative stress, imbalanced redox mechanisms and dysregulated mitochondrial dynamics have been implicated in mitochondrial dysfunctions and have paramount importance in the pathobiology of PDD. However, the extent of contribution of mitochondrial dysfunctions towards cognitive deficits in PD has not been characterized completely. In this review we highlight on the contribution of mitochondrial dysfunction to PDD. We also highlight different behavioural tests used in nonhuman primate and rodent models for assessing cognitive deficits and some common techniques for evaluation of mitochondrial dysfunction in PDD.

Mitochondrial dysfunction as a central event for mechanisms underlying insulin resistance: the roles of long chain fatty acids

Insulin resistance is characterized by hyperglycaemia, dyslipidaemia and oxidative stress prior to the development of type 2 diabetes mellitus. To date, a number of mechanisms have been proposed to link these syndromes together, but it remains unclear what the unifying condition that triggered these events in the progression of this metabolic disease. There have been a steady accumulation of data in numerous experimental studies showing the strong correlations between mitochondrial dysfunction, oxidative stress and insulin resistance. In addition, a growing number of studies suggest that the raised plasma free fatty acid level induced insulin resistance with the significant alteration of oxidative metabolism in various target tissues such as skeletal muscle, liver and adipose tissue. In this review, we herein propose the idea of long chain fatty acid-induced mitochondrial dysfunctions as one of the key events in the pathophysiological development of insulin resistance and type 2 diabetes. The accumulation of reactive oxygen species, lipotoxicity, inflammation-induced endoplasmic reticulum stress and alterations of mitochondrial gene subset expressions are the most detrimental that lead to the developments of aberrant intracellular insulin signalling activity in a number of peripheral tissues, thereby leading to insulin resistance and type 2 diabetes.

S-guanylation proteomics for redox-based mitochondrial signaling

AIMS

8-nitroguanosine 3',5'-cyclic monophosphate (8-Nitro-cGMP) is a nitrated derivative of cGMP that is formed via cross-talk of reactive oxygen species formed by NADPH oxidase 2 and mitochondria. This nitrated nucleotide can function as a unique electrophilic second messenger in regulation of redox signaling by inducing a post-translational modification of protein thiols via cGMP adduction (protein S-guanylation). With S-guanylation proteomics, we investigated endogenous mitochondrial protein S-guanylation.

RESULTS

We developed a new mass spectrometry (MS)-based proteomic method-S-guanylation proteomics-which comprised two approaches: (i) direct protein digestion followed by immunoaffinity capture of S-guanylated peptides that were subjected to liquid chromatography-tandem MS (LC-MS/MS); and (ii) two-dimensional (2D)-gel electrophoretic separation of S-guanylated proteins that were subjected to in-gel digestion, followed by LC-MS/MS. We thereby identified certain mitochondrial proteins that are S-guanylated endogenously during immunological stimulation, including mortalin and 60-kDa heat-shock protein (HSP60). Mortalin and HSP60 were recently reported to regulate mitochondrial permeability-transition pore (mPTP) opening, at least partly, by interacting with cyclophilin D, an mPTP component. Our data revealed that immunological stimulation and 8-nitro-cGMP treatment induced mPTP opening in a cyclophilin D-dependent manner.

INNOVATION AND CONCLUSION

Our S-guanylation proteomic method determined that mitochondrial HSPs may be novel targets for redox modification via protein S-guanylation that participates in mPTP regulation and mitochondrial redox signaling.

Oxidative stress in aging--matters of the heart and mind

Oxidative damage is considered to be the primary cause of several aging associated disease pathologies. Cumulative oxidative damage tends to be pervasive among cellular macromolecules, impacting proteins, lipids, RNA and DNA of cells. At a systemic level, events subsequent to oxidative damage induce an inflammatory response to sites of oxidative damage, often contributing to additional oxidative stress. At a cellular level, oxidative damage to mitochondria results in acidification of the cytoplasm and release of cytochrome c, causing apoptosis. This review summarizes findings in the literature on oxidative stress and consequent damage on cells and tissues of the cardiovascular system and the central nervous system, with a focus on aging-related diseases that have well-documented evidence of oxidative damage in initiation and/or progression of the disease. The current understanding of the cellular mechanisms with a focus on macromolecular damage, impacted cellular pathways and gross morphological changes associated with oxidative damage is also reviewed. Additionally, the impact of calorific restriction with its profound impact on cardiovascular and neuronal aging is addressed.

Evaluation of in vitro antioxidant capacity and reducing potential of polyherbal drug- Bhāraṅgyādi

Background:

Present work was designed to investigate antioxidant activity of polyherbal formulation in search for new, safe and inexpensive antioxidant. Clerodendrum serratum, Hedychium spicatum and Inula racemosa, were extensively used in ayurvedic medicine and were investigated together in the form of polyherbal compound (Bhāraṅgyādi) for their antioxidant potential.

Materials and Methods:

Hydroalcoholic extract was prepared from the above samples and was tested for total reducing power and in vitro antioxidant activity by ABTS⁺ assay, Superoxide anion scavenging activity assay and lipid per-oxidation assay.

Result:

Reducing power shows dose depended increase in concentration maximum absorption of 0.677 ± 0.017 at 1000 μg/ml compared with standard Quercetin 0.856±0.020. ABTS⁺ assay shows maximum inhibition of 64.2 ± 0.86 with EC₅₀ 675.31 ± 4.24. Superoxide free radical shows maximum scavenging activity of 62.45 ± 1.86 with EC₅₀ 774.70 ± 5.45. Anti-lipidperoxidation free radicals scavenge maximum absorption of 67.25± 1.89 with EC₅₀ is 700.08 ± 6.81. Ascorbic acid was used as standard with IC₅₀ value is 4.6 μg/ml. The result suggests polyherbal formulation to be a good potential for antioxidant activity. Oxidative stress results from imbalance between free radical-generation and radical scavenging systems. This will lead to tissue damage and oxidative stress.

Conclusion:

In conclusion, we strongly suggest that Polyherbal compounds are source of potential antioxidant for radical scavenging. The highly positive correlation of antiradical scavenging activity and total polyphenolic content in Polyherbal compounds indicates that polyphenols are important components which could be used for the free radical scavenging activity. Further study is needed for isolation and characterization of the active moiety responsible for biological activity and to treat in various stress condition.

Redox control of cardiac excitability

Reactive oxygen species (ROS) have been associated with various human diseases, and considerable attention has been paid to investigate their physiological effects. Various ROS are synthesized in the mitochondria and accumulate in the cytoplasm if the cellular antioxidant defense mechanism fails. The critical balance of this ROS synthesis and antioxidant defense systems is termed the redox system of the cell. Various cardiovascular diseases have also been affected by redox to different degrees. ROS have been indicated as both detrimental and protective, via different cellular pathways, for cardiac myocyte functions, electrophysiology, and pharmacology. Mostly, the ROS functions depend on the type and amount of ROS synthesized. While the literature clearly indicates ROS effects on cardiac contractility, their effects on cardiac excitability are relatively under appreciated. Cardiac excitability depends on the functions of various cardiac sarcolemal or mitochondrial ion channels carrying various depolarizing or repolarizing currents that also maintain cellular ionic homeostasis. ROS alter the functions of these ion channels to various degrees to determine excitability by affecting the cellular resting potential and the morphology of the cardiac action potential. Thus, redox balance regulates cardiac excitability, and under pathological regulation, may alter action potential propagation to cause arrhythmia. Understanding how redox affects cellular excitability may lead to potential prophylaxis or treatment for various arrhythmias. This review will focus on the studies of redox and cardiac excitation.

Intermittent hypoxia from obstructive sleep apnea may cause neuronal impairment and dysfunction in central nervous system: the potential roles played by microglia

Obstructive sleep apnea (OSA) is a common condition characterized by repetitive episodes of complete (apnea) or partial (hypopnea) obstruction of the upper airway during sleep, resulting in oxygen desaturation and arousal from sleep. Intermittent hypoxia (IH) resulting from OSA may cause structural neuron damage and dysfunction in the central nervous system (CNS). Clinically, it manifests as neurocognitive and behavioral deficits with oxidative stress and inflammatory impairment as its pathophysiological basis, which are mediated by microglia at the cellular level. Microglia are dominant proinflammatory cells in the CNS. They induce CNS oxidative stress and inflammation, mainly through mitochondria, reduced nicotinamide adenine dinucleotide phosphate oxidase, and the release of excitatory toxic neurotransmitters. The balance between neurotoxic versus protective and anti- versus proinflammatory microglial factors might determine the final roles of microglia after IH exposure from OSA. Microglia inflammatory impairments will continue and cascade persistently upon activation, ultimately resulting in clinically significant neuron damage and dysfunction in the CNS. In this review article, we summarize the mechanisms of structural neuron damage in the CNS and its concomitant dysfunction due to IH from OSA, and the potential roles played by microglia in this process.

NADPH oxidases as a source of oxidative stress and molecular target in ischemia/reperfusion injury

Ischemia/reperfusion injury (IRI) is crucial in the pathology of major cardiovascular diseases, such as stroke and myocardial infarction. Paradoxically, both the lack of oxygen during ischemia and the replenishment of oxygen during reperfusion can cause tissue injury. Clinical outcome is also determined by a third, post-reperfusion phase characterized by tissue remodeling and adaptation. Increased levels of reactive oxygen species (ROS) have been suggested to be key players in all three phases. As a second paradox, ROS seem to play a double-edged role in IRI, with both detrimental and beneficial effects. These Janus-faced effects of ROS may be linked to the different sources of ROS or to the different types of ROS that exist and may also depend on the phase of IRI. With respect to therapeutic implications, an untargeted application of antioxidants may not differentiate between detrimental and beneficial ROS, which might explain why this approach is clinically ineffective in lowering cardiovascular mortality. Under some conditions, antioxidants even appear to be harmful. In this review, we discuss recent breakthroughs regarding a more targeted and promising approach to therapeutically modulate ROS in IRI. We will focus on NADPH oxidases and their catalytic subunits, NOX, as they represent the only known enzyme family with the sole function to produce ROS. Similar to ROS, NADPH oxidases may play a dual role as different NOX isoforms may mediate detrimental or protective processes. Unraveling the precise sequence of events, i.e., determining which role the individual NOX isoforms play in the various phases of IRI, may provide the crucial molecular and mechanistic understanding to finally effectively target oxidative stress.

Carboxy terminus of heat shock protein (HSP) 70-interacting protein (CHIP) inhibits HSP70 in the heart

Heat shock protein (HSP) 70 plays a critical role in protecting the heart from various stressor-induced cell injuries; the mechanism remains to be further understood. The present study aims to elucidate the effect of a probiotics-derived protein, LGG-derived protein p75 (LGP), in alleviating the ischemia/reperfusion (I/R)-induced heart injury. We treated rats with the I/R with or without preadministration with LGP. The levels of HSP70 and carboxy terminus of HSP70-interacting protein (CHIP) in the heart tissue were assessed by enzyme-linked immunosorbent assay (ELISA) and Western blotting. The effect of CHIP on suppression of HSP70 and the effect of LGP on suppression of CHIP were investigated with an I/R rat model and a cell culture model. The results showed that I/R-induced infarction in the heart could be alleviated by pretreatment with LGP. HSP70 was detected in naïve rat heart tissue extracts. I/R treatment significantly suppressed the level of HSP70 and increased the levels of CHIP in the heart. A complex of CHIP/HSP70 was detected in heart tissue extracts. The addition of recombinant CHIP to culture inhibited HSP70 in heart cells. LGP was bound CHIP in heart cells and prevented the CHIP from binding HSP70. In summary, I/R can suppress HSP70 and increase CHIP in heart cells. CHIP can suppress HSP70 that can be prevented by pretreatment with LGP. The results imply that CHIP may be a potential target in the prevention of I/R-induced heart cell injury.

Stop the flow: a paradigm for cell signaling mediated by reactive oxygen species in the pulmonary endothelium

The lung endothelium is exposed to mechanical stimuli through shear stress arising from blood flow and responds to altered shear by activation of NADPH (NOX2) to generate reactive oxygen species (ROS). This review describes the pathway for NOX2 activation and the downstream ROS-mediated signaling events on the basis of studies of isolated lungs and flow-adapted endothelial cells in vitro that are subjected to acute flow cessation (ischemia). Altered mechanical stress is detected by a cell-associated complex involving caveolae and other membrane proteins that results in endothelial cell membrane depolarization and then the activation of specific kinases that lead to the assembly of NOX2 components. ROS generated by this enzyme amplify the mechanosignal within the endothelial cell to regulate activation and/or synthesis of proteins that participate in cell growth, proliferation, differentiation, apoptosis, and vascular remodeling. These responses indicate an important role for NOX2-derived ROS associated with mechanotransduction in promoting vascular homeostasis.

Reactive oxygen species and the brain in sleep apnea

Rodents exposed to intermittent hypoxia (IH), a model of obstructive sleep apnea (OSA), manifest impaired learning and memory and somnolence. Increased levels of reactive oxygen species (ROS), oxidative tissue damage, and apoptotic neuronal cell death are associated with the presence of IH-induced CNS dysfunction. Furthermore, treatment with antioxidants or overexpression of antioxidant enzymes is neuroprotective during IH. These findings mimic clinical cases of OSA and suggest that ROS may play a key causal role in OSA-induced neuropathology. Controlled production of ROS occurs in multiple subcellular compartments of normal cells and de-regulation of such processes may result in excessive ROS production. The mitochondrial electron transport chain, especially complexes I and III, and the NADPH oxidase in the cellular membrane are the two main sources of ROS in brain cells, although other systems, including xanthine oxidase, phospholipase A2, lipoxygenase, cyclooxygenase, and cytochrome P450, may all play a role. The initial evidence for NADPH oxidase and mitochondrial involvement in IH-induced ROS production and neuronal injury unquestionably warrants future research efforts.