Mitochondria-Targeted Peptide Reverses Mitochondrial Dysfunction and Cognitive Deficits in Sepsis-Associated Encephalopathy

SS-31 inhibits the inflammatory response by increasing ATG5 and promoting autophagy in lipopolysaccharide-stimulated HepG2 cells

SS-31 is a mitochondria-targeting short peptide. Recent studies have indicated its hepatoprotective effects. In our study, we investigated the impact of SS-31 on LPS-induced autophagy in HepG2 cells. The results obtained from a dual-fluorescence autophagy detection system revealed that SS-31 promotes the formation of autolysosomes and autophagosomes, thereby facilitating autophagic flux to a certain degree. Additionally, both ELISA and qPCR analyses provided further evidence that SS-31 safeguards HepG2 cells against inflammatory responses triggered by LPS through ATG5-dependent autophagy. In summary, our study demonstrates that SS-31 inhibits LPS-stimulated inflammation in HepG2 cells by upregulating ATG5-dependent autophagy.

GSDMD/Drp1 signaling pathway mediates hippocampal synaptic damage and neural oscillation abnormalities in a mouse model of sepsis-associated encephalopathy

BACKGROUND

Gasdermin D (GSDMD)-mediated pyroptotic cell death is implicated in the pathogenesis of cognitive deficits in sepsis-associated encephalopathy (SAE), yet the underlying mechanisms remain largely unclear. Dynamin-related protein 1 (Drp1) facilitates mitochondrial fission and ensures quality control to maintain cellular homeostasis during infection. This study aimed to investigate the potential role of the GSDMD/Drp1 signaling pathway in cognitive impairments in a mouse model of SAE.

METHODS

C57BL/6 male mice were subjected to cecal ligation and puncture (CLP) to establish an animal model of SAE. In the interventional study, mice were treated with the GSDMD inhibitor necrosulfonamide (NSA) or the Drp1 inhibitor mitochondrial division inhibitor-1 (Mdivi-1). Surviving mice underwent behavioral tests, and hippocampal tissues were harvested for histological analysis and biochemical assays at corresponding time points. Haematoxylin-eosin staining and TUNEL assays were used to evaluate neuronal damage. Golgi staining was used to detect synaptic dendritic spine density. Additionally, transmission electron microscopy was performed to assess mitochondrial and synaptic morphology in the hippocampus. Local field potential recordings were conducted to detect network oscillations in the hippocampus.

RESULTS

CLP induced the activation of GSDMD, an upregulation of Drp1, leading to associated mitochondrial impairment, neuroinflammation, as well as neuronal and synaptic damage. Consequently, these effects resulted in a reduction in neural oscillations in the hippocampus and significant learning and memory deficits in the mice. Notably, treatment with NSA or Mdivi-1 effectively prevented these GSDMD-mediated abnormalities.

CONCLUSIONS

Our data indicate that the GSDMD/Drp1 signaling pathway is involved in cognitive deficits in a mouse model of SAE. Inhibiting GSDMD or Drp1 emerges as a potential therapeutic strategy to alleviate the observed synaptic damages and network oscillations abnormalities in the hippocampus of SAE mice.

Role of CD36 in central nervous system diseases

CD36 is a highly glycosylated integral membrane protein that belongs to the scavenger receptor class B family and regulates the pathological progress of metabolic diseases. CD36 was recently found to be widely expressed in various cell types in the nervous system, including endothelial cells, pericytes, astrocytes, and microglia. CD36 mediates a number of regulatory processes, such as endothelial dysfunction, oxidative stress, mitochondrial dysfunction, and inflammatory responses, which are involved in many central nervous system diseases, such as stroke, Alzheimer's disease, Parkinson's disease, and spinal cord injury. CD36 antagonists can suppress CD36 expression or prevent CD36 binding to its ligand, thereby achieving inhibition of CD36-mediated pathways or functions. Here, we reviewed the mechanisms of action of CD36 antagonists, such as Salvianolic acid B, tanshinone IIA, curcumin, sulfosuccinimidyl oleate, antioxidants, and small-molecule compounds. Moreover, we predicted the structures of binding sites between CD36 and antagonists. These sites can provide targets for more efficient and safer CD36 antagonists for the treatment of central nervous system diseases.

Application research of novel peptide mitochondrial-targeted antioxidant SS-31 in mitigating mitochondrial dysfunction

Due to the pivotal role of mitochondria in the generation of adenosine triphosphate (ATP) and the regulation of cellular homeostasis, mitochondrial dysfunction may exert a profound impact on various physiological systems, potentially precipitating a spectrum of distinct diseases. Consequently, research pertaining to mitochondrial therapeutics has assumed increasing significance, warranting heightened scrutiny. In recent years, the field of mitochondrial therapy has witnessed noteworthy advancements, with active exploration into diverse pharmacological agents aimed at ameliorating mitochondrial function. Elamipretide (SS-31), a novel synthetic mitochondrial-targeted antioxidant, has emerged as a promising candidate with extensive therapeutic potential. Its notable attributes encompass the mitigation of oxidative stress, the suppression of inflammatory processes, the maintenance of mitochondrial dynamics, and the prevention of cellular apoptosis. As such, SS-31 may emerge as a viable choice for the treatment of mitochondrial dysfunction-related ailments in the foreseeable future. This article extensively expounds upon the superiority of SS-31 over natural antioxidants and traditional mitochondrial-targeted antioxidants, delves into its mechanisms of modulating mitochondrial function, and comprehensively summarizes its applications in alleviating mitochondrial dysfunction-associated disorders. Furthermore, we offer a comprehensive outlook on the expansive prospects of SS-31's future development and application.

Extracellular Vesicles Derived from Human Adipose-Derived Mesenchymal Stem Cells Alleviate Sepsis-Induced Acute Lung Injury through a MicroRNA-150-5p-Dependent Mechanism

Extracellular vesicles (EVs) derived from human adipose mesenchymal stem cells (hADSCs) may exert a therapeutic benefit in alleviating sepsis-induced organ dysfunction by delivering cargos that include RNAs and proteins to target cells. The current study aims to explore the protective effect of miR-150-5p delivered by hADSC-EVs on sepsis-induced acute lung injury (ALI). We noted low expression of miR-150-5p in plasma and bronchoalveolar lavage fluid samples from patients with sepsis-induced ALI. The hADSC-EVs were isolated and subsequently cocultured with macrophages. It was established that hADSC-EVs transferred miR-150-5p to macrophages, where miR-150-5p targeted HMGA2 to inhibit its expression and, consequently, inactivated the MAPK pathway. This effect contributed to the promotion of M2 polarization of macrophages and the inhibition of proinflammatory cytokines. Further, mice were made septic by cecal ligation and puncture in vivo and treated with hADSC-EVs to elucidate the effect of hADSC-EVs on sepsis-induced ALI. The in vivo experimental results confirmed a suppressive role of hADSC-EVs in sepsis-induced ALI. Our findings suggest that hADSC-EV-mediated transfer of miR-150-5p may be a novel mechanism underlying the paracrine effects of hADSC-EVs on the M2 polarization of macrophages in sepsis-induced ALI.

Potential of piperine for neuroprotection in sepsis-associated encephalopathy

AIMS

Sepsis-associated encephalopathy (SAE) is a common complication that increases mortality and leads to long-term cognitive impairment in sepsis survivors. However, no specific or effective therapy has been identified for this complication. Piperine is an alkaloid known for its anti-inflammatory, antioxidant, and neuroprotective properties, which are important characteristics for treatment of SAE. The objective of this study was to evaluate the neuroprotective effect of piperine on SAE in C57BL/6 mice that underwent cecum ligation and perforation surgery (CLP).

MAIN METHODS

C57BL/6 male mice were randomly assigned to groups that underwent SHAM surgery or CLP. Mice in the CLP group were treated with piperine at doses of 20 or 40 mg/kg for short- (5 days) or long-term (10 days) periods after CLP.

KEY FINDINGS

Our results revealed that untreated septic animals exhibited increased concentrations of IL-6, TNF, VEGF, MMP-9, TBARS, and NLRP3, and decreased levels of BDNF, sulfhydryl groups, and catalase in the short term. Additionally, the levels of carbonylated proteins and degenerated neuronal cells were increased at both time points. Furthermore, short-term and visuospatial memories were impaired. Piperine treatment reduced MMP-9 activity in the short term and decreased the levels of carbonylated proteins and degenerated neuronal cells in the long term. It also lowered IL-6 and TBARS levels at both time points evaluated. Moreover, piperine increased short-term catalase and long-term BDNF factor levels and improved memory at both time points.

SIGNIFICANCE

In conclusion, our data demonstrate that piperine exerts a neuroprotective effect on SAE in animals that have undergone CLP.

Nicotinamide mononucleotide as a therapeutic agent to alleviate multi-organ failure in sepsis

BACKGROUND

Sepsis-caused multi-organ failure remains the major cause of morbidity and mortality in intensive care units with limited therapeutics. Nicotinamide mononucleotide (NMN), a precursor of nicotinamide adenine dinucleotide (NAD+), has been recently reported to be protective in sepsis; however, its therapeutic effects remain to be determined. This study sought to investigate the therapeutic effects of NMN in septic organ failure and its underlying mechanisms.

METHODS

Sepsis was induced by feces-injection-in-peritoneum in mice. NMN was given after an hour of sepsis onset. Cultured neutrophils, macrophages and endothelial cells were incubated with various agents.

RESULTS

We demonstrate that administration of NMN elevated NAD+ levels and reduced serum lactate levels, oxidative stress, inflammation, and caspase-3 activity in multiple organs of septic mice, which correlated with the attenuation of heart dysfunction, pulmonary microvascular permeability, liver injury, and kidney dysfunction, leading to lower mortality. The therapeutic effects of NMN were associated with lower bacterial burden in blood, and less ROS production in septic mice. NMN improved bacterial phagocytosis and bactericidal activity of macrophages and neutrophils while reducing the lipopolysaccharides-induced inflammatory response of macrophages. In cultured endothelial cells, NMN mitigated mitochondrial dysfunction, inflammation, apoptosis, and barrier dysfunction induced by septic conditions, all of which were offset by SIRT3 inhibition.

CONCLUSION

NAD+ repletion with NMN prevents mitochondrial dysfunction and restrains bacterial dissemination while limiting inflammatory damage through SIRT3 signaling in sepsis. Thus, NMN may represent a therapeutic option for sepsis.

Involvement of cannabinoid receptors and neuroinflammation in early sepsis: Implications for posttraumatic stress disorder

Sepsis is associated with several comorbidities in survivors, such as posttraumatic stress disorder (PTSD). This study investigated whether rats that survive sepsis develop the generalization of fear memory as a model of PTSD. Responses to interventions that target the endothelin-1 (ET-1)/cannabinoid system and glial activation in the initial stages of sepsis were evaluated. As a control, we evaluated hyperalgesia before fear conditioning. Sepsis was induced by cecal ligation and puncture (CLP) in Wistar rats. CLP-induced sepsis with one or three punctures resulted in fear generalization in the survivors 13 and 20 days after the CLP procedure, a process that was not associated with hyperalgesia. Septic animals were intracerebroventricularly treated with vehicle, the endothelin receptor A (ETA) antagonist BQ123, the cannabinoid CB1 and CB2 receptor antagonists AM251 and AM630, respectively, and the glial blocker minocycline 4 h after CLP. The blockade of either CB1 or ETA receptors increased the survival rate, but only the former reversed fear memory generalization. The endothelinergic system blockade is important for improving survival but not for fear memory. Treatment with the CB2 receptor antagonist or minocycline also reversed the generalization of fear memory but did not increase the survival rate that was associated with CLP. Minocycline treatment also reduced tumor necrosis factor-α levels in the hippocampus suggesting that neuroinflammation is important for the generalization of fear memory induced by CLP. The influence of CLP on the generalization of fear memory was not related to Arc protein expression, a regulator of synaptic plasticity, in the dorsal hippocampus.

Elamipretide reduces pyroptosis and improves functional recovery after spinal cord injury

AIMS

Elamipretide (EPT), a novel mitochondria-targeted peptide, has been shown to be protective in a range of diseases. However, the effect of EPT in spinal cord injury (SCI) has yet to be elucidated. We aimed to investigate whether EPT would inhibit pyroptosis and protect against SCI.

METHODS

After establishing the SCI model, we determined the biochemical and morphological changes associated with pyroptosis, including neuronal cell death, proinflammatory cytokine expression, and signal pathway levels. Furthermore, mitochondrial function was assessed with flow cytometry, quantitative real-time polymerase chain reaction, and western blot.

RESULTS

Here, we demonstrate that EPT improved locomotor functional recovery following SCI as well as reduced neuronal loss. Moreover, EPT inhibited nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) inflammasome activation and pyroptosis occurrence and decreased pro-inflammatory cytokines levels following SCI. Furthermore, EPT alleviated mitochondrial dysfunction and reduced mitochondrial reactive oxygen species level.

CONCLUSION

EPT treatment may protect against SCI via inhibition of pyroptosis.

HSPB8 up-regulation alleviates cognitive dysfunction in a mouse model of sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE) is associated with a higher risk of cognitive deficits; however, its potential mechanisms are still unknow. Recently, researches show that HSPB8, a family of small heat shock proteins, affects cognitive function and ameliorates sepsis-induced dysfunction. However, the role of HSPB8 in SAE-associated cognitive impairment has not been elucidated. In this study, we found that HSPB8 expression was up-regulated in the brain of mice with lipopolysaccharide-induced sepsis. HSPB8 overexpression alleviated cognitive decline in SAE mice. In addition, exogenous HSPB8 exerts neuroprotective effects and salvages synaptic function via regulating NRF1/TFAM-induced mitochondrial biogenesis and DRP1-mediate mitochondrial fission in a lipopolysaccharide-induced mouse model. Furthermore, HSPB8 overexpression inhibits IBA1 and NLRP3 activation in the SAE model. Overexpression of HSPB8 may be an efficient treatment for relieving SAE-related cognitive decline.

Acute and long-term cognitive impairment following sepsis: mechanism and prevention

INTRODUCTION

Sepsis is a severe host response to infection, which induces both acute and long-term cognitive impairment. Despite its high incidence following sepsis, the underlying mechanisms remain elusive and effective treatments are not available clinically.

AREA COVERED

This review focuses on elucidating the pathological mechanisms underlying cognitive impairment following sepsis. Specifically, the authors discuss the role of systemic inflammation response, blood-brain barrier disruption, neuroinflammation, mitochondrial dysfunction, neuronal dysfunction, and Aβ accumulation and tau phosphorylation in cognitive impairment after sepsis. Additionally, they review current strategies to ameliorate cognitive impairment.

EXPERT OPINION

Potential interventions to reduce cognitive impairment after sepsis include earlier diagnosis and effective infection control, hemodynamic homeostasis, and adequate brain perfusion. Furthermore, interventions to reduce inflammatory response, reactive oxygen species, blood-brain barrier disruption, mitochondrial dysfunction, neuronal injury or death could be beneficial. Implementing strategies to minimize delirium, sleep disturbance, stress factors, and immobility are also recommended. Furthermore, avoiding neurotoxins and implementing early rehabilitation may also be important for preventing cognitive impairment after sepsis.

Neurochemical effects of sepsis on the brain

Sepsis is a life-threatening organ dysfunction triggered by a dysregulated host immune response to eliminate an infection. After the host immune response is activated, a complex, dynamic, and time-dependent process is triggered. This process promotes the production of inflammatory mediators, including acute-phase proteins, complement system proteins, cytokines, chemokines, and antimicrobial peptides, which are required to initiate an inflammatory environment for eliminating the invading pathogen. The physiological response of this sepsis-induced systemic inflammation can affect blood-brain barrier (BBB) function; subsequently, endothelial cells produce inflammatory mediators, including cytokines, chemokines, and matrix metalloproteinases (MMPs) that degrade tight junction (TJ) proteins and decrease BBB function. The resulting BBB permeability allows peripheral immune cells from the bloodstream to enter the brain, which then release a range of inflammatory mediators and activate glial cells. The activated microglia and astrocytes release reactive oxygen species (ROS), cytokines, chemokines, and neurochemicals, initiate mitochondrial dysfunction and neuronal damage, and exacerbate the inflammatory milieu in the brain. These changes trigger sepsis-associated encephalopathy (SAE), which has the potential to increase cognitive deterioration and susceptibility to cognitive decline later in life.

Dexpramipexole ameliorates cognitive deficits in sepsis-associated encephalopathy through suppressing mitochondria-mediated pyroptosis and apoptosis

OBJECTIVES

This study was aimed at evaluating the effects of dexpramipexole (DPX) - a mitochondrial protectant that sustains mitochondrial function and energy production - on cognitive function in a mouse model of sepsis-associated encephalopathy (SAE) induced by peripheral administration of lipopolysaccharide (LPS) and examining the potential mechanisms.

METHODS

C57BL/6 male mice were randomized into one of four treatment protocols: Con+Sal, Con+DPX, LPS+Sal or LPS+DPX. The mice were intraperitoneally (i.p.) injected with LPS or equivalent volumes of normal saline once daily for 3 consecutive days. To evaluate the protective effects of DPX, we administered DPX or normal saline i.p. to the mice once daily for 6 consecutive days. Six mice in each group were decapitated on day 7, and each brain was rapidly removed and separated into two halves for biochemical and histochemical analysis. The remaining surviving mice in each group were subjected to behavioral tests from days 7 to 10.

RESULTS

Peripheral administration of LPS to mice led to learning and memory deficits in behavioral tests, which were associated with mitochondrial impairment and ATP depletion in the hippocampus. Repeated DPX treatment protected the mitochondria against LPS-induced morphological and functional impairment; inhibited the activation of the Nod-like receptor pyrin domain-containing 3 (NLRP3) inflammasome-caspase-1-dependent pyroptosis pathway and cytochrome c (Cyt-c)-caspase-3-dependent apoptosis pathway; and attenuated LPS-induced neuroinflammation and cell death in the hippocampus in SAE mice.

CONCLUSIONS

Mitochondria-mediated pyroptosis and apoptosis are involved in the pathogenesis of cognitive deficits in a mouse model of SAE and DPX protects mitochondria and suppresses the mitochondria-medicated pyroptosis and apoptosis pathways, and ameliorates LPS-induced neuroinflammation and cognitive deficits. This study provides theoretical evidence supporting DPX for the treatment of SAE.

Reduced inhibitory and excitatory input onto parvalbumin interneurons mediated by perineuronal net might contribute to cognitive impairments in a mouse model of sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE) is commonly defined as diffuse brain dysfunction and can manifest as delirium to coma. Accumulating evidence has suggested that perineuronal net (PNN) plays an important role in the modulation of the synaptic plasticity of central nervous system. We here investigated the role of PNN in SAE induced by lipopolysaccharide (LPS) injection. Behavioral tests were performed by open field, Y-maze, and fear conditioning tests at the indicated time points. The densities of vesicular γ-aminobutyric acid transporter, vesicular glutamate transporter 1, PNN, and parvalbumin (PV) in the hippocampus were evaluated by immunofluorescence. Matrix metalloproteinases-9 (MMP-9) expression and its activity were detected by Western blot and gel zymography, respectively. Local field potential was recorded by in vivo electrophysiology. LPS-treated mice displayed significant cognitive impairments, coincided with activated MMP-9, decreased PNN and PV densities, reduced inhibitory and excitatory input onto PV interneurons enwrapped by PNN, and decreased gamma oscillations in hippocampal CA1. Notably, MMP-9 inhibitor SB-3CT treatment rescued most of these abnormalities. Taken together, our study demonstrates that active MMP-9 mediated PNN remodeling, leading to reduced inhibitory and excitatory input onto PV interneurons and abnormal gamma oscillations in hippocampal CA1, which consequently contributed to cognitive impairments after LPS injection.

Non-hepatic Hyperammonemia: A Potential Therapeutic Target for Sepsis-associated Encephalopathy

Sepsis-Associated Encephalopathy (SAE) is a common complication in the acute phase of sepsis, and patients who develop SAE have a higher mortality rate, longer hospital stay, and worse quality of life than other sepsis patients. Although the incidence of SAE is as high as 70% in sepsis patients, no effective treatment is available for this condition. To develop an effective treatment for SAE, it is vital to explore its pathogenesis. It is known that hyperammonemia is a possible factor in the pathogenesis of hepatic encephalopathy as ammonia is a potent neurotoxin. Furthermore, our previous studies indicate that non-hepatic hyperammonemia seems to occur more often in sepsis patients; it was also found that >50% of sepsis patients with non-hepatic hyperammonemia exhibited encephalopathy and delirium. Substatistical analyses indicate that non-hepatic hyperammonemia is an independent risk factor for SAE. This study updates the definition, clinical manifestations, and diagnosis of SAE; it also investigates the possible treatment options available for non-hepatic hyperammonemia in patients with sepsis and the mechanisms by which non-hepatic hyperammonemia causes encephalopathy.

Irisin protects against sepsis-associated encephalopathy by suppressing ferroptosis via activation of the Nrf2/GPX4 signal axis

Sepsis-associated encephalopathy (SAE) is a common complication of severe sepsis. Irisin is a novel exercise-induced myokine involved in the regulation of adipose browning and thermogenesis. This study is designed to verify the existence of ferroptosis in the pathogenesis of SAE and demonstrate that irisin attenuated cognitive dysfunction in SAE mice via inhibition of hippocampus ferroptosis. A mouse SAE model was induced by cecal ligation and puncture (CLP) and in vitro model was established by LPS-stimulated hippocampus cells. Irisin were pre-treated in the models. We found that SAE triggered hippocampus ferroptosis, as evidenced by increasing ROS, iron content and MDA and reducing GSH level as well as altered ferroptosis-related protein (GPX4, ACSL4 and SLC7A11) expression, whereas irisin attenuated CLP-induced learning and memory dysfunction, neurologic severity score and hippocampus ferroptosis and microglial activation in SAE mice. However, the protective effect of irisin was eliminated by ferroptosis inducer Erastin. Consistently, irisin reduced ferroptosis and improved mitochondrial dysfunction in LPS-induced HT-22 cells, as evidenced by decreased lipid ROS and increased mitochondrial membrane potential. Furthermore, proteomics identified the differentially expressed proteins linked to ferroptosis in SAE. We also observed that irisin-mediated anti-ferroptosis was abolished by siRNA-Nrf2 or in Nrf2^-/- mice. Transwell assay revealed that irisin could prevent the recruitment and chemotaxis of microglial cells induced by ferroptotic hippocampal cells. In conclusion, irisin could ameliorate inflammatory microenvironment in SAE by suppressing hippocampus ferroptosis via the Nrf2/GPX4 signaling pathway.

Mitochondrial-Targeted Antioxidant Peptide SS31 Prevents RPE Cell Death under Oxidative Stress

This work aims at investigating the protective effects of the mitochondria-targeted peptide SS31, on mitochondria function, preventing human retinal pigment epithelial cell-19 (ARPE-19) cell apoptosis. The ARPE-19 cells were subjected to 24 h of intervention with H2O2 of various concentrations (0, 100, 150, 200, 250, 300, and 500 μmol/L). Various concentrations of SS31 (10 nM, 100 nM, and 1 μmol/L) pretreated the cells for 2 h. The MTT assay determined cell viability. ARPE-19 cell apoptosis was observed by 4',6-diamidino-2-phenylindole (DAPI) staining under fluorescence microscope and detected by Annexin-V/PI staining under flow cytometry. The measurement of reactive oxygen species (ROS) release level used MitoSOX Red (a mitochondrial superoxide indicator) and the probe 2'-7'dichlorofluorescin diacetate (DCFH-DA). And with the use of a JC-1 probe, the mitochondrial membrane potential (MMP; ΔΨm) was analyzed. Reverse transcription polymerase chain reaction (RT-PCR) and real-time PCR were responsible for measuring the levels of apoptosis related genes (Bcl-2, Bax, and Caspase-3). The cell viability increased significantly with SS31 pretreated (P < 0.05). In the SS31 + H2O2 group, the fluorescence of the cell nuclei with DAPI staining was weaker than H2O2 along group accordance with the decreased ratio of apoptotic cells (P < 0.05). The ROS generation decreased in SS31 pretreated group, with the increased ΔΨm. The RT-PCR result showed decreased Bax gene and Caspase-3 gene expression with SS31 pretreatment, while increased antiapoptotic gene Bcl-2 (P < 0.05). We provide evidence that SS31 promotes resilience of RPE cells to oxidative stress by stabilizing mitochondrial function.

Dendrobium Nobile Lindl. Alkaloid Suppresses NLRP3-Mediated Pyroptosis to Alleviate LPS-Induced Neurotoxicity

Alzheimer’s disease (AD) is a neurodegenerative disorder recognized as a global public health priority. Although available treatments temporarily relieve the symptoms, they could not prevent the progression of cognitive decline. Natural compounds have been rich sources for drug discovery. Dendrobium nobile Lindl. alkaloid (DNLA) is the main active compound in Dendrobium nobile Lindl, a traditional Chinese herbal medicine. Recent studies indicated that DNLA produced neuroprotection. However, the mechanisms underlying DNLA-generated neuroprotection remain unknown. To investigate neuroprotection and the underlying mechanisms of DNLA, mouse hippocampus injection of lipopolysaccharide (LPS)-induced neuronal damage was performed. DNLA protected hippocampus neurons and working memory disorder against LPS-induced neurotoxicity. In addition, DNLA suppressed cell undergoing membrane lysis and cell swelling and inhibited the essential mediator of pyroptosis GSDMD-N expressions. Furthermore, DNLA-mediated neuroprotection was dependent on the inhibition of NLRP3 inflammasome activation, as evidenced by the fact that DNLA reduced pro-inflammatory factor (IL-18 and IL-1β) production and inhibited the expression of related proteins. DNLA-exerted neuroprotection against LPS-induced neuronal damage, and cognitive impairment was not observed in NLRP3 knockout mice. Together, this study suggested that DNLA attenuated NLRP3-mediated pyroptosis to generate neuroprotection against LPS-induced neuronal damage and cognitive impairment.

Neuroprotective Effects of a Small Mitochondrially-Targeted Tetrapeptide Elamipretide in Neurodegeneration

Neural mitochondrial dysfunction, neural oxidative stress, chronic neuroinflammation, toxic protein accumulation, and neural apoptosis are common causes of neurodegeneration. Elamipretide, a small mitochondrially-targeted tetrapeptide, exhibits therapeutic effects and safety in several mitochondria-related diseases. In neurodegeneration, extensive studies have shown that elamipretide enhanced mitochondrial respiration, activated neural mitochondrial biogenesis via mitochondrial biogenesis regulators (PCG-1α and TFAM) and the translocate factors (TOM-20), enhanced mitochondrial fusion (MNF-1, MNF-2, and OPA1), inhibited mitochondrial fission (Fis-1 and Drp-1), as well as increased mitophagy (autophagy of mitochondria). In addition, elamipretide has been shown to attenuate neural oxidative stress (hydrogen peroxide, lipid peroxidation, and ROS), neuroinflammation (TNF, IL-6, COX-2, iNOS, NLRP3, cleaved caspase-1, IL-1β, and IL-18), and toxic protein accumulation (Aβ). Consequently, elamipretide could prevent neural apoptosis (cytochrome c, Bax, caspase 9, and caspase 3) and enhance neural pro-survival (Bcl2, BDNF, and TrkB) in neurodegeneration. These findings suggest that elamipretide may prevent the progressive development of neurodegenerative diseases via enhancing mitochondrial respiration, mitochondrial biogenesis, mitochondrial fusion, and neural pro-survival pathway, as well as inhibiting mitochondrial fission, oxidative stress, neuroinflammation, toxic protein accumulation, and neural apoptosis. Elamipretide or mitochondrially-targeted peptide might be a targeted agent to attenuate neurodegenerative progression.

Basic research and clinical progress of sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE), a major cerebral complication of sepsis, occurs in 70% of patients admitted to the intensive care unit (ICU). This condition can cause serious impairment of consciousness and is associated with a high mortality rate. Thus far, several experimental screenings and radiological techniques (e.g., electroencephalography) have been used for the non-invasive assessment of the structure and function of the brain in patients with SAE. Nevertheless, the pathogenesis of SAE is complicated and remains unclear. In the present article, we reviewed the currently available literature on the epidemiology, clinical manifestations, pathology, diagnosis, and management of SAE. However, currently, there is no ideal pharmacological treatment for SAE. Treatment targeting mitochondrial dysfunction may be useful in the management of SAE.

Protective effects and mechanisms of high-dose vitamin C on sepsis-associated cognitive impairment in rats

Sepsis survivors present long-term cognitive deficits. The present study was to investigate the effect of early administration of high-dose vitamin C on cognitive function in septic rats and explore its possible cerebral protective mechanism. Rat sepsis models were established by cecal ligation and puncture (CLP). Ten days after surgery, the Morris water maze test was performed to evaluate the behavior and cognitive function. Histopathologic changes in the hippocampus were evaluated by nissl staining. The inflammatory cytokines, activities of antioxidant enzymes (superoxide dismutase or SOD) and oxidative products (malondialdehyde or MDA) in the serum and hippocampus were tested 24 h after surgery. The activity of matrix metalloproteinase-9 (MMP-9) and expressions of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1(HO-1) in the hippocampus were measured 24 h after surgery. Compared with the sham group in the Morris water maze test, the escape latency of sepsis rats was significantly (P = 0.001) prolonged in the navigation test, whereas the frequency to cross the platform and the time spent in the target quadrant were significantly (P = 0.003) reduced. High-dose vitamin C significantly decreased the escape latency (P = 0.01), but increased the time spent in the target quadrant (P = 0.04) and the frequency to cross the platform (P = 0.19). In the CLP+ saline group, the pyramidal neurons were reduced and distributed sparsely and disorderly, the levels of inflammatory cytokines of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-10 in the serum and hippocampus were significantly increased (P = 0.000), the blood brain barrier (BBB) permeability in the hippocampus was significantly (P = 0.000) increased, the activities of SOD in the serum and hippocampus were significantly (P = 0.000 and P = 0.03, respectively) diminished while the levels of MDA in the serum and hippocampus were significantly (P = 0.007) increased. High-dose vitamin C mitigated hippocampus histopathologic changes, reduced systemic inflammation and neuroinflammation, attenuated BBB disruption, inhibited oxidative stress in brain tissue, and up-regulated the expression of nuclear and total Nrf2 and HO-1. High-dose vitamin C significantly (P < 0.05) decreased the levels of tumor necrosis factor- (TNF)-α, interleukin-6 (IL-6), MDA in the serum and hippocampus, and the activity of MMP-9 in the hippocampus, but significantly (P < 0.05) increased the levels of SOD, the anti-inflammatory cytokine (IL-10) in the serum and hippocampus, and nuclear and total Nrf2, and HO-1 in the hippocampus. In conclusion, high-dose vitamin C can improve cognition impairment in septic rats, and the possible protective mechanism may be related to inhibition of inflammatory factors, alleviation of oxidative stress, and activation of the Nrf2/HO-1 pathway.

Mini-Review: Mitochondrial dysfunction and chemotherapy-induced neuropathic pain

Chemotherapy-induced peripheral neuropathy (CIPN) is a somatosensory axonopathy in cancer patients receiving any of a variety of widely-use antitumor agents. CIPN can lead to long-lasting neuropathic pain that limits the dose or length of otherwise life-saving cancer therapy. Accumulating evidence over the last two decades indicates that many chemotherapeutic agents cause mitochondrial injury in the peripheral sensory nerves by disrupting mitochondrial structure and bioenergetics, increasing nitro-oxidative stress and altering mitochondrial transport, fission, fusion and mitophagy. The accumulation of abnormal and dysfunctional mitochondria in sensory neurons are linked to axonal growth defects resulting in the loss of intraepidermal nerve fibers in the hands and feet, increased spontaneous discharge and the sensitization of peripheral sensory neurons that provoke and promote changes in the central nervous system that establish a chronic neuropathic pain state. This has led to the propose mitotoxicity theory of CIPN. Strategies that improve mitochondrial function have shown success in preventing and reversing CIPN in pre-clinical animal models and have begun to show some progress toward translation to the clinic. In this review, we will review the evidence for, the causes and effects of and current strategies to target mitochondrial dysfunction in CIPN.

Melatonin ameliorates ochratoxin A induced liver inflammation, oxidative stress and mitophagy in mice involving in intestinal microbiota and restoring the intestinal barrier function

The mycotoxin ochratoxin A (OTA) is a widespread contaminant in human and animal food products. Previous studies in rats revealed that melatonin (Mel) exhibits a preventive effect against OTA-induced oxidative stress in liver. However, it remains unknown whether gut microbiota respond to Mel and, if so, whether it can prevent OTA-induced inflammation and mitophagy in the liver. In the present study, mice received an oral gavage of Mel and OTA for 3 weeks before harvesting colonic digesta and liver tissue for analyses. In another study, the role of intestinal microbiota on the effects of Mel on OTA-induced liver inflammation and mitophagy was assessed through clearance of intestinal microbiota with antibiotics followed by gut microbiota transplantation (GMT). Oral Mel supplementation ameliorated mitophagy in the liver and reversed gut microbiota dysbiosis. Intriguingly, in antibiotic-treated mice, Mel and OTA failed to induce mitophagy in the liver. Using the GMT approach in which mice were colonised with intestinal microbiota from control-, OTA-, or Mel + OTA-treated mice led us to elucidated the involvement of intestinal microbiota in liver inflammation and mitophagy induced by OTA. The findings suggested that intestinal microbiota play some role in the Mel-induced amelioration of liver inflammation and mitophagy induced by OTA.

Antioxidant effect of Elamipretide on bull's sperm cells during freezing/thawing process

BACKGROUND

Spermatozoa are subjected to drastic changes in temperature, ice crystal formation, and diverse types of stresses (chemical, physical, osmotic, and oxidative) during the cryopreservation process, which severely compromise sperm quality and fertility. In this study, we aimed to investigate the protective role of Elamipretide in the cryopreservation of bull's spermatozoa.

MATERIALS AND METHODS

The study included 36 healthy Simmental bulls with an average age of 2 ± 0.5 years housed individually in pens. Two ejaculates were collected from each bull using an artificial vagina at 7 a.m. Subsequently, the semen was extended with animal protein-free commercial BIOXcell® extender (IMV Technologies) to a final concentration of 160 × 10⁶ spermatozoa/ml, and rated in terms of motile sperm percentage, progressive motility, viability, and morphological abnormality of spermatozoa. Semen samples that showed more than 60% motility and 60% viability, were selected for the experiment. The fresh semen was then divided into five equal fractions. The first fraction was left for the control group (without Elamipretide), to the next were added in succession 0.1; 1; 5; and 10 μM of Elamipretide TFA (Trifluoroacetic) (MedChemExpress). After that semen was subjected to freezing and thawing. Next semen was assessed for motility, viability, mitochondrial membrane potential and acrosome integrity, and antioxidant activity (SOD, CAT, MDA).

RESULTS

It has been shown that a concentration of 5 and 10 μM proved to be the most effective in terms of tested parameters of the quality of sperm cells subjected to cryopreservation.

CONCLUSION

In conclusion, addition of the Elamipretide to the cryopreservation extender significantly improved frozen-thawed sperm cells quality and their function. The results of this study indicate that Elamipretide can be used as a cryoprotective agent to protect cells against the devastating effects of oxidative stress and increasing sperm survival after cryopreservation.

The Neuroprotective Effect of Short Chain Fatty Acids Against Sepsis-Associated Encephalopathy in Mice

Short chain fatty acids (SCFAs) are known to be actively involved in multiple brain disorders, but their roles in sepsis-associated encephalopathy (SAE) remain unclear. Here, we investigated the neuroprotective effects of SCFAs on SAE in mice. Male C57BL/6 mice were intragastrically pretreated with SCFAs for seven successive days, and then subjected to SAE induced by cecal ligation and puncture. The behavioral impairment, neuronal degeneration, and levels of inflammatory cytokines were assessed. The expressions of tight junction (TJ) proteins, including occludin and zoula occludens-1 (ZO-1), cyclooxygenase-2 (COX-2), cluster of differentiation 11b (CD11b), and phosphorylation of JNK and NF-κB p65 in the brain, were measured by western blot and Immunofluorescence analysis. Our results showed that SCFAs significantly attenuated behavioral impairment and neuronal degeneration, and decreased the levels of IL-1β and IL-6 in the brain of SAE mice. Additionally, SCFAs upregulated the expressions of occludin and ZO-1 and downregulated the expressions of COX-2, CD11b, and phosphorylation of JNK and NF-κB p65 in the brain of SAE mice. These findings suggested that SCFAs could exert neuroprotective effects against SAE in mice.

Protective Effect of Mitochondria-Targeted Antioxidants against Inflammatory Response to Lipopolysaccharide Challenge: A Review

Lipopolysaccharide (LPS), the major component of the outer membrane of Gram-negative bacteria, is the most abundant proinflammatory agent. Considerable evidence indicates that LPS challenge inescapably causes oxidative stress and mitochondrial dysfunction, leading to cell and tissue damage. Increased mitochondrial reactive oxygen species (mtROS) generation triggered by LPS is known to play a key role in the progression of the inflammatory response. mtROS at excessive levels impair electron transport chain functioning, reduce the mitochondrial membrane potential, and initiate lipid peroxidation and oxidative damage of mitochondrial proteins and mtDNA. Over the past 20 years, a large number of mitochondria-targeted antioxidants (mito-AOX) of different structures that can accumulate inside mitochondria and scavenge free radicals have been synthesized. Their protective role based on the prevention of oxidative stress and the restoration of mitochondrial function has been demonstrated in a variety of common diseases and pathological states. This paper reviews the current data on the beneficial application of different mito-AOX in animal endotoxemia models, in either in vivo or in vitro experiments. The results presented in our review demonstrate the promising potential of approaches based on mito-AOX in the development of new treatment strategies against Gram-negative infections and LPS per se.

Mitochondrial Fission Protein 1: Emerging Roles in Organellar Form and Function in Health and Disease

Mitochondrial fission protein 1 (Fis1) was identified in yeast as being essential for mitochondrial division or fission and subsequently determined to mediate human mitochondrial and peroxisomal fission. Yet, its exact functions in humans, especially in regard to mitochondrial fission, remains an enigma as genetic deletion of Fis1 elongates mitochondria in some cell types, but not others. Fis1 has also been identified as an important component of apoptotic and mitophagic pathways suggesting the protein may have multiple, essential roles. This review presents current perspectives on the emerging functions of Fis1 and their implications in human health and diseases, with an emphasis on Fis1's role in both endocrine and neurological disorders.

Maf1 Ameliorates Sepsis-Associated Encephalopathy by Suppressing the NF-kB/NLRP3 Inflammasome Signaling Pathway

Background

The NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome has been identified as an important mediator of blood–brain-barrier disruption in sepsis-associated encephalopathy (SAE). However, no information is available concerning the critical upstream regulators of SAE.

Methods

Lipopolysaccharide (LPS) was used to establish an in vitro model of blood–brain barrier (BBB) disruption and an in vivo model of SAE. Disruption of BBB integrity was assessed by measuring the expression levels of tight-junction proteins. NLRP3 inflammasome activation, pro-inflammatory cytokines levels, and neuroapoptosis were measured using biochemical assays. Finally, the FITC-dextran Transwell assay and Evan’s blue dye assay were used to assess the effect of Maf1 on LPS-induced endothelial permeability in vitro and in vivo.

Results

We found that Maf1 significantly suppressed the brain inflammatory response and neuroapoptosis induced by LPS in vivo and in vitro. Notably, Maf1 downregulated activation of the NF-κB/p65-induced NLRP3 inflammasome and the expression of pro-inflammatory cytokines. In addition, we found that Maf1 and p65 directly bound to the NLRP3 gene promoter region and competitively regulated the function of NLRP3 in inflammations. Moreover, overexpression of NLRP3 reversed the effects of p65 on BBB integrity, apoptosis, and inflammation in response to LPS. Our study revealed novel role for Maf1 in regulating NF-κB-mediated inflammasome formation, which plays a prominent role in SAE.

Conclusions

Regulation of Maf1 might be a therapeutic strategy for SAE and other neurodegenerative diseases associated with inflammation.

What animal models can tell us about long-term cognitive dysfunction following sepsis: A systematic review

Survivors of sepsis often develop long-term cognitive impairments. This review aimed at exploring the results of the behavioral tools and tests which have been used to evaluate cognitive dysfunction in different animal models of sepsis. Two independent investigators searched for sepsis- and cognition-related keywords. 6323 publications were found, of which 355 were selected based on their title, and 226 of these were chosen based on manuscript review. LPS was used to induce sepsis in 171 studies, while CLP was used in 55 studies. Inhibitory avoidance was the most widely used method for assessing aversive memory, followed by fear conditioning and continuous multi-trial inhibitory avoidance. With regard to non-aversive memory, most studies used the water maze, open-field, object recognition, Y-maze, plus maze, and radial maze tests. Both CLP and LPS models of sepsis were effective in inducing short- and long-term behavioral impairment. Our findings help elucidate the mechanisms involved in the pathophysiology of sepsis-induced cognitive changes, as well as the available methods and tests used to study this in animal models.

NLRP3 Activation Contributes to Acute Brain Damage Leading to Memory Impairment in Sepsis-Surviving Rats

Sepsis survivors present acute and long-term cognitive impairment and the pathophysiology of neurological dysfunction in sepsis involves microglial activation. Recently, the involvement of cytosolic receptors capable of forming protein complexes called inflammasomes have been demonstrated to perpetuate neuroinflammation. Thus, we investigated the involvement of the NLRP3 inflammasome activation on early and late brain changes in experimental sepsis. Two-month-old male Wistar rats were submitted to the sepsis model by cecal ligation and perforation (CLP group) or laparotomy only (sham group). Immediately after surgery, the animals received saline or NLRP3 inflammasome formation inhibitor (MCC950, 140 ng/kg) intracerebroventricularly. Prefrontal cortex and hippocampus were isolated for cytokine analysis, microglial and astrocyte activation, oxidative stress measurements, nitric oxide formation, and mitochondrial respiratory chain activity at 24 h after CLP. A subset of animals was followed for 10 days for survival assessment, and then behavioral tests were performed. The administration of MCC950 restored the elevation of IL-1β, TNF-α, IL-6, and IL-10 cytokine levels in the hippocampus. NLRP3 receptor levels increased in the prefrontal cortex and hippocampus at 24 h after sepsis, associated with microglial, but not astrocyte, activation. MCC950 reduced oxidative damage to lipids and proteins as well as preserved the activity of the enzyme SOD in the hippocampus. Mitochondrial respiratory chain activity presented variations in both structures studied. MCC950 reduced microglial activation, decreased acute neurochemical and behavioral alteration, and increased survival after experimental sepsis.

Riding the tiger - physiological and pathological effects of superoxide and hydrogen peroxide generated in the mitochondrial matrix

Elevated mitochondrial matrix superoxide and/or hydrogen peroxide concentrations drive a wide range of physiological responses and pathologies. Concentrations of superoxide and hydrogen peroxide in the mitochondrial matrix are set mainly by rates of production, the activities of superoxide dismutase-2 (SOD2) and peroxiredoxin-3 (PRDX3), and by diffusion of hydrogen peroxide to the cytosol. These considerations can be used to generate criteria for assessing whether changes in matrix superoxide or hydrogen peroxide are both necessary and sufficient to drive redox signaling and pathology: is a phenotype affected by suppressing superoxide and hydrogen peroxide production; by manipulating the levels of SOD2, PRDX3 or mitochondria-targeted catalase; and by adding mitochondria-targeted SOD/catalase mimetics or mitochondria-targeted antioxidants? Is the pathology associated with variants in SOD2 and PRDX3 genes? Filtering the large literature on mitochondrial redox signaling using these criteria highlights considerable evidence that mitochondrial superoxide and hydrogen peroxide drive physiological responses involved in cellular stress management, including apoptosis, autophagy, propagation of endoplasmic reticulum stress, cellular senescence, HIF1α signaling, and immune responses. They also affect cell proliferation, migration, differentiation, and the cell cycle. Filtering the huge literature on pathologies highlights strong experimental evidence that 30-40 pathologies may be driven by mitochondrial matrix superoxide or hydrogen peroxide. These can be grouped into overlapping and interacting categories: metabolic, cardiovascular, inflammatory, and neurological diseases; cancer; ischemia/reperfusion injury; aging and its diseases; external insults, and genetic diseases. Understanding the involvement of mitochondrial matrix superoxide and hydrogen peroxide concentrations in these diseases can facilitate the rational development of appropriate therapies.

Pharmacological targeting of mitochondrial function and reactive oxygen species production prevents colon 26 cancer-induced cardiorespiratory muscle weakness

Cancer cachexia is a syndrome characterized by profound cardiac and diaphragm muscle wasting, which increase the risk of morbidity in cancer patients due to failure of the cardiorespiratory system. In this regard, muscle relies greatly on mitochondria to meet energy requirements for contraction and mitochondrial dysfunction can result in muscle weakness and fatigue. In addition, mitochondria are a major source of reactive oxygen species (ROS) production, which can stimulate increased rates of muscle protein degradation. Therefore, it has been suggested that mitochondrial dysfunction may be an underlying factor that contributes to the pathology of cancer cachexia. To determine if pharmacologically targeting mitochondrial dysfunction via treatment with the mitochondria-targeting peptide SS-31 would prevent cardiorespiratory muscle dysfunction, colon 26 (C26) adenocarcinoma tumor-bearing mice were administered either saline or SS-31 daily (3 mg/kg/day) following inoculation. C26 mice treated with saline demonstrated greater ROS production and mitochondrial uncoupling compared to C26 mice receiving SS-31 in both the heart and diaphragm muscle. In addition, saline-treated C26 mice exhibited a decline in left ventricular function which was significantly rescued in C26 mice treated with SS-31. In the diaphragm, muscle fiber cross-sectional area of C26 mice treated with saline was significantly reduced and force production was impaired compared to C26, SS-31-treated animals. Finally, ventilatory deficits were also attenuated in C26 mice treated with SS-31, compared to saline treatment. These data demonstrate that C26 tumors promote severe cardiac and respiratory myopathy, and that prevention of mitochondrial dysfunction is sufficient to preclude cancer cachexia-induced cardiorespiratory dysfunction.

Advances in characterization of SIRT3 deacetylation targets in mitochondrial function

The homeostasis of mitochondrial functional state is intimately in relation with SIRT3 (sirtuin3). SIRT3, the deacetylase mainly anchored in mitochondria, acts as a modulator of metabolic regulation via manipulating the activity and function of downstream targets at post-translational modification levels. The features of energy sensing and ADP-ribose transference of SIRT3 have also been reported. Recently, accumulating SIRT3-focusing evidences have suggested its complicated role in a series of adverse events such as metabolic disorders, aging-related diseases, coupled with tumors, in which SIRT3 regulates the progress of corresponding biochemical reactions by targeting key mediators. By systematically summarizing the downstream deacetylated proteins of the SIRT3 axis, this review aims to give a comprehensive introduction to the main metabolic pathways and diseases of the molecules involved in acetylation modification, which is expected to provide a direction for further exploration of the pathogenesis and therapeutic targets of the above diseases.

Nanotechnology-Based Diagnostics and Therapy for Pathogen-Related Infections in the CNS

The central nervous system (CNS) encompasses the brain, spinal cord, and nerves, where both brain and spinal cord are safeguarded by the meninges. However, serious bacterial, viral, or fungal infection in the brain causes life-threatening diseases such as meningitis. Engineered nanostructures hold great promise for not only in the diagnosis but also for combating microbial drug resistance owing to their high surface area and innate antibacterial activity. We delineate several nanoparticle-based approaches to enhance the CNS delivery of drugs across the blood-brain barrier (BBB). While pathogens invade the CNS by phagocytosis or receptor (e.g., EphA2)-mediated transcytosis, most of the nanoparticles cross the BBB via receptor-mediated transcytosis (e.g., antibody, peptide, protein). We also provide our perspectives on the diagnostic pathways based on nanotechnology for the detection of pathogens in the brain, thereby opening up new therapeutic avenues.

Elamipretide Attenuates Pyroptosis and Perioperative Neurocognitive Disorders in Aged Mice

Pyroptosis is a recently characterized inflammatory form of programmed cell death that is thought to be involved in the pathogenesis of perioperative neurocognitive disorders (PND). Elamipretide (SS-31), a mitochondrial-targeted peptide with multiple pharmacological properties, including anti-inflammatory activity, has been demonstrated to protect against many neurological diseases. However, the effect of elamipretide on pyroptosis in PND has not been studied. We established an animal model of PND by performing an exploratory laparotomy on mice under isoflurane anesthesia and examined the effects of elamipretide on cognitive function, synaptic integrity, neuroinflammation, mitochondrial function, and signaling controlling pyroptosis. Our results showed that anesthesia and surgery caused mitochondrial dysfunction and abnormal morphology, activation of canonicalnod-like receptor pyrin domain-containing 3 (NLRP3) inflammasome-caspase-1 dependent pyroptosis, and downregulation of synaptic integrity-related proteins in the hippocampus in aged mice, thus leading to learning and memory deficits in behavioral tests. Remarkably, treatment with the mitochondrial-targeted peptide elamipretide not only had protective effects against mitochondrial dysfunction but also attenuated surgery-induced pyroptosis and cognitive deficits. Our results provide a promising strategy for the treatment of PND involving mitochondrial dysfunction and pyroptosis.

Hydrogen attenuates sepsis-associated encephalopathy by NRF2 mediated NLRP3 pathway inactivation

OBJECTIVE

Sepsis-associated encephalopathy (SAE) is a major cause of mortality worldwide. Oxidative stress, inflammatory response and apoptosis participate in the pathogenesis of SAE. Nuclear factor erythroid 2-related factor 2 (Nrf2) and nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) pathway is involved in oxidative stress and inflammatory response. We reported that hydrogen gas protected against sepsis in wild-type (WT) but not Nrf2 knockout (KO) mice. Therefore, it is vital to identify the underlying cause of hydrogen gas treatment of sepsis-associated encephalopathy.

METHODS

SAE was induced in WT and Nrf2 KO mice by cecal ligation and puncture (CLP). As a NLRP3 inflammasome inhibitor, MCC950 (50 mg/kg) was administered by intraperitoneal (i.p.) injection before operation. Hydrogen gas (H₂)-rich saline solution (5 mL/kg) was administered by i.p. injection at 1 h and 6 h after sham and CLP operations. Brain tissue was collected to assess the NLRP3 and Nrf2 pathways by western blotting, reverse transcription-polymerase chain reaction (RT-PCR) and immunofluorescence.

RESULTS

SAE increased NLRP3 and Nrf2 expression in microglia. MCC950 inhibited SAE-induced NLRP3 expression, interleukin (IL)-1β and IL-18 cytokine release, neuronal apoptosis and mitochondrial dysfunction. SAE increased NLRP3 and caspase-1 expression in WT mice compared to Nrf2 KO mice. Hydrogen increased Nrf2 expression and inhibited the SAE-induced expression of NLRP3, caspase-1, cytokines IL-1β and IL-18, neuronal apoptosis, and mitochondrial dysfunction in WT mice but not Nrf2 KO mice.

CONCLUSION

SAE increased NLRP3 and Nrf2 expression in microglia. Hydrogen alleviated inflammation, neuronal apoptosis and mitochondrial dysfunction via inhibiting Nrf2-mediated NLRP3 pathway.

Curcumin ameliorates oxidative stress-induced intestinal barrier injury and mitochondrial damage by promoting Parkin dependent mitophagy through AMPK-TFEB signal pathway

The gut epithelial is known as the most critical barrier for protection against harmful antigens and pathogens. Oxidative stress has been implicated in the dysfunction of the intestine barrier. Hence, effective and safe therapeutic approaches for maintaining intestinal redox balance are urgently needed. Curcumin has gained attention for its vast beneficial biological function via antioxidative stress. However, whether the curcumin can relief intestine damage and mitochondrial injury induced by oxidative stress is still unclear. In this study, we found that curcumin can effectively ameliorate hydrogen peroxide (H₂O₂)-induced oxidative stress, intestinal epithelial barrier injury and mitochondrial damage in porcine intestinal epithelial cells (IPEC-J2 cells) in a PTEN-induced putative kinase (PINK1)-Parkin mitophagy dependent way. Mechanistically, depletion of Parkin (a mitophagy related protein) abolished curcumin's protective action on anti-oxidative stress, improving intestinal barrier and mitochondrial function in porcine intestinal epithelial cells (IPEC-J2) induced by H₂O₂. Consistently, the protective effect of curcumin was not found in cells transfected with GFP-ParkinΔUBL, which encodes a mutant Parkin protein without the ubiquitin E3 ligase activity, indicating that the ubiquitin E3 ligase of Parkin is required for curcumin's protective effects. On the other hand, we also found that the protective function of curcumin was diminished when PRKAA1 was depleted in IPEC-J2 cells treated with H₂O₂. Immunofluorescence and luciferase assay showed that curcumin dramatically enhanced nuclear translocation and transcriptional activity of transcription factor EB (TFEB) in IPEC-J2 cells treated with H₂O₂, and it was ameliorated by co-treated with compound C, an Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) inhibitor, which means curcumin promotes TFEB transcript via AMPK signal pathway. Consistent with in vitro data, dietary curcumin protected intestinal barrier function, improved redox status, alleviated mitochondrial damage, triggered mitophagy and influenced AMPK-TFEB signal pathway in a well-established pig oxidative stress model by challenging with diquat. Taken together, these results unveil that curcumin ameliorates oxidative stress, enhances intestinal barrier function and mitochondrial function via the induction of Parkin dependent mitophagy through AMPK activation and subsequent TFEB nuclear translocation.

Elamipretide (SS-31) improves mitochondrial dysfunction, synaptic and memory impairment induced by lipopolysaccharide in mice

Background

It is widely accepted that mitochondria have a direct impact on neuronal function and survival. Oxidative stress caused by mitochondrial abnormalities play an important role in the pathophysiology of lipopolysaccharide (LPS)-induced memory impairment. Elamipretide (SS-31) is a novel mitochondrion-targeted antioxidant. However, the impact of elamipretide on the cognitive sequelae of inflammatory and oxidative stress is unknown.

Methods

We utilized MWM and contextual fear conditioning test to assess hippocampus-related learning and memory performance. Molecular biology techniques and ELISA were used to examine mitochondrial function, oxidative stress, and the inflammatory response. TUNEL and Golgi-staining was used to detect neural cell apoptosis and the density of dendritic spines in the mouse hippocampus.

Results

Mice treated with LPS exhibited mitochondrial dysfunction, oxidative stress, an inflammatory response, neural cell apoptosis, and loss of dendritic spines in the hippocampus, leading to impaired hippocampus-related learning and memory performance in the MWM and contextual fear conditioning test. Treatment with elamipretide significantly ameliorated LPS-induced learning and memory impairment during behavioral tests. Notably, elamipretide not only provided protective effects against mitochondrial dysfunction and oxidative stress but also facilitated the regulation of brain-derived neurotrophic factor (BDNF) signaling, including the reversal of important synaptic-signaling proteins and increased synaptic structural complexity.

Conclusion

These findings indicate that LPS-induced memory impairment can be attenuated by the mitochondrion-targeted antioxidant elamipretide. Consequently, elamipretide may have a therapeutic potential in preventing damage from the oxidative stress and neuroinflammation that contribute to perioperative neurocognitive disorders (PND), which makes mitochondria a potential target for treatment strategies for PND.

SS-31 reduces inflammation and oxidative stress through the inhibition of Fis1 expression in lipopolysaccharide-stimulated microglia

SS-31 is a kind of mitochondrion-targeted peptide. Recent studies indicated significant neuroprotective effects of SS-31. In this study, we investigated that SS-31 protected the murine cultured microglial cells (BV-2) against lipopolysaccharide (LPS)-induced inflammation and oxidative stress through stabilizing mitochondrial morphology. The morphological study showed that SS-31 preserved LPS-induced mitochondrial ultrastructure by reducing the fission protein 1 (Fis1) expression. Flow cytometry and Western blot verified that SS-31 defended the BV-2 cells against LPS-stimulated inflammation and oxidative stress via suppressing Fis1. To sum up, our study represents that SS-31 preserves BV-2 cells from LPS-stimulated inflammation and oxidative stress by down-regulating the Fis1 expression.

Anti-inflammatory agent, OKN-007, reverses long-term neuroinflammatory responses in a rat encephalopathy model as assessed by multi-parametric MRI: implications for aging-associated neuroinflammation

Lipopolysaccharide (LPS)-induced encephalopathy induces neuroinflammation. Long-term neuroinflammation is associated with aging and subsequent cognitive impairment (CI). We treated rats that had LPS-induced neuroinflammation with OKN-007, with an anti-inflammatory agent currently considered an anti-cancer investigational new drug in clinical trials for glioblastoma (GBM). Contrast-enhanced magnetic resonance imaging (MRI) (CE-MRI), perfusion MRI, and MR spectroscopy were used as methods to assess long-term (up to 6 weeks post-LPS) alterations in blood-brain barrier (BBB) permeability, microvascularity, and metabolism, respectively, and the therapeutic effect of OKN-007. A free radical-targeted molecular MRI approach was also used to detect the effect of OKN-007 on brain free radical levels at 24 h and 1 week post-LPS injection. OKN-007 was able to reduce BBB permeability in the cerebral cortex and hippocampus at 1 week post-LPS using CE-MRI. OKN-007 was able to restore vascular perfusion rates by reducing LPS-induced increased relative cerebral blood flow (rCBF) in the cortex and hippocampus regions at all time points studied (1, 3, and 6 weeks post-LPS). OKN-007 was also able to restore LPS-induced brain metabolite depletions. NAA/Cho, Cr/Cho, and Myo-Ins/Cho metabolite ratios at 1, 3, and 6 weeks post-LPS were all restored to normal levels following OKN-007 treatment. OKN-007 also reduced LPS-induced free radical levels at 24 h and 1 week post-LPS, as detected by free radical-targeted MRI. LPS-exposed rats were compared with saline-treated controls and LPS + OKN-007-treated animals. We clearly demonstrated that OKN-007 restores LPS-induced BBB dysfunction, impaired vascularity, and decreased brain metabolites, all long-term neuroinflammatory indicators, as well as decreases free radicals in a LPS-induced neuroinflammation model. OKN-007 should be considered an anti-inflammatory agent for age-associated neuroinflammation.

Mitochondrial Dysfunction in Skeletal Muscle Pathologies

Several molecular mechanisms are involved in the regulation of skeletal muscle function. Among them, mitochondrial activity can be identified. The mitochondria is an important and essential organelle in the skeletal muscle that is involved in metabolic regulation and ATP production, which are two key elements of muscle contractibility and plasticity. Thus, in this review, we present the critical and recent antecedents regarding the mechanisms through which mitochondrial dysfunction can be involved in the generation and development of skeletal muscle pathologies, its contribution to detrimental functioning in skeletal muscle and its crosstalk with other typical signaling pathways related to muscle diseases. In addition, an update on the development of new strategies with therapeutic potential to inhibit the deleterious impact of mitochondrial dysfunction in skeletal muscle is discussed.

NLRP3/Caspase-1 Pathway-Induced Pyroptosis Mediated Cognitive Deficits in a Mouse Model of Sepsis-Associated Encephalopathy

Sepsis-associated encephalopathy (SAE) is a common complication that leads to long-term cognitive impairments and increased mortality in sepsis survivors. The mechanisms underlying this complication remain unclear and an effective intervention is lacking. Accumulating evidence suggests the nucleotide-binding domain-like receptor protein3 (NLRP3)/caspase-1 pathway is involved in several neurodegenerative diseases. Thus, we hypothesized that the NLRP3/caspase-1 pathway is involved in NLRP3-mediated pyroptosis, maturation and release of inflammatory cytokines, and cognitive deficits in SAE. We used the NLRP3 inhibitor MCC950 and the caspase-1 inhibitor Ac-YVAD-CMK to study the role of the NLRP3/caspase-1 pathway in pyroptosis and cognitive deficits in a mouse model of SAE. Mice were randomly assigned to one of six groups: sham+saline, sham+MCC950, sham+Ac-YVAD-CMK, cecal ligation and puncture (CLP)+saline, CLP+MCC950, and CLP+Ac-YVAD-CMK. Surviving mice underwent behavioral tests or had hippocampal tissues collected for histochemical analysis and biochemical assays. Our results show that CLP-induced hippocampus-dependent memory deficits are accompanied by increased NLRP3 and caspase-1 positive cells, and augmented protein levels of NLRP3, caspase-1, gasdermin-D, and pro-inflammatory cytokines in the hippocampus. In addition, administration of MCC950 or Ac-YVAD-CMK rescues cognitive deficits and ameliorates increased hippocampal NLRP3-mediated neuronal pyroptosis and pro-inflammatory cytokines. Our results suggest that the NLRP3/caspase-1 pathway-induced pyroptosis mediates cognitive deficits in a mouse model of SAE.

Systemic Inflammation Impairs Mood Function by Disrupting the Resting-State Functional Network in a Rat Animal Model Induced by Lipopolysaccharide Challenge

Background

Systemic inflammation impairs cognitive performance, yet the brain networks mediating this process remain to be elucidated. The purpose of the current study was to use resting-state functional magnetic resonance imaging (fMRI) to explore changes in the functional connectivity in a lipopolysaccharide- (LPS-) induced systemic inflammation animal model.

Materials and Methods

We used the regional homogeneity (ReHo) method to examine abnormal brain regions between the control and LPS groups and then considered them as seeds of functional connectivity analysis.

Results

Compared with the control group, our study showed that (1) LPS impaired mood function, as reflected by a depression-like behavior in the forced swim test; (2) LPS induced significantly increased ReHo values in the anterior cingulate cortex (ACC) and caudate putamen (CPu); (3) the ACC seed showed increased functional connectivity with the retrosplenial cortex, superior colliculus, and inferior colliculus; and (4) the right CPu seed showed increased functional connectivity with the left CPu. Linear regression analysis showed a LPS-induced depression-like behavior which was associated with increased ReHo values in the ACC and right CPu. Moreover, the LPS-induced depression-like behavior was related to increased functional connectivity between the right CPu and left CPu.

Conclusion

This is the first study to show that systemic inflammation impairs mood function that is associated with an altered resting-state functional network based on ReHo analysis, providing evidence of the abnormal regional brain spontaneous activity which might be involved in inflammation-related neurobehavioral abnormalities.

Progress in research on the role of Omi/HtrA2 in neurological diseases

Omi/HtrA2 is a serine protease present in the mitochondrial space. When stimulated by external signals, HtrA2 is released into the mitochondrial matrix where it regulates cell death through its interaction with apoptotic and autophagic signaling pathways. Omi/HtrA2 is closely related to the pathogenesis of neurological diseases, such as neurodegeneration and hypoxic ischemic brain damage. Here, we summarize the biological characteristics of Omi/HtrA2 and its role in neurological diseases, which will provide new hints in developing Omi/HtrA2 as a therapeutic target for neurological diseases.

Increased Survival Time With SS-31 After Prolonged Cardiac Arrest in Rats

BACKGROUND

Cardiac arrest is one of the leading causes of death with a very high mortality rate. No therapeutic drug that can be administered during resuscitation has been reported. Mitochondrial dysfunction is believed to play an important role for the pathogenesis of cardiac arrest. SS-31, a tetra-peptide, has been shown to protect mitochondria from ischaemia/reperfusion injury. Therefore, we tested whether SS-31 improves rat survival after prolonged cardiac arrest.

METHODS

Rats were randomised into two groups. After 25minutes of asphyxia-induced cardiac arrest, rats were resuscitated with or without SS-31 using cardiopulmonary bypass resuscitation. Rat survival was followed for additional 4.5hours using haemodynamic monitoring. The blood gas was analysed for surviving rats at multiple time points.

RESULTS AND CONCLUSIONS

After 5hours, 5 of 10 rats survived in the SS-31 group whereas only 1 of 10 rats survived in the control group (p=0.026). At 90minutes after resuscitation, the blood lactate level in the SS-31 treated rats (4.29±2.5mmol/L) was significantly lower than in control rats (7.36±3.1mmol/L, p=0.026), suggesting mitochondrial aerobic respiration was improved with SS-31 treatment. Overall, our data show the potential of SS-31 as a novel therapeutic in cardiac arrest.

Inhibiting the NLRP3 Inflammasome With MCC950 Ameliorates Isoflurane-Induced Pyroptosis and Cognitive Impairment in Aged Mice

Nod-like receptor protein 3 (NLRP3) inflammasome activation has been implicated in the pathogenesis of general anesthesia (GA)-induced neuroinflammation and cognitive impairment in aged rodents. However, the cellular basis for cognitive impairment is still not fully understood, and effective pharmacologic agents targeting the NLRP3 inflammasome during GA are lacking. This study explores the protective effects of the NLRP3 inflammasome inhibitor MCC950 on pyroptosis and cognitive impairment in aged mice exposed to isoflurane. Seventy-two 15-month-old male C57BL/6 mice were randomized to receive 2 h of 1.5% isoflurane plus 30% oxygen (O₂) or 30% O₂ alone, respectively. MCC950 (10 mg/kg) or vehicle was intraperitoneally administered 30 min before gas inhalation. Brain tissues were harvested for histochemical analysis and biochemical assays. Learning and memory abilities were evaluated by behavioral tests. We found that isoflurane GA caused upregulations of hippocampal NLRP3, cleaved caspase-1, interleukin-1β (IL-1β), and IL-18 and the activation of pyroptosis, which is NLRP3 inflammasome-dependent; this consequently gave rise to neuronal damage and cognitive impairment in aged mice. Interestingly, pretreatment with NLRP3 inflammasome inhibitor MCC950 not only provided a neuroprotective effect against the inflammasome activation but also ameliorated pyroptosis and cognitive impairment in aged mice exposed to isoflurane. Our data demonstrate that pyroptosis is involved in NLRP3 inflammasome-mediated isoflurane-induced cognitive impairment in aged mice and suggest that inhibiting the NLRP3 inflammasome with MCC950 may have clinically therapeutic benefits for elderly patients undertaking GA.

The mitochondrial antioxidant SS-31 increases SIRT1 levels and ameliorates inflammation, oxidative stress and leukocyte-endothelium interactions in type 2 diabetes

There is growing focus on mitochondrial impairment and cardiovascular diseases (CVD) in type 2 diabetes (T2D), and the development of novel therapeutic strategies in this context. It is unknown whether mitochondrial-targeting antioxidants such as SS-31 protect sufficiently against oxidative damage in diabetes. We aimed to evaluate if SS-31 modulates SIRT1 levels and ameliorates leukocyte-endothelium interactions, oxidative stress and inflammation in T2D patients. Anthropometric and metabolic parameters were studied in 51 T2D patients and 57 controls. Production of mitochondrial reactive oxygen species (ROS), mitochondrial membrane potential, glutathione content, leukocyte-endothelium interactions, NFκB-p65, TNFα and SIRT1 levels was measured in leukocytes treated or not with SS-31. We observed increased mitochondrial ROS production that was restored by SS-31 treatment. SS-31 also increased mitochondrial membrane potential, glutathione content, SIRT1 levels and leukocyte rolling velocity and reduced rolling flux and adhesion in T2D patients. NFκB-p65 and TNFα, which were enhanced in diabetic patients, were also reduced by SS-31 treatment. Our results reveal that SS-31 exerts beneficial effects on the leukocytes of T2D patients by reducing oxidative stress, leukocyte-endothelium interactions, NFκB and TNFα and by increasing SIRT1 levels. These actions support its use as a potential agent against CVD risk.