Chrysophanol suppresses pro-inflammatory response in microgliaviaregulation of Drp1-dependent mitochondrial fission

Drp1 and neuroinflammation: Deciphering the interplay between mitochondrial dynamics imbalance and inflammation in neurodegenerative diseases

Neuroinflammation and mitochondrial dysfunction are closely intertwined with the pathophysiology of neurological disorders. Recent studies have elucidated profound alterations in mitochondrial dynamics across a spectrum of neurological disorders. Dynamin-related protein 1 (DRP1) emerges as a pivotal regulator of mitochondrial fission, with its dysregulation disrupting mitochondrial homeostasis and fueling neuroinflammation, thereby exacerbating disease severity. In addition to its role in mitochondrial dynamics, DRP1 plays a crucial role in modulating inflammation-related pathways. This review synthesizes important functions of DRP1 in the central nervous system (CNS) and the impact of epigenetic modification on the progression of neurodegenerative diseases. The intricate interplay between neuroinflammation and DRP1 in microglia and astrocytes, central contributors to neuroinflammation, is expounded upon. Furthermore, the use of DRP1 inhibitors to influence the activation of microglia and astrocytes, as well as their involvement in processes such as mitophagy, mitochondrial oxidative stress, and calcium ion transport in CNS-mediated neuroinflammation, is scrutinized. The modulation of microglia to astrocyte crosstalk by DRP1 and its role in inflammatory neurodegeneration is also highlighted. Overall, targeting DRP1 presents a promising avenue for ameliorating neuroinflammation and enhancing the therapeutic management of neurological disorders.

A Review on Bioactive Anthraquinone and Derivatives as the Regulators for ROS

Anthraquinones are bioactive natural products, which are often found in medicinal herbs. These compounds exert antioxidant-related pharmacological actions including neuroprotective effects, anti-inflammation, anticancer, hepatoprotective effects and anti-aging, etc. Considering the benefits from their pharmacological use, recently, there was an upsurge in the development and utilization of anthraquinones as reactive oxygen species (ROS) regulators. In this review, a deep discussion was carried out on their antioxidant activities and the structure-activity relationships. The antioxidant mechanisms and the chemistry behind the antioxidant activities of both natural and synthesized compounds were furtherly explored and demonstrated. Due to the specific chemical activity of ROS, antioxidants are essential for human health. Therefore, the development of reagents that regulate the imbalance between ROS formation and elimination should be more extensive and rational, and the exploration of antioxidant mechanisms of anthraquinones may provide new therapeutic tools and ideas for various diseases mediated by ROS.

Targeting dynamin-related protein-1 as a potential therapeutic approach for mitochondrial dysfunction in Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease that manifests its pathology through synaptic damage, mitochondrial abnormalities, microRNA deregulation, hormonal imbalance, increased astrocytes & microglia, accumulation of amyloid β (Aβ) and phosphorylated Tau in the brains of AD patients. Despite extensive research, the effective treatment of AD is still unknown. Tau hyperphosphorylation and mitochondrial abnormalities are involved in the loss of synapses, defective axonal transport and cognitive decline in patients with AD. Mitochondrial dysfunction is evidenced by enhanced mitochondrial fragmentation, impaired mitochondrial dynamics, mitochondrial biogenesis and defective mitophagy in AD. Hence, targeting mitochondrial proteins might be a promising therapeutic strategy in treating AD. Recently, dynamin-related protein 1 (Drp1), a mitochondrial fission protein, has gained attention due to its interactions with Aβ and hyperphosphorylated Tau, altering mitochondrial morphology, dynamics, and bioenergetics. These interactions affect ATP production in mitochondria. A reduction in Drp1 GTPase activity protects against neurodegeneration in AD models. This article provides a comprehensive overview of Drp1's involvement in oxidative damage, apoptosis, mitophagy, and axonal transport of mitochondria. We also highlighted the interaction of Drp1 with Aβ and Tau, which may contribute to AD progression. In conclusion, targeting Drp1 could be a potential therapeutic approach for preventing AD pathology.

Chrysophanol exerts a protective effect against Aβ25-35-induced Alzheimer's disease model through regulating the ROS/TXNIP/NLRP3 pathway

BACKGROUND

The primary pathogenic factors of Alzheimer's disease (AD) have been identified as oxidative stress, inflammatory damage, and apoptosis. Chrysophanol (CHR) has a good neuroprotective effect on AD, however, the potential mechanism of CHR remains unclear.

PURPOSE

In this study, we focused on the ROS/TXNIP/NLRP3 pathway to determine whether CHR regulates oxidative stress and neuroinflammation.

METHODS

D-galactose and Aβ_25-35 combination were used to build an in vivo model of AD, and the Y-maze test was used to evaluate the learning and memory function of rats. Morphological changes of neurons in the rat hippocampus were observed using hematoxylin and eosin (HE) staining. AD cell model was established by Aβ_25-35 in PC12 cells. The DCFH-DA test identified reactive oxygen species (ROS). The apoptosis rate was determined using Hoechst33258 and flow cytometry. In addition, the levels of MDA, LDH, T-SOD, CAT, and GSH in serum, cell, and cell culture supernatant were detected by colorimetric method. The protein and mRNA expressions of the targets were detected by Western blot and RT-PCR. Finally, molecular docking was used to further verify the in vivo and in vitro experimental results.

RESULTS

CHR could significantly improve learning and memory impairment, reduce hippocampal neuron damage, and reduce ROS production and apoptosis in AD rats. CHR could improve the survival rate, and reduce the oxidative stress and apoptosis in the AD cell model. Moreover, CHR significantly decreased the levels of MDA and LDH, and increased the activities of T-SOD, CAT, and GSH in the AD model. Mechanically, CHR significantly reduced the protein and mRNA expression of TXNIP, NLRP3, Caspase-1, IL-1β, and IL-18, and increase TRX.

CONCLUSIONS

CHR exerts neuroprotective effects on the Aβ_25-35-induced AD model mainly by reducing oxidative stress and neuroinflammation, and the mechanism may be related to ROS/TXNIP/NLRP3 signaling pathway.

Mitochondrial dynamics in macrophages: divide to conquer or unite to survive?

Mitochondria have long been appreciated as the metabolic hub of cells. Emerging evidence also posits these organelles as hubs for innate immune signalling and activation, particularly in macrophages. Macrophages are front-line cellular defenders against endogenous and exogenous threats in mammals. These cells use an array of receptors and downstream signalling molecules to respond to a diverse range of stimuli, with mitochondrial biology implicated in many of these responses. Mitochondria have the capacity to both divide through mitochondrial fission and coalesce through mitochondrial fusion. Mitochondrial dynamics, the balance between fission and fusion, regulate many cellular functions, including innate immune pathways in macrophages. In these cells, mitochondrial fission has primarily been associated with pro-inflammatory responses and metabolic adaptation, so can be considered as a combative strategy utilised by immune cells. In contrast, mitochondrial fusion has a more protective role in limiting cell death under conditions of nutrient starvation. Hence, fusion can be viewed as a cellular survival strategy. Here we broadly review the role of mitochondria in macrophage functions, with a focus on how regulated mitochondrial dynamics control different functional responses in these cells.

Inhibition of Drp1-dependent mitochondrial fission by natural compounds as a therapeutic strategy for organ injuries

Mitochondria are morphologically dynamic organelles frequently undergoing fission and fusion processes that regulate mitochondrial integrity and bioenergetics. These processes are considered critical for cell survival. The mitochondrial fission process regulates mitochondrial biogenesis and mitophagy. It is associated with apoptosis, while mitochondrial fusion controls the accurate distribution of mitochondrial DNA and metabolic substances across the mitochondria. Excessive mitochondrial fission results in mitochondrial structural changes, dysfunction, and cell damage. Accumulating evidence demonstrates that mitochondrial dynamics affect neurodegenerative and cardiovascular diseases along with several other diseases. Biological molecules regulating the process of mitochondrial fission are potential targets for developing therapeutic agents. Many natural products target the dynamin-related protein 1 (Drp1)-dependent mitochondrial fission pathway, and their inhibitory effects ameliorate mitochondrial fragmentation. In this article, we reviewed the research literature that describes Drp1-dependent inhibition as a mechanism for the protective effects of natural compounds.

Neuroprotective Strategies for Stroke by Natural Products: Advances and Perspectives

Cerebral ischemic stroke is a disease with high prevalence and incidence. Its management focuses on rapid reperfusion with intravenous thrombolysis and endovascular thrombectomy. Both therapeutic strategies reduce disability, but the therapy time window is short, and the risk of bleeding is high. Natural products (NPs) have played a key role in drug discovery, especially for cancer and infectious diseases. However, they have made little progress in clinical translation and pose challenges to the treatment of stroke. Recently, with the investigation of precise mechanisms in cerebral ischemic stroke and the technological development of NP-based drug discovery, NPs are addressing these challenges and opening up new opportunities in cerebral stroke. Thus, in this review, we first summarize the structure and function of diverse NPs, including flavonoids, phenols, terpenes, lactones, quinones, alkaloids, and glycosides. Then we propose the comprehensive neuroprotective mechanism of NPs in cerebral ischemic stroke, which involves complex cascade processes of oxidative stress, mitochondrial damage, apoptosis or ferroptosis-related cell death, inflammatory response, and disruption of the blood-brain barrier (BBB). Overall, we stress the neuroprotective effect of NPs and their mechanism on cerebral ischemic stroke for a better understanding of the advances and perspective in NPs application that may provide a rationale for the development of innovative therapeutic regimens in ischemic stroke.

Parkinson's disease: connecting mitochondria to inflammasomes

Activated microglia foster a neurotoxic, inflammatory environment in the mammalian central nervous system (CNS) that drives the pathology of neurodegenerative diseases including Parkinson's disease (PD). Moreover, mitochondrial fission promotes microglial inflammatory responses in vitro. Given that the NLRP3 inflammasome and mitochondria are central regulators of both inflammation and PD, we explore potential functions for the NLRP3 inflammasome and mitochondrial dynamics in PD. Specifically, we propose that inducible microglial mitochondrial fission can promote NLRP3-dependent neuroinflammation in hereditary and idiopathic PD. Further in-depth exploration of this topic can prompt valuable discoveries of the underlying molecular mechanisms of PD neuroinflammation, identify novel candidate anti-inflammatory therapeutics for PD, and ideally provide better outcomes for PD patients.

Chrysophanol facilitates long-term neurological recovery through limiting microglia-mediated neuroinflammation after ischemic stroke in mice

BACKGROUND

Inflammation plays an important role in ischemic brain injury and affects brain recovery and neuroplasticity. Chrysophanol (CHR), has attracted attention for its protective effects through immunomodulatory and anti-inflammatory properties. However, the effect of CHR for brain recovery and neuroplasticity is not clear. The current study aimed to investigate the effect of CHR in the chronic phase of stroke in mice, and to elucidate the underlying mechanisms.

METHODS

C57BL/6 mice were subjected to treatment with Vehicle or CHR immediately through intraperitoneal injection daily for 14 d after distal middle cerebral artery occlusion (dMCAO). Neurological deficits were monitored up to 28 days after stroke. Nissl and Golgi stain, neural plasticity, and microglia-associated inflammatory cytokines were detected. Primary cortical neuron and BV2 microglia cell lines were employed to explore the underlying mechanism in vitro.

RESULTS

Compared with Vehicle group, CHR mitigated the histological damage, facilitated the neural plasticity and improved the neurological function up to 4 weeks after stroke. In vitro, CHR promoted the complexity of neurons and the spine density by modulating microglial polarization and reducing the expression of microglia-associated inflammatory cytokines, especially IL-6. In vivo, microglia activation and inflammatory cytokines were significantly increased after dMCAO and downregulated by CHR. Further investigation showed STAT3 is the major downstream effector of IL-6 signaling.

CONCLUSIONS

CHR ameliorated microenvironment for neural plasticity and exhibited neuroprotection via arresting microglia toward pro-inflammatory phenotype and downregulation of the expressions of pro-inflammatory cytokines, especially of IL-6. IL-6-STAT3 signaling might be CHR's therapeutic target for neuroinflammatory responses after stroke.

Chrysophanol exerts neuroprotective effects via interfering with endoplasmic reticulum stress apoptotic pathways in cell and animal models of Alzheimer's disease

OBJECTIVES

Chrysophanol (CHR), also well-known as Rhei radix et rhizome, is a crucial component in traditional Chinese medicine. It has been widely studied as a potential treatment for many diseases due to its anti-inflammatory effects. However, there are very few studies to establish the potential therapeutic effect of CHR in cell and animal models of Alzheimer's disease (AD). Therefore, we aim to investigate whether CHR could be used as a potential therapeutic approach to patients with AD and further disclose the underlying mechanism. Increasing studies have shown that endoplasmic reticulum (ER) calcium (Ca2+) homeostasis emerges as a central player in AD pathogenesis. Moreover, augmentation of ER stress (ERS) promotes neuronal apoptosis, and excessive oxidative stress is an inducer of ERS. Therefore, we believe that ERS-mediated apoptosis may be one of the causes of AD.

METHODS

This study examined the neuroprotective effects of CHR on AD rats and AD cell models and explored its potential mechanism.

KEY FINDINGS

CHR could reduce the damage of neurons. In AD cell models, CHR significantly inhibited Aβ 25-35-induced neuronal damage, reduced the number of apoptotic cells and improved cell survival rate. Western blot showed that the expression of caspases 3, 9 and 12 was decreased after CHR treatment, and CHR also affected the ERS signalling pathway. In addition, the higher expression of pro-apoptotic proteins in the AD cell model was reduced after CHR treatment by inhibiting GRP78 signalling. Further studies have shown that overexpressed protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK) inhibited the regulatory effect of CHR on PERK and weakened the neuroprotective effect of CHR on the AD cell model.

CONCLUSIONS

This study revealed a novel mechanism through which CHR plays a neuroprotective role by regulating ERS when it comes to the therapy of AD.

Psoriasiform Inflammation Is Associated with Mitochondrial Fission/GDAP1L1 Signaling in Macrophages

While psoriasis is known as a T cell- and dendritic cell-driven skin inflammation disease, macrophages are also reported to play some roles in its development. However, the signaling pathway of activated macrophages contributing to psoriasis is not entirely understood. Thus, we aimed to explore the possible mechanisms of how macrophages initiate and sustain psoriasis. The differentiated THP1 cells, stimulated by imiquimod (IMQ), were utilized as the activated macrophage model. IMQ was also employed to produce psoriasis-like lesions in mice. A transcriptomic assay of macrophages revealed that the expressions of pro-inflammatory mediators and GDAP1L1 were largely increased after an IMQ intervention. The depletion of GDAP1L1 by short hairpin (sh)RNA could inhibit cytokine release by macrophages. GDAP1L1 modulated cytokine production by activating the phosphorylation of mitogen-activated protein kinases (MAPKs) and nuclear factor (NF)-κB pathways. Besides GDAP1L1, another mitochondrial fission factor, Drp1, translocated from the cytosol to mitochondria after IMQ stimulation, followed by the mitochondrial fragmentation according to the immunofluorescence imaging. Clodronate liposomes were injected into the mice to deplete native macrophages for examining the latter’s capacity on IMQ-induced inflammation. The THP1 cells, with or without GDAP1L1 silencing, were then transplanted into the mice to monitor the deposition of macrophages. We found a significant THP1 accumulation in the skin and lymph nodes. The silencing of GDAP1L1 in IMQ-treated animals reduced the psoriasiform severity score from 8 to 2. After depleting GDAP1L1, the THP1 recruitment in the lymph nodes was decreased by 3-fold. The skin histology showed that the GDAP1L1-mediated macrophage activation induced neutrophil chemotaxis and keratinocyte hyperproliferation. Thus, mitochondrial fission can be a target for fighting against psoriatic inflammation.

Chrysophanol Protects Against Acute Heart Failure by Inhibiting JNK1/2 Pathway in Rats

BACKGROUND Acute heart failure (AHF) usually requires urgent therapy. Myocardial damage, oxidative stress, and inflammation are major components in the pathology of AHF. This study was designed to investigate the effects of chrysophanol on AHF. MATERIAL AND METHODS Sprague-Dawley rats were injected with isoprenaline hydrochloride to construct AHF rat models. AHF rats were treated with normal saline (negative control), chrysophanol, the combination of chrysophanol and SP600125, or benazepril (positive control) using sham rats as blank controls. Echocardiography, histological staining, and enzyme activity analysis were performed to assess the heart functions and myocardial damage. Effects on apoptosis, oxidative stress (OS), and inflammation were evaluated by biochemical analysis, TUNEL staining, and ELISA. RESULTS Chrysophanol improved the parameters of cardiac functions and alleviated the myocardial damage accompanied by the reduction of creatine kinase and lactate dehydrogenase activity. Meanwhile, chrysophanol inhibited the myocardial apoptosis along with the upregulation of Bcl-2 and downregulation of Bax and cleaved caspase-3. AHF-induced abnormal changes of OS parameters (MDA, GPx, CAT, SOD) and inflammatory markers (IL-6, IL-1ß, TNF-alpha, IFN-γ) were alleviated by chrysophanol. Benazepril treatment showed similar results with chrysophanol, while the addition of SP600125 enhanced the chrysophanol-mediated protection effects in AHF rats. Western blot analysis demonstrated that chrysophanol inhibited the phosphorylation of JNK1/2 and its upstream/downstream factors. CONCLUSIONS Chrysophanol improved cardiac functions and protected against myocardial damage, apoptosis, OS, and inflammation by inhibiting activation of the JNK1/2 pathway in AHF rat models. These finding indicate that chrysophanol may be a promising approach for treatment of AHF.

Muscone relieves inflammatory pain by inhibiting microglial activation-mediated inflammatory response via abrogation of the NOX4/JAK2-STAT3 pathway and NLRP3 inflammasome

Previous studies have shown that muscone, a pharmacologically active ingredient isolated from musk, has excellent effects on anti-inflammation. However, its effect on microglia activation-induced inflammatory pain is not known yet. In the present study, a mouse BV2 microglia cell activation-mediated inflammatory model was developed with LPS induction, and a mouse inflammatory pain model was established with CFA injection. The inhibitory effect of muscone on microglia inflammatory activation was verified by measuring pro-inflammatory cytokines expression (interleukin-6, tumor necrosis factor-α, and interleukin-1β; IL-6, TNF-α and IL-1β). We found that muscone suppressed microglial activation-mediated inflammatory response through the NADPH oxidase 4 (NOX4)/janus kinase 2-signal transducer and activator of transcription 3 (JAK2-STAT3) pathway and pyrin-domain-containing 3 (NLRP3) inflammasome. Notably, muscone mitigated CFA-induced pain hypersensitivity and inflammation, as well as microglia cell activation in vivo. Furthermore, muscone inhibited the CFA-induced NOX4, p-JAK2/p-STAT3, and NLRP3 inflammasome expression in spinal cord of mice. In conclusion, this study uncovered that muscone relieved inflammatory pain by inhibiting microglial activation-mediated inflammatory response via abrogation of the NOX4/JAK2-STAT3 pathway and NLRP3 inflammasome. This finding of muscone is promising for treating inflammatory pain.

Chrysophanol improves memory ability of d-galactose and Aβ25-35 treated rat correlating with inhibiting tau hyperphosphorylation and the CaM-CaMKIV signal pathway in hippocampus

This study was aimed to investigate the effect of Chrysophanol (CHR) on Alzheimer's disease. We also attempted to understand the potential mechanisms. An Alzheimer's disease rat model was established using an intraperitoneal injection of d-galactose combined with an intracerebral injection of amyloid-β peptide (25-35), and the effect of CHR on the learning and memory ability, the hippocampal neurons change, the ultrastructure of the hippocampal CA1 region, the protein levels of CaM, CaMKK, CaMKIV, p-CaMKIV and p-tau in the hippocampus of rats were studied. The results showed that CHR significantly improved the cognitive deficits, alleviated hippocampal neurons damage, prevented the ultrastructure alteration of neurons in hippocampal CA1 region, and reduced the protein levels of CaM, CaMKK, p-CaMKIV and p-tau in the hippocampus of AD rats. These results suggested that Chrysophanol could improve memory ability of Alzheimer's disease rat by inhibiting tau hyperphosphorylation and the CaM-CaMKIV signal pathway.

HuoXueTongFu Formula Alleviates Intraperitoneal Adhesion by Regulating Macrophage Polarization and the SOCS/JAK2/STAT/PPAR-γ Signalling Pathway

Intraperitoneal adhesion is a common complication after abdominal surgery, which seriously affects the quality of life of patients. HuoXueTongFu Formula (HXTF) plays an important role in the prevention and treatment of intraperitoneal adhesions. However, the molecular-related mechanisms are still not fully known. In this study, the model of Intrapetitoneal adhesion was established by cecum abrasion and treated with HXTF for one week. RAW264.7 cells were given LPS, IFN-γ, IL-4, HXTF-medicated serum, and PPAR-γ agonist/antagonist, respectively. Histopathology, flow cytometry, ELISA, real-time PCR, and Western blotting were used to further detect the related protein, M1/M2 polarization tendency, and PPAR-γ nuclear translocation. The deposition of collagen fibres reduced in the local area of rats after the operation with HXTF treatment. Similar to IL-4, HXTF induced a tendency for macrophages to polarize toward M2 and promoted peroxisome proliferator-activated receptor-gamma (PPAR-γ) nuclear translocation. Furthermore, the use of HXTF and PPAR-γ agonists downregulated macrophage M1 polarization-related factors IL-1, IL-6, and TNF-alpha and upregulated M2 polarization-related factors IL-4, IL-10, and TGF-beta 1. Meanwhile, the use of HXTF and PPAR-γ agonists downregulated the SOCS3/JAK2/STAT1 pathway and activated the SOCS1/STAT6/PPAR-γ pathway. These results show that HXTF may reduce intraperitoneal adhesion by inducing macrophage M2 polarization and regulating the SOCS/JAK2/STAT/PPAR-γ pathway.

Chrysophanol: a review of its pharmacology, toxicity and pharmacokinetics

OBJECTIVE

Chrysophanol is a natural anthraquinone, also known as chrysophanic acid and 1,8-dihydroxy-3-methyl-anthraquinone. It has been widely used in the food and pharmaceutical fields. This review is intended to provide a comprehensive overview of the pharmacology, toxicity and pharmacokinetic researches of chrysophanol.

KEY FINDING

Information on chrysophanol was collected from the Internet database PubMed, Elsevier, ResearchGate, Web of Science, Wiley Online Library and Europe PM using a combination of keywords including 'pharmacology', 'toxicology' and 'pharmacokinetics'. The literature we collected included from January 2010 to June 2019. Chrysophanol has a wide spectrum of pharmacological effects, including anticancer, antioxidation, neuroprotection, antibacterial and antiviral, and regulating blood lipids. However, chrysophanol has obvious hepatotoxicity and nephrotoxicity, and pharmacokinetics indicate that the use of chrysophanol in combination with other drugs can reduce toxicity and enhance efficacy.

SUMMARY

Chrysophanol can be used in many diseases. Future research directions include how the concentration of chrysophanol affects pharmacological effects and toxicity; the mechanism of synergy between chrysophanol and other drugs.

Demonstration of prion-like properties of mutant huntingtin fibrils in both in vitro and in vivo paradigms

In recent years, evidence has accumulated to suggest that mutant huntingtin protein (mHTT) can spread into healthy tissue in a prion-like fashion. This theory, however, remains controversial. To fully address this concept and to understand the possible consequences of mHTT spreading to Huntington’s disease pathology, we investigated the effects of exogenous human fibrillar mHTT (Q48) and huntingtin (HTT) (Q25) N-terminal fragments in three cellular models and three distinct animal paradigms. For in vitro experiments, human neuronal cells [induced pluripotent stem cell-derived GABA neurons (iGABA) and (SH-SY5Y)] as well as human THP1-derived macrophages, were incubated with recombinant mHTT fibrils. Recombinant mHTT and HTT fibrils were taken up by all cell types, inducing cell morphology changes and death. Variations in HTT aggregation were further observed following incubation with fibrils in both THP1 and SH-SY5Y cells. For in vivo experiments, adult wild-type (WT) mice received a unilateral intracerebral cortical injection and R6/2 and WT pups were administered fibrils via bilateral intraventricular injections. In both protocols, the injection of Q48 fibrils resulted in cognitive deficits and increased anxiety-like behavior. Post-mortem analysis of adult WT mice indicated that most fibrils had been degraded/cleared from the brain by 14 months post-surgery. Despite the absence of fibrils at these later time points, a change in the staining pattern of endogenous HTT was detected. A similar change was revealed in post-mortem analysis of the R6/2 mice. These effects were specific to central administration of fibrils, as mice receiving intravenous injections were not characterized by behavioral changes. In fact, peripheral administration resulted in an immune response mounting against the fibrils. Together, the in vitro and in vivo data indicate that exogenously administered mHTT is capable of both causing and exacerbating disease pathology.

Ca2+/calmodulin-dependent protein kinase II regulation by inhibitor 1 of protein phosphatase 1 alleviates necroptosis in high glucose-induced cardiomyocytes injury

Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) plays an important role in the cardiovascular system. However, the potential protective role of inhibitor 1 of protein phosphatase 1 (I1PP1), which is able to regulate CaMKII, in high glucose-induced cardiomyocytes injury remains unknown. In the present study, cardiomyocytes were transfected with I1PP1 adenovirus to inhibit protein phosphatase 1 (PP1) expression. After the cardiomyocytes were subjected to high glucose stimulation for 48 h, quantitative real-time PCR was used to detect CaMKIIδ alternative splicing. Lactate dehydrogenase (LDH) release and adenosine triphosphate (ATP) level were measured to assess cell damage and energy metabolism respectively. CaMKII activity was represented as phospholamban (PLB) phosphorylation, CaMKII phosphorylation (p-CaMKII) and oxidation (ox-CaMKII). Dihydroethidium (DHE), MitoSOX and JC-1 staining were used to assess oxidative stress and mitochondrial membrane potential. Necroptosis was evaluated by receptor interacting protein kinase 3 (RIPK3) expression, TUNEL and cleaved-caspase 3 levels. RIPK3, mixed lineage kinase domain like protein (MLKL) and dynamin-related protein 1 (DRP1) expressions were also detected. We found that high glucose disordered CaMKIIδ alternative splicing. I1PP1 over-expression suppressed PLB phosphorylation, ox-CaMKII, DRP1, RIPK3 and cleaved-caspase 3 proteins expression, decreased LDH release, attenuated necroptosis, increased ATP level, inhibited oxidative stress, and elevated mitochondrial membrane potential in high glucose-stimulated cardiomyocytes. However, there was no effect on phosphorylation of MLKL (p-MLKL), p-CaMKII, and receptor interacting protein kinase 1 (RIPK1) expression. Altogether, I1PP1 over-expression alleviated CaMKIIδ alternative splicing disorder, suppressed CaMKII oxidation, reduced reactive oxygen species (ROS) accumulation and inhibited necroptosis to attenuate high glucose-induced cardiomyocytes injury.

LRRK2 Kinase Activity Induces Mitochondrial Fission in Microglia via Drp1 and Modulates Neuroinflammation

Leucine-rich repeat kinase 2 (LRRK2) mutations are the most common genetic cause of Parkinson's disease (PD). LRRK2 contains a functional kinase domain and G2019S, the most prevalent LRRK2 pathogenic mutation, increases its kinase activity. LRRK2 regulates mitochondria morphology and autophagy in neurons. LPS treatment increases LRRK2 protein level and mitochondrial fission in microglia, and down-regulation of LRRK2 expression or inhibition of its kinase activity attenuates microglia activation. Here, we evaluated the direct role of LRRK2 G2019S in mitochondrial dynamics in microglia. Initial observation of microglia in G2019S transgenic mice revealed a decrease in mitochondrial area and shortage of microglial processes compared with their littermates. Next, we elucidated the molecular mechanisms of these phenotypes. Treatment of BV2 cells and primary microglia with LPS enhanced mitochondrial fission and increased Drp1, a mitochondrial fission marker, as previously reported. Importantly, both phenotypes were rescued by treatment with GSK2578215A, a LRRK2 kinase inhibitor. Finally, the protein levels of CD68, an active microglia marker, Drp1 and TNF-α were significantly higher in brain lysates of G2019S transgenic mice compared with the levels in their littermates. Taken together, our data suggest that LRRK2 could promote microglial mitochondrial alteration via Drp1 in a kinase-dependent manner, resulting in stimulation of pro-inflammatory responses. This mechanism in microglia might be a potential target to develop PD therapy since neuroinflammation by active microglia is a major symptom of PD.