Somatostatin prevents lipopolysaccharide-induced neurodegeneration in the rat substantia nigra by inhibiting the activation of microglia

Deciphering the molecular pathways underlying dopaminergic neuronal damage in Parkinson's disease associated with SARS-CoV-2 infection

BACKGROUND

The COVID-19 pandemic caused by SARS-CoV-2 has led to significant global morbidity and mortality, with potential neurological consequences, such as Parkinson's disease (PD). However, the underlying mechanisms remain elusive.

METHODS

To address this critical question, we conducted an in-depth transcriptome analysis of dopaminergic (DA) neurons in both COVID-19 and PD patients. We identified common pathways and differentially expressed genes (DEGs), performed enrichment analysis, constructed protein‒protein interaction networks and gene regulatory networks, and employed machine learning methods to develop disease diagnosis and progression prediction models. To further substantiate our findings, we performed validation of hub genes using a single-cell sequencing dataset encompassing DA neurons from PD patients, as well as transcriptome sequencing of DA neurons from a mouse model of MPTP(1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-induced PD. Furthermore, a drug-protein interaction network was also created.

RESULTS

We gained detailed insights into biological functions and signaling pathways, including ion transport and synaptic signaling pathways. CD38 was identified as a potential key biomarker. Disease diagnosis and progression prediction models were specifically tailored for PD. Molecular docking simulations and molecular dynamics simulations were employed to predict potential therapeutic drugs, revealing that genistein holds significant promise for exerting dual therapeutic effects on both PD and COVID-19.

CONCLUSIONS

Our study provides innovative strategies for advancing PD-related research and treatment in the context of the ongoing COVID-19 pandemic by elucidating the common pathogenesis between COVID-19 and PD in DA neurons.

Role of microglial metabolic reprogramming in Parkinson's disease

Parkinson's disease (PD) is a common age-related neurodegenerative disorder characterized by damage to nigrostriatal dopaminergic neurons. Key pathogenic mechanisms underlying PD include alpha-synuclein misfolding and aggregation, impaired protein clearance, mitochondrial dysfunction, oxidative stress, and neuroinflammation. However, to date, no study has confirmed the specific pathogenesis of PD. Similarly, current PD treatment methods still have shortcomings. Although some emerging therapies have proved effective for PD, the specific mechanism still needs further clarification. Metabolic reprogramming, a term first proposed by Warburg, is applied to the metabolic energy characteristics of tumor cells. Microglia have similar metabolic characteristics. Pro-inflammatory M1 type and anti-inflammatory M2 type are the two types of activated microglia, which exhibit different metabolic patterns in glucose, lipid, amino acid, and iron metabolism. Additionally, mitochondrial dysfunction may be involved in microglial metabolic reprogramming by activating various signaling mechanisms. Functional changes in microglia resulting from metabolic reprogramming can cause changes in the brain microenvironment, thus playing an important role in neuroinflammation or tissue repair. The involvement of microglial metabolic reprogramming in PD pathogenesis has been confirmed. Neuroinflammation and dopaminergic neuronal death can effectively be reduced by inhibiting certain metabolic pathways in M1 microglia or reverting M1 cells to the M2 phenotype. This review summarizes the relationship between microglial metabolic reprogramming and PD and provides strategies for PD treatment.

Regional heterogeneity in mitochondrial function underlies region specific vulnerability in human brain ageing: Implications for neurodegeneration

Selective neuronal vulnerability (SNV) of specific neuroanatomical regions such as frontal cortex (FC) and hippocampus (HC) is characteristic of age-associated neurodegenerative diseases (NDDs), although its pathogenetic basis remains unresolved. We hypothesized that physiological differences in mitochondrial function in neuroanatomical regions could contribute to SNV. To investigate this, we evaluated mitochondrial function in human brains (age range:1-90 y) in FC, striatum (ST), HC, cerebellum (CB) and medulla oblongata (MD), using enzyme assays and quantitative proteomics. Striking differences were noted in resistant regions- MD and CB compared to the vulnerable regions- FC, HC and ST. At younger age (25 ± 5 y), higher activity of electron transport chain enzymes and upregulation of metabolic and antioxidant proteins were noted in MD compared to FC and HC, that was sustained with increasing age (≥65 y). In contrast, the expression of synaptic proteins was higher in FC, HC and ST (vs. MD). In line with this, quantitative phospho-proteomics revealed activation of upstream regulators (ERS, PPARα) of mitochondrial metabolism and inhibition of synaptic pathways in MD. Microtubule Associated Protein Tau (MAPT) showed overexpression in FC, HC and ST both in young and older age (vs. MD). MAPT hyperphosphorylation and the activation of its kinases were noted in FC and HC with age. Our study demonstrates that regional heterogeneity in mitochondrial and other cellular functions contribute to SNV and protect regions such as MD, while rendering FC and HC vulnerable to NDDs. The findings also support the "last in, first out" hypothesis of ageing, wherein regions such as FC, that are the most recent to develop phylogenetically and ontogenetically, are the first to be affected in ageing and NDDs.

Lipidomics of Bioactive Lipids in Alzheimer's and Parkinson's Diseases: Where Are We?

Lipids are not only constituents of cellular membranes, but they are also key signaling mediators, thus acting as “bioactive lipids”. Among the prominent roles exerted by bioactive lipids are immune regulation, inflammation, and maintenance of homeostasis. Accumulated evidence indicates the existence of a bidirectional relationship between the immune and nervous systems, and lipids can interact particularly with the aggregation and propagation of many pathogenic proteins that are well-renowned hallmarks of several neurodegenerative disorders, including Alzheimer’s (AD) and Parkinson’s (PD) diseases. In this review, we summarize the current knowledge about the presence and quantification of the main classes of endogenous bioactive lipids, namely glycerophospholipids/sphingolipids, classical eicosanoids, pro-resolving lipid mediators, and endocannabinoids, in AD and PD patients, as well as their most-used animal models, by means of lipidomic analyses, advocating for these lipid mediators as powerful biomarkers of pathology, diagnosis, and progression, as well as predictors of response or activity to different current therapies for these neurodegenerative diseases.

Demystifying the Neuroprotective Role of Neuropeptides in Parkinson's Disease: A Newfangled and Eloquent Therapeutic Perspective

Parkinson's disease (PD) refers to one of the eminently grievous, preponderant, tortuous nerve-cell-devastating ailments that markedly impacts the dopaminergic (DArgic) nerve cells of the midbrain region, namely the substantia nigra pars compacta (SN-PC). Even though the exact etiopathology of the ailment is yet indefinite, the existing corroborations have suggested that aging, genetic predisposition, and environmental toxins tremendously influence the PD advancement. Additionally, pathophysiological mechanisms entailed in PD advancement encompass the clumping of α-synuclein inside the lewy bodies (LBs) and lewy neurites, oxidative stress, apoptosis, neuronal-inflammation, and abnormalities in the operation of mitochondria, autophagy lysosomal pathway (ALP), and ubiquitin-proteasome system (UPS). The ongoing therapeutic approaches can merely mitigate the PD-associated manifestations, but until now, no therapeutic candidate has been depicted to fully arrest the disease advancement. Neuropeptides (NPs) are little, protein-comprehending additional messenger substances that are typically produced and liberated by nerve cells within the entire nervous system. Numerous NPs, for instance, substance P (SP), ghrelin, neuropeptide Y (NPY), neurotensin, pituitary adenylate cyclase-activating polypeptide (PACAP), nesfatin-1, and somatostatin, have been displayed to exhibit consequential neuroprotection in both in vivo and in vitro PD models via suppressing apoptosis, cytotoxicity, oxidative stress, inflammation, autophagy, neuronal toxicity, microglia stimulation, attenuating disease-associated manifestations, and stimulating chondriosomal bioenergetics. The current scrutiny is an effort to illuminate the neuroprotective action of NPs in various PD-experiencing models. The authors carried out a methodical inspection of the published work procured through reputable online portals like PubMed, MEDLINE, EMBASE, and Frontier, by employing specific keywords in the subject of our article. Additionally, the manuscript concentrates on representing the pathways concerned in bringing neuroprotective action of NPs in PD. In sum, NPs exert substantial neuroprotection through regulating paramount pathways indulged in PD advancement, and consequently, might be a newfangled and eloquent perspective in PD therapy.

Protective effects of endotoxin tolerance on peripheral lipopolysaccharide-induced neuroinflammation and dopaminergic neuronal injury

CONTEXT

Parkinson's disease is a common chronic neurodegenerative disease characterized by massive loss of dopaminergic neurons in the substantia nigra. Neuroinflammation has been shown to play an important role in the pathogenesis of neurodegenerative diseases such as Parkinson's disease. The role of immune tolerance in neuroinflammation and neurodegenerative diseases induced by peripheral factors is unclear.

OBJECTIVE

This study established a model of endotoxin tolerance to explore the protective effect of endotoxin tolerance on Parkinson-like changes induced by repeated peripheral injections of high-dose LPS, and to explore its inflammatory mechanism.

MATERIALS AND METHODS

In this study, mice were injected intraperitoneally with low dose (0.5 mg/kg) LPS for 4 days to induce endotoxin tolerance (ET). Then, high-dose (1 mg/kg) LPS was injected continuously intraperitoneally for 4 days to induce Parkinson-like changes. Cytokines were detected by enzyme-linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qRT-PCR). Activation of microglial cells was detected by protein expression of CD68 and ionized calcium binding adapter molecule 1(Iba-1) by Western blotting and immunofluorescence. Hematoxylin and eosin staining and expression of tyrosine hydroxylase (TH) and dopamine (DA) were used to assess dopaminergic neuronal injury. The open field test and muscle tension test were used to assess behavioral disorders.

RESULTS

As expected, compared with non-ET animals, ET preconditioning significantly reduced the production of inflammatory cytokines in the substantia nigra, inhibited microglial activation, and alleviated the pathological changes of dopaminergic neurons.

CONCLUSIONS

ET may be a promising intervention method for neurodegenerative diseases.HighlightsET was successfully induced by continuous low-dose intraperitoneal LPS injection in mice.ET pretreatment inhibited neuroinflammation in the SN induced by continuous peripheral high doses of LPS.ET pretreatment inhibited continuous peripheral high-dose LPS injection-induced microglial activation in the SN.ET pretreatment decreased LPS-induced functional impairment of dopaminergic neurons.ET reversed the morphological changes of dopaminergic neurons induced by peripheral high-dose LPS.ET pretreatment improved continuous peripheral high-dose LPS injection-induced behavioral impairment.

Novel Somatostatin Receptor-4 Agonist SM-I-26 Mitigates Lipopolysaccharide-Induced Inflammatory Gene Expression in Microglia

Somatostatin receptor subtype 4 (SSTR4) is expressed in BV2 microglia, suggesting that SSTR4 agonists may impact microglia function. This study assessed the high-affinity SSTR4 agonist SM-I-26 (SMI) (0 nM, 10 nM, 1000 nM) against lipopolysaccharide (LPS)-induced inflammation (0, 10 or 100 ng/ml) over 6 or 24 h in BV2 microglia. Cell viability, nitrite output and mRNA expression changes of genes associated with our target (Sstr4), inflammation (Tnf-α, Il-6, Il-1β, inos), anti-inflammatory and anti-oxidant actions (Il-10, Catalase), and mediators of Aβ binding/phagocytosis (Msr1, Cd33, Trem1, Trem2) were measured. At 6 h SMI showed no effect across all conditions. At 24 h SMI (10 and 1000 nM) upregulated Sstr4 expression under inflammatory and non-inflammatory conditions. At 24 h SMI downregulated expression of the inflammatory cytokines Tnf-α (1000 nM within all LPS concentrations) and Il-6 (10 nM within 0 and 10 ng/ml LPS). At 24 h 10 nM SMI upregulated Il-10, while 1000 nM upregulated Catalase under inflammatory and non-inflammatory conditions. At 24 h Msr1 and Cd33 were upregulated by 1000 nM SMI under non-inflammatory conditions, while Trem1 was downregulated by 10 and 1000 nM SMI under mildly inflammatory and non-inflammatory conditions. These results show that SMI had concentration and time-dependent effects on mRNA expression of genes associated with different states of microglial activation. The SMI reduced Tnf-α and Il-6 inflammatory gene expression, and increased Il-10 anti-inflammatory gene expression, identifies anti-inflammatory actions of SSTR4 agonists extend to microglia.

Protective Role of Capsaicin in Neurological Disorders: An Overview

Different pathological conditions that begin with slow and progressive deformations, cause irreversible affliction by producing loss of neurons and synapses. Commonly it is referred to as 'protein misfolding' diseases or proteinopathies and comprises the latest definition of neurological disorders (ND). Protein misfolding dynamics, proteasomal dysfunction, aggregation, defective degradation, oxidative stress, free radical formation, mitochondrial dysfunctions, impaired bioenergetics, DNA damage, neuronal Golgi apparatus fragmentation, axonal transport disruption, Neurotrophins (NTFs) dysfunction, neuroinflammatory or neuroimmune processes, and neurohumoral changes are the several mechanisms that embark the pathogenesis of ND. Capsaicin (8-Methyl-N-vanillyl-6-nonenamide) one of the major phenolic components in chili peppers (Capsicum) distinctively triggers the unmyelinated C-fiber and acts on Transient Receptor Potential Vanilloid-1, which is a Ca²⁺ permeable, non-selective cation channel. Several studies have shown the neuroprotective role of capsaicin against oxidative damage, behavioral impairment, with 6-hydroxydopamine (6-OHDA) induced Parkinson's disease, pentylenetetrazol-induced seizures, global cerebral ischemia, and streptozotocin-induced Alzheimer's disease. Based on these lines of evidence, capsaicin can be considered as a potential constituent to develop suitable neuro-pharmacotherapeutics for the management and treatment of ND. Furthermore, exploring newer horizons and carrying out proper clinical trials would help to bring out the promising effects of capsaicin to be recommended as a neuroprotectant.

Perinatal exposure to synergistic multiple stressors lead to cellular and behavioral deficits mimicking Schizophrenia like pathology

Protein malnourishment and immune stress are potent perinatal stressors, encountered by children born under poor socioeconomic conditions. Thus, it is necessary to investigate how such stressors synergistically contribute towards developing neurological disorders in affected individuals. Pups from Wistar females, maintained on normal (high-protein, HP:20%) and low-protein (LP:8%) diets were used. Single and combined exposures of Poly I:C (viral mimetic: 5 mg/kg body weight) and Lipopolysaccharide (LPS; bacterial endotoxin: 0.3 mg/kg body weight) were injected to both HP and LP pups at postnatal days (PND) 3 and 9 respectively, creating eight groups: HP (control); HP+Poly I:C; HP+LPS; HP+Poly I:C+LPS; LP; LP+Poly I:C; LP+LPS; LP+Poly I:C+LPS (multi-hit). The effects of stressors on hippocampal cytoarchitecture and behavioral abilities were studied at PND 180. LP animals were found to be more vulnerable to immune stressors than HP animals and symptoms like neuronal damage, spine loss, downregulation of Egr 1 and Arc proteins, gliosis and behavioral deficits were maximum in the multi-hit group. Thus, from these findings it is outlined that cellular and behavioral changes that occur following multi-hit exposure may predispose individuals to developing Schizophrenia-like pathologies during adulthood.

Summary: This study reports that exposure to perinatal multi-hit stress (protein malnourishment and immune stress) causes changes in the hippocampal cells alongside behavioral deficits which are also observed in Schizophrenic condition.

PACAP and VIP Modulate LPS-Induced Microglial Activation and Trigger Distinct Phenotypic Changes in Murine BV2 Microglial Cells

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) are two structurally related immunosuppressive peptides. However, the underlying mechanisms through which these peptides regulate microglial activity are not fully understood. Using lipopolysaccharide (LPS) to induce an inflammatory challenge, we tested whether PACAP or VIP differentially affected microglial activation, morphology and cell migration. We found that both peptides attenuated LPS-induced expression of the microglial activation markers Iba1 and iNOS (### p < 0.001), as well as the pro-inflammatory mediators IL-1β, IL-6, Itgam and CD68 (### p < 0.001). In contrast, treatment with PACAP or VIP exerted distinct effects on microglial morphology and migration. PACAP reversed LPS-induced soma enlargement and increased the percentage of small-sized, rounded cells (54.09% vs. 12.05% in LPS-treated cells), whereas VIP promoted a phenotypic shift towards cell subpopulations with mid-sized, spindle-shaped somata (48.41% vs. 31.36% in LPS-treated cells). Additionally, PACAP was more efficient than VIP in restoring LPS-induced impairment of cell migration and the expression of urokinase plasminogen activator (uPA) in BV2 cells compared with VIP. These results suggest that whilst both PACAP and VIP exert similar immunosuppressive effects in activated BV2 microglia, each peptide triggers distinctive shifts towards phenotypes of differing morphologies and with differing migration capacities.

NNC 26-9100 increases Aβ1-42 phagocytosis, inhibits nitric oxide production and decreases calcium in BV2 microglia cells

Microglia are the resident immune cell of the brain involved in the development and progression of Alzheimer's disease (AD). Modulation of microglia activity represents a potential mechanism for treating AD. Herein, the compound NNC 26-9100 (NNC) was evaluated in toxicity, nitric oxide release, Aβ1-42 uptake and cytosolic calcium assays during lipopolysaccharide (LPS)-activated conditions using mouse BV2 microglia cells. After 24 hours, LPS increased cell toxicity in the alamar blue and lactate dehydrogenase assays, increased nitrite release, and increase cytoplasmic calcium. Addition of NNC decreased the LPS-induce lactate dehydrogenase release, had no effect in the alamar blue assay, decreased nitrite release and decreased cytosolic calcium. In the absence of LPS, NNC increased uptake of FITC-tagged Aβ1-42. These data demonstrate that NNC treatment decreases nitrosative stress and microglia cell damage during LPS-induced activation and enhances phagocytosis of Aβ1-42 during non-inflammatory conditions. Thus, NNC 26-9100 may have beneficial effects in AD and in inflammatory diseases of the brain through enhancement of microglial Aβ clearance, and cell protective effects through prevention of elevated cytosolic calcium and inhibition of nitric oxide release.

Octreotide inhibits secretion of IGF-1 from orbital fibroblasts in patients with thyroid-associated ophthalmopathy via inhibition of the NF-κB pathway

PURPOSE

We investigated the effect of octreotide, a long-acting somatostatin (SST) analogue, on IGF-1 secretion and its possible mechanism of action in orbital fibroblasts (OFs) from patients with thyroid-associated ophthalmopathy (TAO).

MATERIALS AND METHODS

OFs were isolated from the orbital fat of patients with TAO or healthy individuals. The expression level of insulin-like growth factor (IGF)-1, at the protein and mRNA level, was determined with ELISA and quantitative RT-PCR, respectively. The expression pattern of somatostatin receptor (SSTR) 2, which has the highest affinity for octreotide, was examined by flow cytometry. The activity of NF-κB pathway was determined by examining the levels of phosphorylation of IKKα/β and p65, and degradation of IκB via western blot analysis, and by measuring the activity of NF-kB-dependent luciferase via transfection with plasmids containing luciferase and NF-κB binding site.

RESULTS

OFs from patients with TAO showed significantly higher levels of IGF-1 secretion and NF-κB activity even in the absence of stimulation, compared to those from controls. Treatment with octreotide reduced the level of IGF-1 secretion in OFs from patients with TAO, but not in OFs from controls. OFs from patients with TAO expressed higher levels of SSTR2 on the cell surface, compared to controls. In addition, the expression of IGF-1 at the protein and mRNA level was dependent on the activity of NF-κB pathway in OFs from patients with TAO. Furthermore, treatment with octreotide reduced on the activity of NF-κB pathway in OFs from patients with TAO.

CONCLUSION

OFs from patients with TAO showed significantly higher levels of IGF-1 secretion via up-regulation of NF-κB activity. Treatment with octreotide inhibited the secretion of IGF-1 by reducing the NF-κB pathway in OFs, which expressed higher levels of SSRT2 on the cell surface, from patients with TAO.

Nuclear factor-kappa B (NF-κB) in pathophysiology of Parkinson disease: Diverse patterns and mechanisms contributing to neurodegeneration

Parkinson's disease (PD), the most common movement disorder, comprises several pathophysiologic mechanisms including misfolded alpha-synuclein aggregation, inflammation, mitochondrial dysfunction, and synaptic loss. Nuclear Factor-Kappa B (NF-κB), as a key regulator of a myriad of cellular reactions, is shown to be involved in such mechanisms associated with PD, and the changes in NF-κB expression is implicated in PD. Alpha-synuclein accumulation, the characteristic feature of PD pathology, is known to trigger NF-κB activation in neurons, thereby propagating apoptosis through several mechanisms. Furthermore, misfolded alpha-synuclein released from degenerated neurons, activates several signaling pathways in glial cells which culminate in activation of NF-κB and production of pro-inflammatory cytokines, thereby aggravating neurodegenerative processes. On the other hand, NF-κB activation, acting as a double-edged sword, can be necessary for survival of neurons. For instance, NF-κB activation is necessary for competent mitochondrial function and deficiency in c-Rel, one of the NF-κB proteins, is known to propagate DA neuron loss via several mechanisms. Despite the dual role of NF-κB in PD, several agents by selectively modifying the mechanisms and pathways associated with NF-κB, can be effective in attenuating DA neuron loss and PD, as reviewed in this paper.

Neuroprotective effect of the somatostatin receptor 5 agonist L-817,818 on retinal ganglion cells in experimental glaucoma

Somatostatin plays important roles in modulating neuronal functions by activating the five specific G-protein coupled receptors (sst1-sst5). Previous studies have demonstrated that sst5 were expressed in retinal ganglion cells (RGCs) and sst5 agonist attenuated the α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid-induced retinal neurotoxicity. In this study, we investigated effects and underlying mechanisms of the sst5 agonist L-817,818 on RGC injury induced by elevated intraocular pressure (COH) in experimental glaucoma. Our results showed that intraperitoneal administration of L-817,818 significantly reduced RGC loss and decreased the number of terminal deoxynucleotidyl transferase mediated dUTP nick-end labeling (TUNEL)-positive RGCs in COH retinas, suggesting that L-817,818 may attenuate RGC apoptosis. Consistently, in COH retinas with L-817,818 administration, both the down-regulated mRNA and protein levels of anti-apoptotic Bcl-2 and the up-regulated mRNA and protein levels of pro-apoptotic Bax were partially reversed. L-817,818 administration downregulated the expression of apoptosis-related proteins caspase-9 and caspase-3 in COH retinas. In addition, L-817,818 administration reduced the concentrations of reactive oxygen species/reactive nitrogen species and malondialdehyde, and ameliorated the functions of mitochondrial respiratory chain complex (MRCC). Our results imply that administration of the sst5 agonist L-817,818 reduces RGC loss in COH rats through decreasing RGC apoptosis, which is mediated by regulating Bcl-2/Bax balance, reducing oxidative stress and rescuing activities of MRCC. Activation of sst5 may provide neuroprotective roles for RGCs in glaucoma.

HOTAIR Accelerates Dyskinesia in a MPTP-Lesioned Mouse Model of PD via SSTR1 Methylation-Mediated ERK1/2 Axis

Homeobox transcript antisense RNA (HOTAIR), has been associated with neuroprotective effects in Parkinson's disease (PD). However, the underlying mechanisms still remain unclear. Hence, this present study attempted to clarify the functional relevance of HOTAIR in PD. We established an in vivo mouse model of PD using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and an in vitro cell model of PD by treating dopaminergic neuron MN9D cells with 1-methyl-4-phenylpyridinium species (MPP+). The expressions of somatostatin receptor 1 (SSTR1) and HOTAIR were altered to examine their effects on MN9D cell viability and apoptosis, as well as on movement impairments in MPTP-induced PD mouse model. The results indicated that HOTAIR expression was upregulated and SSTR1 was downregulated in in vivo and in vitro PD models. HOTAIR could bind to the promoter region of SSTR1, resulting in an increase of SSTR1 methylation through the recruitment of DNA methyltransferases in PD cell models. Notably, overexpression of HOTAIR and silencing of SSTR1 enhanced dopaminergic neuron apoptosis in MN9D cells and exacerbated dyskinesia in MPTP-induced PD mouse model. Collectively, overexpressed HOTAIR stimulates DNA methylation of SSTR1 to reduce SSTR1 expression, thereby accelerating dyskinesia and facilitating dopaminergic neuron apoptosis in a MPTP-lesioned PD mouse model via activation of the ERK1/2 axis.

The effects of hydro-ethanolic extract of Capparis spinosa (C. spinosa) on lipopolysaccharide (LPS)-induced inflammation and cognitive impairment: Evidence from in vivo and in vitro studies

ETHNOPHARMACOLOGICAL RELEVANCE

Capparis spinose (C. spinosa) belonging to Capparaeae, originates from dry areas in the west or central Asia and Mediterranean basin. For thousands of years, C. spinosa has been reported to be used as a therapeutic traditional medicine to relieve various ailments including rheumatism, pain and inflammatory diseases.

AIM OF THE STUDY

There are several studies mentioning that systemic inflammation results in learning and memory impairments through the activation of microglia. The objective of this study was to investigate the effect of C. spinosa on both in vivo and in vitro models of neuroinflammation and cognitive impairment using lipopolysaccharide (LPS).

MATERIALS AND METHODS

In vivo: 40 male rats were used in the present study. Cognitive impairment was induced using LPS (1 mg/kg/d; i.p.) for 4 weeks. Treatment with C. spinosa (100 and 300 mg/kg/d; p.o.) was performed 1 h before LPS administration. At the end of the experiment, rats were undergone for behavioral and biochemical analysis. In vitro: Primary microglia isolated from mouse was used in the present study. The cells were pretreated with C. spinosa extract (10-300 μg/ml) and then stimulated with LPS (1 μg/ml). The expression levels of inflammatory and anti-inflammatory cytokines were elucidated using Real-Time PCR and ELISA methods.

RESULTS

The escape latency in the Morris water maze test in the LPS group was significantly greater than the control group (p < 0.001), while, in extract-treated groups, it was less than the LPS group (p < 0.001). Additionally, we found that the levels of IL-1β, TNF-α, and iNOS/Arg-1 ratio was also significantly lower in extract-treated groups than the LPS group (p < 0.001). The results revealed that C. spinosa extract significantly reduced the levels of TNF-α, iNOS, COX-2, IL-1β, IL-6, NO and PGE2, and the ratios of iNOS/Arg-1 and NO/urea, following the LPS-induced inflammation in microglia (p < 0.001).

CONCLUSIONS

Our finding provides evidence that C. spinosa has a neuroprotective effect, and might be considered as an effective therapeutic agent for the treatment of neurodegenerative diseases that are accompanied by microglial activation, such as AD.

Subclinical Lipopolysaccharide from Salmonella Enteritidis Induces Dysregulation of Bioactive Substances from Selected Brain Sections and Glands of Neuroendocrine Axes

Bacterial lipopolysaccharide (LPS) can contribute to the pathogenesis and the clinical symptoms of many diseases such as cancer, mental disorders, neurodegenerative as well as metabolic diseases. The asymptomatic carrier state of Salmonella spp. is a very important public health problem. A subclinical single dose of LPS obtained from S. Enteritidis (5 μg/kg, i.v.) was administered to discern the consequences of changes of various brain peptides such as corticotropin-releasing hormone (CRH), gonadotropin-releasing hormone (GnRH), thyrotropin-releasing hormone (TRH), galanin (GAL), neuropeptide Y (NPY), somatostatin (SOM), substance P (SP), and vasoactive intestinal polypeptide (VIP) in selected clinically important brain sections and endocrine glands of the hypothalamic-pituitary-adrenal (HPA), -thyroid (HPT), -ovarian (HPO) axes. The study was conducted on ten immature crossbred female pigs. The brain peptides were extracted from the hypothalamus (medial basal hypothalamus, preoptic area, lateral hypothalamic area, mammillary bodies, and the stalk median eminence), and pituitary gland (adenohypophysis and neurohypophysis) sections and from the ovaries and adrenal and thyroid glands. There was no difference in health status between LPS and the control groups during the period of the experiment. Nevertheless, even a low single dose of LPS from S. Enteritidis that did not result in any clinical symptoms of disease induced dysregulation of various brain peptides, such as CRH, GnRH, TRH, GAL, NPY, SOM, SP, and VIP in selected brain sections of hypothalamus, pituitary gland and in the endocrine glands of the HPA, HPO, and HPT axes. In conclusion, the obtained results clearly show that subclinical LPS from S. Enteritidis can affect the brain chemistry structure and dysregulate bioactive substance from selected brain sections and glands of the neuroendocrine axes. The exact mechanisms by which LPS can influence major neuroendocrine axes are not fully understood and require further studies.

Reduced expression of somatostatin in GABAergic interneurons derived from induced pluripotent stem cells of patients with parkin mutations

Parkinson’s disease (PD) is associated with both motor and non-motor symptoms, including constipation, sensory neuropathy, depression, dementia and sleep disorder. Somatostatin (SST) is considered to be a modulator of GABAergic inhibitory transmission, and its levels are reduced in cerebrospinal fluid of PD patients. In the present study, we evaluated the changes in the expression of SST in GABAergic neurons derived from induced pluripotent stem cells (iPSCs) of PD patients. Neural cells were co-treated with the Wnt antagonist IWP-2 and Shh during neurosphere formation to induce GABA-positive forebrain interneurons. Quantitative analyses showed no significant differences, but slight decreases, in the potency of differentiation into GABAergic neurons derived from iPSCs between healthy control and patients with PARK2 mutations, who have been classified as a type of early-onset familial PD due to mutations in the parkin gene. Under this condition, the mRNA level of SST in GABAergic interneurons derived from iPSCs of PARK2-specific PD patients significantly decreased as neural maturation progressed. We also found that SST-positive GABAergic neurons were clearly reduced in GABAergic neurons derived from iPSCs of patients with PARK2 mutations. These findings suggest that the reduction in the expression level of SST in GABAergic interneurons of PD may, at least partly, lead to complex PD-induced symptoms.

The Role of Lipids in Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative disease characterized by a progressive loss of dopaminergic neurons from the nigrostriatal pathway, formation of Lewy bodies, and microgliosis. During the past decades multiple cellular pathways have been associated with PD pathology (i.e., oxidative stress, endosomal-lysosomal dysfunction, endoplasmic reticulum stress, and immune response), yet disease-modifying treatments are not available. We have recently used genetic data from familial and sporadic cases in an unbiased approach to build a molecular landscape for PD, revealing lipids as central players in this disease. Here we extensively review the current knowledge concerning the involvement of various subclasses of fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterols, and lipoproteins in PD pathogenesis. Our review corroborates a central role for most lipid classes, but the available information is fragmented, not always reproducible, and sometimes differs by sex, age or PD etiology of the patients. This hinders drawing firm conclusions about causal or associative effects of dietary lipids or defects in specific steps of lipid metabolism in PD. Future technological advances in lipidomics and additional systematic studies on lipid species from PD patient material may improve this situation and lead to a better appreciation of the significance of lipids for this devastating disease.

The Synergy of Aging and LPS Exposure in a Mouse Model of Parkinson's Disease

Aging is an inevitable physiological challenge occurring in organisms over time, and is also the most important risk factor of neurodegenerative diseases. In this study, we observed cellular and molecular changes of different age mice and LPS-induced Parkinson disease (PD) model. The results showed that behavioral performance and dopaminergic (DA) neurons were declined, accompanied by increased expression of pro-inflammatory factors (TLR2, p-NF-kB-p65, IL-1β and TNF-α), as well as pro-oxidative stress factor gp91phox in aged mice compared with young mice. Aging exaggerated inflammatory M1 microglia, and destroyed the balance between oxidation and anti-oxidation. The intranasal LPS instillation induced PD model in both young and aged mice. The poor behavioral performance and the loss of DA neurons as well as TLR2, p-NF-kB-p65, IL-1β, TNF-α, iNOS and gp91phox were further aggravated in LPS-aged mice. Interestingly, the expression of Nrf2 and HO-1 was up-regulated by LPS only in young LPS-PD mice, but not in aged mice. The results indicate that the synergy of aging process and LPS exposure may prominently aggravate the DA neurons loss caused by more serious neuroinflammation and oxidative stress in the brain.

Modulation of M1/M2 polarization by capsaicin contributes to the survival of dopaminergic neurons in the lipopolysaccharide-lesioned substantia nigra in vivo

The present study examined the neuroprotective effects of capsaicin (CAP) and explored their underlying mechanisms in a lipopolysaccharide (LPS)-lesioned inflammatory rat model of Parkinson’s dieases (PD). LPS was unilaterally injected into the substantia nigra (SN) in the absence or presence of CAP or capsazepine (CZP, a TRPV1 antagonist). The SN tissues were prepared for immunohistochemical staining, reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, western blot analysis, blood–brain barrier (BBB) permeability evaluation, and reactive oxygen species (ROS) detection. We found that CAP prevented the degeneration of nigral dopamine neurons in a dose-dependent manner and inhibited the expression of proinflammatory mediators in the LPS-lesioned SN. CAP shifted the proinflammatory M1 microglia/macrophage population to an anti-inflammatory M2 state as demonstrated by decreased expression of M1 markers (i.e., inducible nitric oxide synthase; iNOS and interleukin-6) and elevated expression of M2 markers (i.e., arginase 1 and CD206) in the SN. RT-PCR, western blotting, and immunohistochemical analysis demonstrated decreased iNOS expression and increased arginase 1 expression in the CAP-treated LPS-lesioned SN. Peroxynitrate production, reactive oxygen species levels and oxidative damage were reduced in the CAP-treated LPS-lesioned SN. The beneficial effects of CAP were blocked by CZP, indicating TRPV1 involvement. The present data indicate that CAP regulated the M1 and M2 activation states of microglia/macrophage in the LPS-lesioned SN, which resulted in the survival of dopamine neurons. It is therefore likely that TRPV1 activation by CAP has therapeutic potential for treating neurodegenerative diseases, that are associated with neuroinflammation and oxidative stress, such as PD.

A drug that activates a neuron-protecting protein in the brain may help treat Parkinson’s disease (PD). Scientists believe neurons die during PD because of an over-activation of proinflammatory markers within immune cell populations, such as the microglia and macrophage cells found in the central nervous system and the brain. Now, Byung Kwan Jin at Kyung Hee University in Seoul and Won-Ho Shin at the Korea Institute of Toxicology in Daejeon and co-workers have demonstrated that a proinflammatory state can be reversed in rat PD models by administering capsaicin, an analgesic drug. Capsaicin activates a receptor protein that is highly expressed in neurons, microglia and astrocytes, and may play a role in neuronal function and motor control. The protein activation reversed the inflammatory state of the immune cells, providing a more protective environment for neurons.

Kir6.1/K-ATP channel modulates microglia phenotypes: implication in Parkinson's disease

Classical activation (M1 phenotype) and alternative activation (M2 phenotype) are the two polars of microglial activation states that can produce either neurotoxic or neuroprotective effects in the immune pathogenesis of Parkinson’s disease (PD). Exploiting the beneficial properties of microglia cells by modulating their polarization states provides great potential for the treatment of PD. However, the mechanism that regulates microglia polarization remains elusive. Here we demonstrated that Kir6.1-containing ATP-sensitive potassium (Kir6.1/K-ATP) channel switched microglia from the detrimental M1 phenotype toward the beneficial M2 phenotype. Kir6.1 knockdown inhibited M2 polarization and simultaneously exaggerated M1 microglial inflammatory responses, while Kir6.1 overexpression promoted M2 polarization and synchronously alleviated the toxic phase of M1 microglia polarization. Furthermore, we observed that the Kir6.1 deficiency dramatically exacerbated dopaminergic neuron death companied by microglia activation in mouse model of PD. Mechanistically, Kir6.1 deficiency enhanced the activation of p38 MAPK–NF-κB pathway and increased the ratio of M1/M2 markers in the substantia nigra compacta of mouse model of PD. Suppression of p38 MAPK in vivo partially rescued the deleterious effects of Kir6.1 ablation on microglia phenotype and dopaminergic neuron death. Collectively, our findings reveal that Kir6.1/K-ATP channel modulates microglia phenotypes transition via inhibition of p38 MAPK–NF-κB signaling pathway and Kir6.1/K-ATP channel may be a promising therapeutic target for PD.

Neurochemical characterization of nerve fibers in the porcine gallbladder wall under physiological conditions and after the administration of Salmonella enteritidis lipopolysaccharides (LPS)

Lipopolysaccharides (LPS, bacterial endotoxin) are a component of the cellular membrane of Gram-negative bacteria, which is known as an important pathological factor. In spite of many previous studies describing multidirectional negative effects of LPS on living organisms, the knowledge concerning the influence of bacterial endotoxins on the gallbladder innervation is extremely scarce. The present study, based on the immunofluorescence technique, describes the changes in the neurochemical characterization of nerves within various parts of the porcine gallbladder (neck, body and fundus) after the administration of low doses of LPS. The obtained results show that even low doses of bacterial endotoxins affect the nerve structures within the gallbladder wall and the intensity of fluctuations in immunoreactivity to particular substances clearly depends on the part of the investigated organ. The most evident changes were observed in the case of fibers exhibiting the presence of neuropeptide Y (an increase from 7.84 ± 0.17 to 14.66 ± 0.37) in the neck, substance P (an increase from 0.88 ± 0.1 to 8.4 ± 0.3) in the body and the vesicular acetylocholine transporter in the gallbladder's fundus (an increase from 4.29 ± 0.18 to 11.01 ± 0.26). The mechanisms of the observed changes still remain unclear, but probably they are connected with the pro-inflammatory and/or neurodegenerative activity of LPS.

Modulation of the main porcine enteric neuropeptides by a single low-dose of lipopolysaccharide (LPS) Salmonella Enteritidis

Background

The present research was conducted to investigate the influence of a low, single dose of LPS, which does not result in any clinical symptoms of intoxication on the expression of selected neuropeptides within the intestines of the domestic pig.

Methods

This experiment was conducted on immature female pigs of the Pitrain × Duroc breed (n = five per group). Seven days after the intravenous injection of 10 mL saline solution for control animals and 5 μg/kg b.w. (in 10 mL saline solution) LPS Salmonella Enteritidis for the experimental group, the excised segments of duodenum, jejunum, ileum, ileocecal valve, caecum, descending colon, transverse colon, ascending colon and rectum were prepared to extract the main enteric neuropeptides, including GAL, NPY, SOM, SP, VIP.

Results

The results of this research indicate that single low-dose LPS S. Enteritidis produced changes in the content of the selected neuropeptides of the porcine intestine. The most visible changes were observed in the transverse colon, where LPS induced the increase of GAL expression from 19.41 ± 7.121 to 92.92 ± 11.447 ng/g tissue.

Conclusion

The exact functions of the substances studied and mechanisms of responses to LPS action depend on the sections of the intestines. The mechanisms of observed changes are not fully understood, but fluctuations in neuronal active substance levels may be connected with neurodegenerative and/or pro-inflammatory activity of LPS.

Peripheral immune tolerance alleviates the intracranial lipopolysaccharide injection-induced neuroinflammation and protects the dopaminergic neurons from neuroinflammation-related neurotoxicity

BACKGROUND

Neuroinflammation plays a critical role in the onset and development of neurodegeneration disorders such as Parkinson's disease. The immune activities of the central nervous system are profoundly affected by peripheral immune activities. Immune tolerance refers to the unresponsiveness of the immune system to continuous or repeated stimulation to avoid excessive inflammation and unnecessary by-stander injury in the face of continuous antigen threat. It has been proved that the immune tolerance could suppress the development of various peripheral inflammation-related diseases. However, the role of immune tolerance in neuroinflammation and neurodegenerative diseases was not clear.

METHODS

Rats were injected with repeated low-dose lipopolysaccharide (LPS, 0.3 mg/kg) intraperitoneally for 4 days to induce peripheral immune tolerance. Neuroinflammation was produced using intracranial LPS (15 μg) injection. Inflammation cytokines were measured using enzyme-linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qRT-PCR). Microglial activation were measured using immunostaining of Iba-1 and ED-1. Dopaminergic neuronal damage was evaluated using immunochemistry staining and stereological counting of TH-positive neurons. Behavioral impairment was evaluated using amphetamine-induced rotational behavioral assessment.

RESULTS

Compared with the non-immune tolerated animals, pre-treatment of peripheral immune tolerance significantly decreased the production of inflammatory cytokines, suppressed the microglial activation, and increased the number of dopaminergic neuronal survival in the substantia nigra.

CONCLUSIONS

Our results indicated that peripheral immune tolerance attenuated neuroinflammation and inhibited neuroinflammation-induced dopaminergic neuronal death.

Piperine Augments the Protective Effect of Curcumin Against Lipopolysaccharide-Induced Neurobehavioral and Neurochemical Deficits in Mice

The aim of the present study was to investigate the protective effects of curcumin alone and in combination with piperine against lipopolysaccharide (LPS)-induced neurobehavioral and neurochemical deficits in the mice hippocampus. Mice were treated with curcumin (100, 200, and 400 mg/kg, p.o.) and piperine (20 mg/kg, p.o.) for 7 days followed by LPS (0.83 mg/kg, i.p.) administration. Animals exhibited anxiety and depressive-like phenotype after 3 and 24 h of LPS exposure, respectively. LPS administration increased the oxido-nitrosative stress as evident by elevated levels of malondialdehyde, nitrite, and depletion of glutathione level in the hippocampus. Furthermore, we found raised level of pro-inflammatory cytokines (IL-1β and TNF-α) in the hippocampus of LPS-treated mice. Pretreatment with curcumin alleviated LPS-induced neurobehavioral and neurochemical deficits. Furthermore, co-administration of curcumin with piperine significantly potentiated the neuroprotective effect of curcumin. These results demonstrate that piperine enhanced the neuroprotective effect of curcumin against LPS-induced neurobehavioral and neurochemical deficits.

Neuropeptides and Microglial Activation in Inflammation, Pain, and Neurodegenerative Diseases

Microglial cells are responsible for immune surveillance within the CNS. They respond to noxious stimuli by releasing inflammatory mediators and mounting an effective inflammatory response. This is followed by release of anti-inflammatory mediators and resolution of the inflammatory response. Alterations to this delicate process may lead to tissue damage, neuroinflammation, and neurodegeneration. Chronic pain, such as inflammatory or neuropathic pain, is accompanied by neuroimmune activation, and the role of glial cells in the initiation and maintenance of chronic pain has been the subject of increasing research over the last two decades. Neuropeptides are small amino acidic molecules with the ability to regulate neuronal activity and thereby affect various functions such as thermoregulation, reproductive behavior, food and water intake, and circadian rhythms. Neuropeptides can also affect inflammatory responses and pain sensitivity by modulating the activity of glial cells. The last decade has witnessed growing interest in the study of microglial activation and its modulation by neuropeptides in the hope of developing new therapeutics for treating neurodegenerative diseases and chronic pain. This review summarizes the current literature on the way in which several neuropeptides modulate microglial activity and response to tissue damage and how this modulation may affect pain sensitivity.

Antidepressant-like effect of pramipexole in an inflammatory model of depression

Pramipexole (PPX), a dopamine D2/3 receptor preferring agonist, is currently in use for the treatment of Parkinson's disease symptoms and restless legs syndrome. Recently, anti-inflammatory properties of PPX have been shown in an autoimmune model of multiple sclerosis, and case reports indicate PPX ameliorates depressive symptoms. Since peripheral inflammation is known to induce depression-like behavior in rodents, we assessed the potential antidepressant effect of PPX in an inflammatory model of depression induced by LPS. Repeated (daily for 7days, 1mg/kg, i.p.), but not acute (1h before LPS) treatment with PPX abolished the depression-like behavior induced by LPS (0.1mg/kg, i.p.) in the forced swim test, and the anhedonic behavior in the splash test. Interestingly, PPX per se decreased interleukin 1β levels and reversed LPS-induced increase in its content in mice hippocampus⋅ Repeated PPX treatment also prevented the increase in hippocampal levels of the 3-nitrotyrosine protein adducts induced by LPS. Haloperidol (0.2mg/kg, i.p.) and sulpiride (50mg/kg, i.p.) were unable to prevent the antidepressant-like effect of PPX in LPS-treated mice. Altogether, these results suggest that the observed antidepressant-like effect of PPX in LPS-treated mice may be dependent on its anti-inflammatory properties and may not be related to dopamine D2 receptor activation.

Alkaloids from piper longum protect dopaminergic neurons against inflammation-mediated damage induced by intranigral injection of lipopolysaccharide

Background

Alkaloids from Piper longum (PLA), extracted from P. longum, have potent anti-inflammatory effects. The aim of this study was to investigate whether PLA could protect dopaminergic neurons against inflammation-mediated damage by inhibiting microglial activation using a lipopolysaccharide (LPS)-induced dopaminergic neuronal damage rat model.

Methods

The animal behaviors of rotational behavior, rotarod test and open-field test were investigated. The survival ratio of dopaminergic neurons and microglial activation were examined. The dopamine (DA) and its metabolite were detected by high performance liquid chromatography (HPLC). The effects of PLA on the expression of interleukin (IL)-6, interleukin (IL)-1β and tumor necrosis factor (TNF)-α were detected by enzyme-linked immunosorbent assay (ELISA). Reactive oxygen species (ROS) and nitric oxide (NO) were also estimated.

Results

We showed that the survival ratio of tyrosine hydroxylase-immunoreactive (TH-ir) neurons in the substantia nigra pars compacta (SNpc) and DA content in the striatum were reduced after a single intranigral dose of LPS (10 μg) treatment. The survival rate of TH-ir neurons in the SNpc and DA levels in the striatum were significantly improved after treatment with PLA for 6 weeks. The over-activated microglial cells were suppressed by PLA treatment. We also observed that the levels of inflammatory cytokines, including TNF-α, IL-6 and IL-1β were decreased and the excessive production of ROS and NO were abolished after PLA treatment. Therefore, the behavioral dysfunctions induced by LPS were improved after PLA treatment.

Conclusion

This study suggests that PLA plays a significant role in protecting dopaminergic neurons against inflammatory reaction induced damage.

Fasudil Enhances Therapeutic Efficacy of Neural Stem Cells in the Mouse Model of MPTP-Induced Parkinson's Disease

Bone marrow-derived neural stem cells (NSCs) are ideal cells for cellular therapy because of their therapeutic potential for repairing and regenerating damaged neurons. However, the optimization of implanted cells and the improvement of microenvironment in the central nervous system (CNS) are still two critical elements for enhancing therapeutic effect. In the current study, we observed the combined therapeutic effect of NSCs with fasudil in an 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease (PD) mouse model and explored the possible cellular and molecular mechanisms. The results clearly show that combined treatment of NSCs with fasudil further improves motor capacity of PD mice, thus exerting double effect in treating MPTP-PD. The combined intervention more effectively protected dopaminergic (DA) neurons from loss in the substantia nigra pars compacta (SNpc), which may be associated with the increased number and survival of transplanted NSCs in the brain. Compared with the treatment of fasudil or NSCs alone, the combined intervention more effectively inhibited the activation and aggregation of microglia and astrocytes, displayed stronger anti-inflammatory and antioxidant effects, induced more neurotrophic factor NT-3, and affected the dynamic homeostasis of NMDA and AMPA receptors in MPTP-PD mice. Our study demonstrates that intranasal administration of NSCs, followed by fasudil administration, is a promising cell-based therapy for neuronal lesions.

Clinical efficacy and safety of lansoprazole combined with somatostatin in treatment of acute upper gastrointestinal bleeding

AIM: To investigate the clinical effects of lansoprazole combined with somatostatin in the treatment of acute upper gastrointestinal bleeding.

METHODS: Eighty-six patients with acute upper gastrointestinal hemorrhage treated from January 2011 to December 2013 in Yuyao Second People's Hospital were randomly divided into a combination treatment group and a control group. The control group was given lansoprazole alone, and the combination group was given lansoprazole combined with somatostatin. The total response rate, time to successful hemostasis, treatment duration and adverse reactions were compared between the two groups.

RESULTS: The total response rate was significantly higher in the combination group than in the control group (93.0% vs 72.9%, P < 0.05). The time to successful hemostasis and treatment duration were significantly shorter in the combination group than in the control group (25.7 h ± 8.7 h vs 44.7 h ± 10.3 h, 6.7 d ± 1.1 d vs 11.8 d ± 1.7 d, P < 0.05). There was no adverse reaction in either group.

CONCLUSION: Lansoprazole combined with somatostatin in the treatment of acute upper gastrointestinal bleeding is associated with higher response rate, shorter bleeding time and treatment duration, and fewer adverse reactions compared with lansoprazole alone.

The G2019S LRRK2 mutation increases myeloid cell chemotactic responses and enhances LRRK2 binding to actin-regulatory proteins

The Leucine rich repeat kinase 2 (LRRK2) gene is genetically and biochemically linked to several diseases that involve innate immunity. LRRK2 protein is highly expressed in phagocytic cells of the innate immune system, most notably in myeloid cells capable of mounting potent pro-inflammatory responses. Knockdown of LRRK2 protein in these cells reduces pro-inflammatory responses. However, the effect of LRRK2 pathogenic mutations that cause Parkinson's disease on myeloid cell function is not clear but could provide insight into LRRK2-linked disease. Here, we find that rats expressing G2019S LRRK2 have exaggerated pro-inflammatory responses and subsequent neurodegeneration after lipopolysaccharide injections in the substantia nigra, with a marked increase in the recruitment of CD68 myeloid cells to the site of injection. While G2019S LRRK2 expression did not affect immunological homeostasis, myeloid cells expressing G2019S LRRK2 show enhanced chemotaxis both in vitro in two-chamber assays and in vivo in response to thioglycollate injections in the peritoneum. The G2019S mutation enhanced the association between LRRK2 and actin-regulatory proteins that control chemotaxis. The interaction between G2019S LRRK2 and actin-regulatory proteins can be blocked by LRRK2 kinase inhibitors, although we did not find evidence that LRRK2 phosphorylated these interacting proteins. These results suggest that the primary mechanism of G2019S LRRK2 with respect to myeloid cell function in disease may be related to exaggerated chemotactic responses.