TSPO Levels Research Articles

Transcriptional landscape of a hypoxia response identifies cell-specific pathways for adaptation.

How the HIF-1 (Hypoxia-Inducible) transcription factor drives and coordinates distinct responses to low oxygen across diverse cell types is poorly understood. We present a multi-tissue single-cell gene-expression atlas of the hypoxia response of the nematode Caenorhabditis elegans . This atlas highlights how cell-type-specific HIF-1 responses overlap and diverge among and within neuronal, intestinal, and muscle tissues. Using the atlas to guide functional analyses of candidate muscle-specific HIF-1 effectors, we discovered that HIF-1 activation drives downregulation of the tspo-1 ( TSPO, Translocator Protein) gene in vulval muscle cells to modulate a hypoxia-driven change in locomotion caused by contraction of body-wall muscle cells. We further showed that in human cardiomyocytes HIF-1 activation decreases levels of TSPO and thereby alters intracellular cholesterol transport and the mitochondrial network. We suggest that TSPO-1 is an evolutionarily conserved mediator of HIF-1-dependent modulation of muscle and conclude that our gene-expression atlas can help reveal how HIF-1 drives cell-specific adaptations to hypoxia.

МИТОХОНДРИАЛЬНЫЙ БЕЛОК-ТРАНСЛОКАЗА 18 кДа КАК БИОМАРКЕР РАДИАЦИОННО-ИНДУЦИРОВАННОГО НЕЙРОВОСПАЛЕНИЯ

The review presents current knowledge about the structure of the18 kDa translocator protein TSPO, its polymorphic variants, regulation of its gene expression and function in the cells of CNS. Particular attention is paid to its role in mitochondrial homeostasis in microglia under neuroinflammation in the long-term period after ionizing radiation exposure. Data on the effectiveness of several TSPO ligands for diagnostic imaging and treatment of neuroinflammation for restoring cognitive functions in neurodegenerative pathologies are summarized. Based on the TSPO level in the brain and in the peripheral blood cells late after irradiation, TSPO is discussed as a potential marker of neuroinflammation development.

Age‐ and Sex‐ dependent changes in Translocator Protein 18 kDa (TSPO) expression, cellular sources, and association with amyloid‐β plaques in the 5XFAD murine model of Alzheimer’s Disease

AbstractBackgroundAlzheimer’s disease (AD) is a neurodegenerative disorder that affects cognition, memory, and social abilities with devastating effects on individuals and families. The hallmark AD pathology is the formation of amyloid‐β‐(Aβ)‐plaques and Tau neurofibrillary tangles leading to neurodegeneration. Neuroinflammation, and microglia activation, also play an important role in the initiation and progression of AD, a process that begins earlier than cognitive decline. TSPO is a well‐validated and widely used biomarker of neuroinflammation that is expressed in glial cells, and it is markedly increased in the brain of AD subjects and in AD animal models. Previous studies have not assessed a detailed trajectory of TSPO in the progression of AD. In the present study, we determined the age‐and sex‐dependent increase in brain TSPO levels, cellular sources, and association with Aβ‐plaques in parallel with behavior.MethodBehavioral performance was measured using the Barnes Maze (cognition) in male and female wild‐type (WT) and 5XFAD mice at 3 months (3M), and 7 months (7M). To evaluate pathological endpoints, we measured Aβ‐load (number, size, and % area covered), TSPO quantitative autoradiography using the TSPO‐specific radioligand [3H]‐DPA‐713, and quadruple‐label immunofluorescent confocal imaging to determine the cellular sources of the TSPO response and its association with Aβ‐plaques.ResultAt 3M, we observed no significant differences in behavioral performance between WT and 5XFAD in either sex. At 7M, 5XFAD males showed no cognitive dysfunction, however, there was a significant cognitive impairment in 5XFAD females. We found an increase of Aβ‐plaques in an age‐and sex‐dependent manner. TSPO autoradiography showed a significant increase in TSPO levels in 5XFAD mice in both sexes and ages with a higher increase in females. Furthermore, we show that TSPO expression is colocalized with plaque‐associated microglia and not astrocytes.ConclusionThese results indicate that brain TSPO is an early biomarker of neuroinflammation and TSPO levels increase at the same time that Aβ‐aggregation and much earlier than cognitive decline. Furthermore, the increase in TSPO levels was associated with microglia surrounding or embedded with Aβ‐plaques suggesting a role in plaque formation.

Interaction between peripheral and central immune markers in clinical high risk for psychosis

Neuroinflammatory events prior to the diagnosis of schizophrenia may play a role in transition to illness. To date only one in-vivo study has investigated this association between peripheral proinflammatory cytokines and brain markers of inflammation (e.g., mitochondrial 18 kDa translocator protein, TSPO) in schizophrenia, but none in its putative prodrome.In this study, we primarily aimed to (1) test study group (clinical high-risk (CHR) and healthy controls) differences in peripheral inflammatory markers and test for any associations with symptom measures, (2) investigate the interaction between brain TSPO levels (dorsolateral prefrontal cortex (DLPFC) and hippocampus) and peripheral inflammatory clusters (entire cohort and (CHR) group independently) within a relatively large group of individuals at CHR for psychosis (N = 38) and healthy controls (N = 20). Participants underwent structural brain magnetic resonance imaging (MRI) and TSPO [18F]FEPPA positron emission tomography (PET) scans. Serum samples were assessed for peripheral inflammatory markers (i.e., CRP and interleukins). For exploratory analysis, we aimed to examine cluster differences for symptom measures and identify independent peripheral predictors of brain TSPO expression.Here, we report increased IL-8 levels that are positively correlated with prodromal general symptom severity and showed trend-level association with apathy in CHR. We identified distinct inflammatory clusters characterized by inflammatory markers (IL-1 β, IL-2, IFN-γ) that were comparable between entire cohort and CHR. TSPO levels did not differ between inflammatory clusters (entire cohort or CHR). Finally, we show that CRP, IL-1 β, TNF-α, and IFN-γ levels were the independent peripheral predictors of brain TSPO expression.Thus, alterations in brain TSPO expression in response to inflammatory processes are not evident in CHR. Taken together, clustering by inflammatory status is a promising strategy to characterize the interaction between brain TSPO and peripheral markers of inflammation.

The role of proteins implicated in skin steroidogenesis in acne vulgaris development

Background. Acne vulgaris belongs to androgen-dependent diseases where androgens cause sebaceous gland hypertrophy with a subsequent enlargement of sebum production.
 Aims. Determination of the expression profile of steroidogenesis-related proteins in normal skin and skin of patients with acne.
 Material and methods. Immunohistochemical assay was carried out to characterize TSPO, StAR, CYP11A1, and 3-hydroxysteroid dehydrogenase expression in skin of patients with acne vulgaris and in normal skin.
 Results. Expression levels of a protein TSPO which is involved in a steroidogenesis-limited step was increased in mature sebocytes of acne vulgaris patients. StAR, CYP11A1, and 3-hydroxysteroid dehydrogenase immunovisualization was found both in normal skin and in the skin of acne patients.
 Conclusions. The revealed alterations in expression of steroidogenesis-related protein in acne skin may indicate not only the conversion of steroids produced by external steroidogenesis organs but elevated steroids local production as well. The fact may account both for sebaceous gland hyperplasia and inflammation sustenance in skin.

A single dose of ketamine cannot prevent protracted stress-induced anhedonia and neuroinflammation in rats

Worldwide, millions of people suffer from treatment-resistant depression. Ketamine, a glutamatergic receptor antagonist, can have a rapid antidepressant effect even in treatment-resistant patients. A proposed mechanism for the antidepressant effect of ketamine is the reduction of neuroinflammation. To further explore this hypothesis, we investigated whether a single dose of ketamine can modulate protracted neuroinflammation in a repeated social defeat (RSD) stress rat model, which resembles features of depression. To this end, male animals exposed to RSD were injected with ketamine (20 mg/kg) or vehicle. A combination of behavioral analyses and PET scans of the inflammatory marker TSPO in the brain were performed. Rats submitted to RSD showed anhedonia-like behavior in the sucrose preference test, decreased weight gain, and increased TSPO levels in the insular and entorhinal cortices, as observed by [11C]-PK11195 PET. Whole brain TSPO levels correlated with corticosterone levels in several brain regions of RSD exposed animals, but not in controls. Ketamine injection 1 day after RSD disrupted the correlation between TSPO levels and serum corticosterone levels, but had no effect on depressive-like symptoms, weight gain or the protracted RSD-induced increase in TSPO expression in male rats. These results suggest that ketamine does not exert its effect on the hypothalamic–pituitary–adrenal axis by modulation of neuroinflammation.

Neuroinflammation and flortaucipir PET in non‐fluent/agrammatic variant of primary progressive aphasia and/or apraxia of speech

AbstractBackgroundNeuroinflammation, a hallmark of frontotemporal dementia, has been sparsely studied in vivo. However, neuroinflammation is a potentially important therapeutic target and biomarkers of inflammation would be welcome. To determine the anatomical specificity of a putative biomarker for inflammation, translocator protein 18 kDa (TSPO) imaging, we used 11C‐PBR28 PET to measure TSPO levels in patients with the non‐fluent/agrammatic variant of primary progressive aphasia (nfvPPA) and/or apraxia of speech (AOS).MethodsSixteen patients with nfvPPP/AOS underwent PET using 11C‐PBR28 and 18F‐flortaucipir. All patients were PET amyloid‐negative except two, with a non‐AD flortaucipir PET. Thirty healthy controls underwent PET imaging using 11C‐PBR28 (13 controls) or 18F‐flortaucipir (17 controls). Patients (9/16 women, mean age 65±5.9 years) did not differ significantly in age from the controls (17/30 women, mean age 66±9.3 years). V T values for 11C‐PBR28 were calculated with the Logan plot and a metabolite‐corrected arterial input function. For 18F‐flortaucipir, the SUV ratio over the cerebellar gray matter was calculated for t = 80‐100 min. All images were corrected for partial volume effect. A full factorial analysis was performed on V T and SUVR values between patients and controls at the voxel‐wise level.ResultsCompared to controls, patients showed increased V T and SUVR values (p < 0.001 uncorrected) in left inferior, middle and superior frontal gyri, as well as in the left putamen and pallidum. However, peak uptake of 18F‐flortaucipir was localized in Broca’s area, epicenter of the pathology, while the distribution of 11C‐PBR28 V T was more extensive in the frontal lobe, including precentral gyrus, and other regions outside of the frontal lobe, as the supramarginal gyrus and superior temporal sulcus, as well as a small area in the posterior extent of the right inferior frontal gyrus.Conclusions 11C‐PBR28 and 18F‐flortaucipir uptake patterns corresponded to anatomical areas known to be related to the specific language functions that are impaired in nfvPPA and apraxia of speech. Thus, 11C‐PBR28 seems to be a suitable radioligand for detecting neuroinflammation in nfvPPA. Furthermore, the more extensive anatomical distribution of abnormal 11C‐PBR28 uptake, as compared to 18F‐flortaucipir uptake, suggests that inflammation is key to the progression of the pathologic process in nfvPPA.

Absence of the mitochondrial translocator protein 18kDa in mice does not affect body weight or food intake responses to altered energy availability.

Changes in mitochondrial function in a variety of cells/tissues are critical for orchestrating systemic energy homeostasis and are linked to the development of obesity and many of its comorbidities. The mitochondrial translocator protein of 18kDa (TSPO) is expressed in organs throughout the body, including the brain, liver, adipose tissue, gonads and adrenal glands, where it is implicated in regulating steroidogenesis and cellular metabolism. Prior work from our group and others has shown that, in rodents, TSPO levels are altered in adipose tissue by obesity and that modulation of TSPO activity may impact systemic glucose homeostasis. Furthermore, in vitro studies in a variety of cell types have implicated TSPO in mediating cellular energetics and substrate utilisation. Although mice with germline global TSPO deficiency (TSPO-/- ) have no reported changes in body weight under standard husbandry conditions, we hypothesised that, given the roles of TSPO in regulating mitochondrial function and cellular metabolic flexibility, these animals may have alterations in their systemic response to altered energy availability, either nutritional excess or insufficiency. In agreement with published work, compared to wild-type (TSPO+/+ ) littermates, TSPO-/- mice of both sexes did not exhibit differences in body weight on standard chow. Furthermore, following a 12-hour overnight fast, there was no difference in weight loss or compensatory food intake during re-feeding. Five weeks of feeding a high-fat diet (HFD) did not reveal any impact of the absence of TSPO on body weight gain in either male or female mice. Basal blood glucose levels and glucose clearance in a glucose tolerance test were influenced by feeding a HFD diet but not by genotype. In conclusion, in the paradigms examined, germline global deletion of TSPO did not change the physiological response to deviations in systemic energy availability at the whole organism level.

TSPO levels in multiple sclerosis lesions reflect microglial density rather than activation state.

TSPO levels in multiple sclerosis lesions reflect microglial density rather than activation state.

Dissection of neuroinflammation in schizophrenia

AimsSchizophrenia is notoriously becoming one of the world's most debilitating mental disorders, affecting 1 in 100 people. There is increasing evidence that neuroinflammation plays a part in the pathogenesis of schizophrenia and other psychotic disorders; microglial activity acting as a marker for neuroinflammatory reactions in the brain. Furthermore, cannabis is an illicit substance that also evokes a similar response in the neuroimmune activity. This project explores how cannabis exposure influences an elevation in neuroinflammatory responses through TSPO levels, and whether this information can help us determine if cannabis use and increased TSPO levels can be associated with a risk factor for developing psychosis.Method55 participants (36 males and 19 females) were recruited from the community by the IRIS (Inflammatory Reaction in Schizophrenia) team at the IoPPN, King's College London, from which 34 patients with a diagnosis of schizophrenia and 21 healthy controls took part in the study. The eligible participants underwent clinical assessments and PET scanning, from which cannabis use history and PET data were collected. Participant neuroinflammatory levels are represented by [18F]DPA-714 volume and different regions of grey matter in the brain were analysed through multivariate analyses, the confounding variables being age and TSPO genotype.ResultA statistically significant association is shown between participants who have had exposure to cannabis and participants who have not had any exposure in their lifetime. The differences across the prioritised brain regions of interest were robust, the association appearing more apparent and statistically significant in the total (p = .00) and temporal grey matter (p = .00) regions of the brain. This may suggest that cannabis exposure influences the [18F]DPA-714 VT in the significant regions of interest. However, a negative association is seen with current use, the quantity of use, and the frequency of use.ConclusionThe initial findings for cannabis exposure show us a positive association with increased TSPO levels, however, limitations must be taken into account. Although we cannot readily establish that elevated TSPO levels in cannabis users can presently act as a risk factor marker for developing psychosis from this particular study, we can utilise this data to continue our research in disclosing a new system to predict the occurrence of psychosis.

TSPO Expression Modulatory Effect of Acetylcholinesterase Inhibitor in the Ischemic Stroke Rat Model.

We performed in vivo PET imaging with 3-[18F]F-CP118,954 (1) for acetylcholinesterase (AChE) and [18F]fluoromethyl-PBR28-d2 (2) for translocator protein 18-kDa (TSPO) to investigate the inflammatory brain response after stroke. Imaging studies were performed in the middle cerebral artery occlusion (MCAO) Sprague-Dawley rat model for a period of three weeks. The percentage injected dose per tissue weight (%ID/g) of striatum of 1, and cortex of 2 were obtained, respectively. To trace the sequential inflammatory responses, AChE imaging of 1 was done on post-MCAO day 2, after giving cold PK-11195 for 1 day, and TSPO imaging of 2 was carried out on post-MCAO day 11, after giving donepezil for 10 days. AChE activity in the MCAO-lesioned side were significantly higher than that of the contralateral side on day one, and TSPO activity was highest on day 11. TSPO inhibitor, PK-11195 did not affect AChE activity on day two, while AChE inhibitor, donepezil significantly lowered TSPO binding on day 12. Our study demonstrates that AChE level is elevated in the early course of brain ischemia as a trigger for the inflammatory response, and TSPO level is elevated persistently throughout the post-ischemic injury in the brain. Also, the AChE inhibitor may be able to inhibit or delay neurotoxic inflammatory responses and serve as a beneficial treatment option.

TSPO PET upregulation predicts epileptic phenotype at disease onset independently from chronic TSPO expression in a rat model of temporal lobe epilepsy

Neuroinflammation is a key component of epileptogenesis, the process leading to acquired epilepsy. In recent years, with the development of non-invasive in vivo positron emission tomography (PET) imaging of translocator protein 18 kDa (TSPO), a marker of neuroinflammation, it has become possible to perform longitudinal studies to characterize neuroinflammation at different disease stages in animal models of epileptogenesis. This study aimed to utilize the prognostic capability of TSPO PET imaging at disease onset (2 weeks post-SE) to categorize epileptic rats with distinct seizure burden based on TSPO levels at disease onset and investigate their association to TSPO expression at the chronic epilepsy stage. Controls (n = 14) and kainic acid-induced status epilepticus (KASE) rats (n = 41) were scanned non-invasively with [18F]PBR111 PET imaging measuring TSPO expression. Animals were monitored using video-electroencephalography (vEEG) up to chronic disease (12 weeks post-SE), at which TSPO levels ([3H]PK11195) as well as other post-mortem abnormalities (namely synaptic density ([3H]UCB-J), neuronal loss (NeuN), and neurodegeneration (FjC)) were investigated. By applying multivariate analysis, TSPO PET imaging at disease onset identified three KASE groups with significantly different spontaneous recurrent seizures (SRS) burden (defined as rare SRS, sporadic SRS, and frequent SRS) (p = 0.003). Interestingly, TSPO levels were significantly different when comparing the three KASE groups (p < 0.0001), with the frequent SRS group characterized only by a limited focal TSPO increase at disease onset. On the contrary, TSPO measured during chronic epilepsy was found to be the highest in the frequent SRS group and correlated with seizure burden (r = 0.826, p < 0.0001). Importantly, early and chronic TSPO levels did not correlate (r = −0.05). Finally, significant pathological changes in neuronal loss, synaptic density, and neurodegeneration were found not only when compared to control animals (p < 0.01), but also between the three KASE rat categories in the hippocampus (p < 0.05). Early and chronic TSPO upregulation following epileptogenic insult appear to be driven by two superimposed dynamic processes. The former is associated with epileptogenesis as measured at disease onset, while the latter is related to seizure frequency as quantified during chronic epilepsy.

Surface translocator protein 18kDa (TSPO) localization on immune cells upon stimulation with LPS and in ART-treated HIV+ subjects.

Translocator protein 18kDa (TSPO) is a well-known outer mitochondrial membrane protein and it is widely used as a biomarker of neuroinflammation and brain injury. Although it is thought that TSPO plays key roles in a multitude of host cell functions, including steroid biosynthesis, apoptosis, generation of reactive oxygen species, and proliferation, some of these functions have recently been questioned. Here, we report the unexpected finding that circulating immune cells differentially express basal levels of TSPO on their cell surface, with a high percentage of monocytes and neutrophils expressing cell surface TSPO. In vitro stimulation of monocytes with LPS significantly increases the frequency of cells with surface TSPO expression in the absence of altered gene expression. Importantly, the LPS increase in TSPO cell surface expression in monocytes appears to be selective for LPS because two other distinct monocyte activators failed to increase the frequency of cells with surface TSPO. Finally, when we quantified immune cell TSPO surface expression in antiretroviral therapy-treated HIV+ donors, a chronic inflammatory disease, we found significant increases in the frequency of TSPO surface localization, which could be pharmacologically suppressed with ∆9 -tetrahydrocannabinol. These findings suggest that cell surface TSPO in circulating leukocytes could serve as a peripheral blood-based biomarker of inflammation.

A Novel Interaction of Translocator Protein 18\xa0kDa (TSPO) with NADPH Oxidase in Microglia

In the brain neuropil, translocator protein 18 kDa (TSPO) is a stress response protein that is upregulated in microglia and astrocytes in diverse central nervous system pathologies. TSPO is widely used as a biomarker of neuroinflammation in preclinical and clinical neuroimaging studies. However, there is a paucity of knowledge on the function(s) of TSPO in glial cells. In this study, we explored a putative interaction between TSPO and NADPH oxidase 2 (NOX2) in microglia. We found that TSPO associates with gp91phox and p22phox, the principal subunits of NOX2 in primary murine microglia. The association of TSPO with gp91phox and p22phox was observed using co-immunoprecipitation, confocal immunofluorescence imaging, and proximity ligation assay. We found that besides gp91phox and p22phox, voltage-dependent anion channel (VDAC) also co-immunoprecipitated with TSPO consistent with previous reports. When we compared lipopolysaccharide (LPS) stimulated microglia to vehicle control, we found that a lower amount of gp91phox and p22phox protein co-immunoprecipitated with TSPO suggesting a disruption of the TSPO-NOX2 subunits association. TSPO immuno-gold electron microscopy confirmed that TSPO is present in the outer mitochondrial membrane but it is also found in the endoplasmic reticulum (ER), mitochondria-associated ER membrane (MAM), and in the plasma membrane. TSPO localization at the MAM may represent a subcellular site where TSPO interacts with gp91phox and p22phox since the MAM is a point of communication between outer mitochondria membrane proteins (TSPO) and ER proteins (gp91phox and p22phox) where they mature and form the cytochrome b558 (Cytb558) heterodimer. We also found that an acute burst of reactive oxygen species (ROS) increased TSPO levels on the surface of microglia and this effect was abrogated by a ROS scavenger. These results suggest that ROS production may alter the subcellular distribution of TSPO. Collectively, our findings suggest that in microglia, TSPO is associated with the major NOX2 subunits gp91phox and p22phox. We hypothesize that this interaction may regulate Cytb558 formation and modulate NOX2 levels, ROS production, and redox homeostasis in microglia.

Visualization of translocator protein (18kDa) (TSPO) in the retina of diabetic retinopathy rats using fluorine-18-DPA-714.

To investigate the feasibility of a noninvasive method for imaging translocator protein (18kDa) (TSPO) in the retina of diabetic retinopathy (DR) rats using fluorine-18-DPA-714 ([18F]-DPA-714) micro-positron emission tomography (PET)/X-ray computed tomography (CT). Sprague-Dawley (SD) rats were intraperitoneally injected with streptozocin (STZ) (65mgkg-1, ip) to induce diabetes mellitus (DM). The TSPO in both eyes was detected by PET/CT using [18F]-DPA-714 12weeks after the establishment of the DM model. The mean standardized uptake value (SUVmean) was analyzed. Western blot and quantitative real-time polymerase chain reaction (PCR) were performed to detect the TSPO protein and mRNA levels in the retina. PET/CT results showed that the SUV of [18F]-DPA-714 was markedly reduced in the retina of DR rats compared with that of normal controls 12weeks after diabetes induction. The SUVmean of regions of interest (ROIs) in the retinas of DR and normal control rats was 0.883 ± 0.078 and 2.525 ± 0.213 (P < 0.001), respectively. The results of PET/CT were in line with the Western blots and quantitative real-time PCR. The PET results demonstrated that TSPO was decreased in the early stage of DR. [18F]-DPA-714 PET/CT appears to be a useful noninvasive imaging method for detecting TSPO in the retina. A decrease in the TSPO level in the retina may play an important role in the development of DR.

Anxiolytic and Anti-depressive Like Effects of Translocator Protein (18kDa) Ligand YL-IPA08 in a Rat Model of Postpartum Depression.

Translocator protein 18kDa (TSPO) is mainly distributed in the outer mitochondrial membrane of steroid-synthesizing cells in the central and peripheral nervous systems. It mediates cholesterol transportation across the phospholipid membrane, which is a prerequisite for neurosteroid synthesis. Though the ligand of TSPO has clinical value in the diagnosis and treatment of neuropsychiatric disorders, the pharmacological study of TSPO for anti-postpartum depression has not been reported. In this study, the classical method of reproductive hormone withdrawal was used to construct a rat model of postpartum depression (PPD). The effect of YL-IPA08, a new ligand compound of TSPO, on PPD was evaluated using multiple behavioral tests at progressive time points. Additionally, real-time quantitative PCR, Western-blotting and an enzyme linked immunosorbent assay were conducted to elucidate the potential molecular mechanism of such effect. We report that the levels of TSPO and neurosteroids in the hippocampus and prefrontal cortex were significantly decreased in PPD rats compared to healthy controls. After 3weeks of drug treatment, the levels of TSPO and neurosteroids in the hippocampus of PPD rats were increased, and anxiety and depressive like behaviors were alleviated. Meanwhile, compared with sertraline treatment, a positive control in this study, YL-IPA08 treatment had a shorter onset time. Our results suggest that the anxiolytic and anti-depressive activity of YL-IPA08 has significant value in the treatment of PPD and that TSPO may be a potential new target for the treatment of PPD.

Peripheral cytokine and fatty acid associations with neuroinflammation in AD and aMCI patients: An exploratory study

Neuroinflammation is thought to be important in the progression of Alzheimer’s disease (AD). To evaluate cerebral inflammation radioligands that target TSPO, a translocator protein strongly expressed in microglia and macrophages during inflammation, can be used in conjunction with positron emission tomography (PET) imaging. In AD patients, neuroinflammation is up-regulated compared to both healthy volunteers as well as to subjects with amnestic Mild Cognitive Impairment. Peripheral biomarkers, such as serum cytokines and total fatty acids (FAs), can also be indicative of the inflammatory state of subjects with neurodegenerative disorders. To understand whether peripheral biomarkers are predictive of neuroinflammation we conducted a secondary exploratory analysis of two TSPO imaging studies conducted in subjects with AD, aMCI and aged matched healthy volunteers. We examined the association between candidate peripheral biomarkers (including amyloid beta, cytokines and serum total fatty acids) with brain TSPO levels. Our results showed that serum IL-6 and IL-10 are higher in AD compared to the aMCI and healthy volunteers while levels of some fatty acids are modulated during the disease. A limited number of associations were observed between region-specific inflammation and fatty acids in aMCI patients, and between amyloid beta 42 and brain inflammation in AD, however no associations were present with systemic cytokines. Our study suggests that while TSPO binding and systemic IL-6 and IL-10 were elevated in AD, serum amyloid beta, cytokines and fatty acids were generally not predictive of the disease nor correlated with neuroinflammation.

Investigation of a Novel Salt Stress-Responsive Pathway Mediated by Arabidopsis DEAD-Box RNA Helicase Gene AtRH17 Using RNA-Seq Analysis.

Previously, we reported that overexpression of AtRH17, an Arabidopsis DEAD-box RNA helicase gene, confers salt stress-tolerance via a pathway other than the well-known salt stress-responsive pathways. To decipher the salt stress-responsive pathway in AtRH17-overexpressing transgenic plants (OXs), we performed RNA-Sequencing and identified 397 differentially expressed genes between wild type (WT) and AtRH17 OXs. Among them, 286 genes were upregulated and 111 genes were downregulated in AtRH17 OXs relative to WT. Gene ontology annotation enrichment and KEGG pathway analysis showed that the 397 upregulated and downregulated genes are involved in various biological functions including secretion, signaling, detoxification, metabolic pathways, catabolic pathways, and biosynthesis of secondary metabolites as well as in stress responses. Genevestigator analysis of the upregulated genes showed that nine genes, namely, LEA4-5, GSTF6, DIN2/BGLU30, TSPO, GSTF7, LEA18, HAI1, ABR, and LTI30, were upregulated in Arabidopsis under salt, osmotic, and drought stress conditions. In particular, the expression levels of LEA4-5, TSPO, and ABR were higher in AtRH17 OXs than in WT under salt stress condition. Taken together, our results suggest that a high AtRH17 expression confers salt stress-tolerance through a novel salt stress-responsive pathway involving nine genes, other than the well-known ABA-dependent and ABA-independent pathways.

Sex differences in the brain expression of steroidogenic molecules under basal conditions and after gonadectomy.

The brain is a steroidogenic tissue. It expresses key molecules involved in the synthesis and metabolism of neuroactive steroids, such as steroidogenic acute regulatory protein (StAR), translocator protein 18kDa (TSPO), cytochrome P450 cholesterol side-chain cleavage enzyme (P450scc), 3β-hydroxysteroid dehydrogenases (3β-HSD), 5α-reductases (5α-R) and 3α-hydroxysteroid oxidoreductases (3α-HSOR). Previous studies have shown that the levels of brain steroids are different in male and female rats under basal conditions and after gonadectomy. In the present study, we assessed gene expression of key neurosteroidogenic molecules in the cerebral cortex and cerebellum of gonadally intact and gonadectomised adult male and female rats. In the cerebellum, the basal mRNA levels of StAR and 3α-HSOR were significantly higher in females than in males. By contrast, the mRNA levels of TSPO and 5α-R were significantly higher in males. In the cerebral cortex, all neurosteroidogenic molecules analysed showed similar mRNA levels in males and females. Gonadectomy increased the expression of 5α-R in the brain of both sexes, although it affected the brain expression of StAR, TSPO, P450scc and 3α-HSOR in females only and with regional differences. Although protein levels were not investigated in the present study, our findings indicate that mRNA expression of steroidogenic molecules in the adult rat brain is sexually dimorphic and presents regional specificity, both under basal conditions and after gonadectomy. Thus, local steroidogenesis may contribute to the reported sex and regional differences in the levels of brain neuroactive steroids and may be involved in the generation of sex differences in the adult brain function.

Differential effects of TSPO ligands on mitochondrial function in mouse microglia cells

The translocator protein 18 kDa (TSPO), initially characterized as peripheral benzodiazepine receptor, is a conserved outer mitochondrial membrane protein, implicated in cholesterol transport thereby affecting steroid hormone biosynthesis, as well as in general mitochondrial function related to bioenergetics, oxidative stress, and Ca2+ homeostasis. TSPO is highly expressed in steroidogenic tissues such as adrenal glands, but shows low expression in the central nervous system. During various disease states such as inflammation, neurodegeneration or cancer, the expression of mitochondrial TSPO in affected tissues is upregulated. The expression of TSPO can be traced for diagnostic purpose by high affinity radio-ligands. Moreover, the function of TSPO is modulated by synthetic as well as endogenous ligands with agonistic or antagonistic properties. Thus, TSPO ligands serve functions as both important biomarkers and putative therapeutic agents.In the present study, we aimed to characterize the effects of TSPO ligands on mouse BV-2 microglia cells, which express significant levels of TSPO, and analyzed the effect of XBD173, PK11195, and Ro5-4864, as well as the inflammatory reagent Lipopolysaccharides (LPS) on neurosteroid synthesis and on basic mitochondrial functions such as oxidative phosphorylation, mitochondrial membrane potential and Ca2+ homeostasis. Specific TSPO-dependent effects were separated from off-target effects by comparing lentiviral TSPO knockdown with shRNA scramble-controls and wild-type BV-2 cells. Our data demonstrate ligand-specific effects on different cellular functions in a TSPO-dependent or independent manner, providing evidence for both specific TSPO-mediated, as well as off-target effects.