Insulin-like growth factor binding protein-1-6 expression in activated microglia

The peripheral Atf3 + neuronal population is responsible for nerve regeneration at the early stage of nerve injury revealed by single-cell RNA sequencing

Peripheral nerve injury (PNI) can transform primary somatosensory neurons to a regenerative state. However, the details of the transcriptomic changes associated with the nerve regeneration of somatosensory neurons remain unclear. In this study, single-cell RNA sequencing (scRNA-seq) is conducted on mouse dorsal root ganglion (DRG) cells after the early stage of nerve injury on day 3 after chronic constriction injury (CCI). We observe that a novel CCI-induced neuronal population (CIP) emerge and express high levels of activating transcription factor ( Atf3), a neuronal injury marker. CIP neurons highly express regeneration-associated genes (RAGs) and are enriched in regeneration-related gene ontology (GO) terms, suggesting that these neurons can constitute a pro-regenerative population. Moreover, intercellular communication networks show that CIP neurons closely communicate with satellite glial cells (SGCs) and specifically transmit strong Fgf3- Fgfr1 signaling to SGCs, which could initiate regeneration-associated transcriptional changes in SGCs. We also confirm that regenerative progress occurs at the early stage of nerve injury because immunohistochemistry shows that the expression of ATF3 is significantly increased beginning at 3 days post-CCI and decreased at 1 month post-CCI. Our bioinformatics analysis at single-cell resolution advances the knowledge of regenerative dynamic transcriptional changes in DRG cells after injury and the underlying molecular mechanisms involved.

Lactate modulates microglia polarization via IGFBP6 expression and remodels tumor microenvironment in glioblastoma

Lactic acidosis has been reported in solid tumor microenvironment (TME) including glioblastoma (GBM). In TME, several signaling molecules, growth factors and metabolites have been identified to induce resistance to chemotherapy and to sustain immune escape. In the early phases of the disease, microglia infiltrates TME, contributing to tumorigenesis rather than counteracting its growth. Insulin-like Growth Factor Binding Protein 6 (IGFBP6) is expressed during tumor development, and it is involved in migration, immune-escape and inflammation, thus providing an attractive target for GBM therapy. Here, we aimed at investigating the crosstalk between lactate metabolism and IGFBP6 in TME and GBM progression. Our results show that microglia exposed to lactate or IGFBP6 significantly increased the Monocarboxylate transporter 1 (MCT1) expression together with genes involved in mitochondrial metabolism. We, also, observed an increase in the M2 markers and a reduction of inducible nitric oxide synthase (iNOS) levels, suggesting a role of lactate/IGFBP6 metabolism in immune-escape activation. GBM cells exposed to lactate also showed increased levels of IGFBP6 and vice-versa. Such a phenomenon was coupled with a IGFBP6-mediated sonic hedgehog (SHH) ignaling increase. We, finally, tested our hypothesis in a GBM zebrafish animal model, where we observed an increase in microglia cells and igfbp6 gene expression after lactate exposure. Our results were confirmed by the analysis of human transcriptomes datasets and immunohistochemical assay from human GBM biopsies, suggesting the existence of a lactate/IGFBP6 crosstalk in microglial cells, so that IGFBP6 expression is regulated by lactate production in GBM cells and in turn modulates microglia polarization.

Effects of adipokine administration to the hypothalamic preoptic area on body temperature in rats

The effects of adipokine administration to the hypothalamic preoptic area (POA), which is one of the body temperature (BT) regulation centers in the central nervous system, on BT were investigated in male Wistar rats. BT was measured in conscious rats using telemetry. Insulin-like growth factor-1 (IGF-1), interleukin-1β (IL-1β), monocyte chemoattractant protein-1 and lipocalin-2 produced hyperthermia, and the effects induced by IL-1β (25 ng) and IGF-1 (5 μg) were sustainable and remarkable. IL-6 did not show any significant effect. The IGF-1-induced effect was inhibited by pretreatment with IGF binding protein 3 (IGFBP3) or NVP-AEW541 (NVP, a selective inhibitor of type 1 IGF receptor tyrosine kinase, IGF1R TK). NVP-induced inhibition was observed only in the early phase of IGF-1-induced hyperthermia. In addition, IGF-1 increased the IL-1β concentration in the microdialysate of POA perfusion, but did not increase the IL-1β concentration in the plasma or the PGE₂ concentration in the microdialysate. These findings suggested that IGF-1 produced hyperthermia, which was mediated, at least a part, through an increased IL-1β concentration after activation of IGF1R TK in the POA, and the IGF-IGFBP system possibly participates in BT homeostasis in the POA.

The Role of Insulin-Like Growth Factors and Insulin-Like Growth Factor-Binding Proteins in the Nervous System

The insulin-like growth factors (IGF-I and IGF-II) and their receptors are widely expressed in nervous tissue from early embryonic life. They also cross the blood brain barriers by active transport, and their regulation as endocrine factors therefore differs from other tissues. In brain, IGFs have paracrine and autocrine actions that are modulated by IGF-binding proteins and interact with other growth factor signalling pathways. The IGF system has roles in nervous system development and maintenance. There is substantial evidence for a specific role for this system in some neurodegenerative diseases, and neuroprotective actions make this system an attractive target for new therapeutic approaches. In developing new therapies, interaction with IGF-binding proteins and other growth factor signalling pathways should be considered. This evidence is reviewed, gaps in knowledge are highlighted, and recommendations are made for future research.

Traditional Mongolian medicine Eerdun Wurile improves stroke recovery through regulation of gene expression in rat brain

ETHNOPHARMACOLOGICAL RELEVANCE

Eerdun Wurile (EW) is one of the key Mongolian medicines for treatment of neurological and cardiological disorders. EW is ranked most regularly used Mongolian medicine in clinic. Components of EW which mainly originate from natural products are well defined and are unique to Mongolian medicine.

AIM OF THE STUDY

Although the recipe of EW contains known neuroactive chemicals originated from plants, its mechanism of action has never been elucidated at molecular level. The objective of the present study is to explore the mechanism of neuroregenerative activity of EW by focusing on the regulation of gene expression in the brain of rat model of stroke.

MATERIALS AND METHODS

Rat middle cerebral artery occlusion (MCAO) models were treated with EW for 15 days. Then, total RNAs from the cerebral cortex of rat MCAO models treated with either EW or control (saline) were extracted and analyzed by transcriptome sequencing. Differentially expressed genes were analyzed for their functions during the recovery of ischemic stroke. The expression level of significantly differentially expressed genes such as growth factors, microglia markers and secretive enzymes in the lesion was further validated by RT-qPCR and immunohistochemistry.

RESULTS

Previously identified neuroactive compounds, such as geniposide (Yu et al., 2009), myristicin (Shin et al., 1988), costunolide (Okugawa et al., 1996), toosendanin (Shi and Chen, 1999) were detected in EW formulation. Bederson scale indicated that the treatment of rat MCAO models with EW showed significantly lowered neurological deficits (p < 0.01). The regional cerebral blood circulation was also remarkably higher in rat MCAO models treated with EW compared to the control group. A total of 186 genes were upregulated in the lesion of rat MCAO models treated with EW compared to control group. Among them, growth factors such as Igf1 (p < 0.05), Igf2 (p < 0.01), Grn (p < 0.01) were significantly upregulated in brain after treatment of rat MCAO models with EW. Meanwhile, greatly enhanced expression of microglia markers, as well as complementary components and secretive proteases were also detected.

CONCLUSION

Our data collectively indicated that EW enhances expression of growth factors including Igf1 and Igf2 in neurons and microglia, and may stimulate microglia polarization in the brain. The consequences of such activity include stimulation of neuron growth, hydrolysis and clearance of cell debris at the lesion, as well as the angiogenesis.

Insulin-Like Growth Factor (IGF)-I Modulates Endothelial Blood-Brain Barrier Function in Ischemic Middle-Aged Female Rats

In comparison with young females, middle-aged female rats sustain greater cerebral infarction and worse functional recovery after stroke. These poorer stroke outcomes in middle-aged females are associated with an age-related reduction in IGF-I levels. Poststroke IGF-I treatment decreases infarct volume in older females and lowers the expression of cytokines in the ischemic hemisphere. IGF-I also reduces transfer of Evans blue dye to the brain, suggesting that this peptide may also promote blood-brain barrier function. To test the hypothesis that IGF-I may act at the blood-brain barrier in ischemic stroke, 2 approaches were used. In the first approach, middle-aged female rats were subjected to middle cerebral artery occlusion and treated with IGF-I after reperfusion. Mononuclear cells from the ischemic hemisphere were stained for CD4 or triple-labeled for CD4/CD25/FoxP3 and subjected to flow analyses. Both cohorts of cells were significantly reduced in IGF-I-treated animals compared with those in vehicle controls. Reduced trafficking of immune cells to the ischemic site suggests that blood-brain barrier integrity is better maintained in IGF-I-treated animals. The second approach directly tested the effect of IGF-I on barrier function of aging endothelial cells. Accordingly, brain microvascular endothelial cells from middle-aged female rats were cultured ex vivo and subjected to ischemic conditions (oxygen-glucose deprivation). IGF-I treatment significantly reduced the transfer of fluorescently labeled BSA across the endothelial monolayer as well as cellular internalization of fluorescein isothiocyanate-BSA compared with those in vehicle-treated cultures, Collectively, these data support the hypothesis that IGF-I improves blood-brain barrier function in middle-aged females.

Stroke neuroprotection: oestrogen and insulin-like growth factor-1 interactions and the role of microglia

Oestrogen has been shown to be neuroprotective for stroke and other neural injury models. Oestrogen promotes a neuroprotective phenotype through myriad actions, including stimulating neurogenesis, promoting neuronal differentiation and survival, suppressing neuroinflammation and maintaining the integrity of the blood-brain barrier. At the molecular level, oestrogen directly modulates genes that are beneficial for repair and regeneration via the canonical oestrogen receptor. Increasingly, evidence indicates that oestrogen acts in concert with growth factors to initiate neuroprotection. Oestrogen and insulin-like growth factor (IGF)-1 act cooperatively to influence cell survival, and combined steroid hormone/growth factor interaction has been well documented in the context of neurones and astrocytes. Here, we summarise the evidence that oestrogen-mediated neuroprotection is critically dependent on IGF-1 signalling, and specifically focus on microglia as the source of IGF-1 and the locus of oestrogen-IGF-1 interactions in stroke neuroprotection.

The role of insulin-like growth factor 1 and its receptor in the formation and development of colorectal carcinoma

OBJECTIVE

To investigate the role of insulin-like growth factor (IGF)-1 and its receptor (IGF1R) in the formation and development of colorectal carcinoma.

METHODS

Colorectal tissue and matching serum samples were collected from patients with adenomatous polyps or carcinoma and healthy control subjects. IGF1R mRNA levels were determined via quantitative real-time reverse transcription-polymerase chain reaction. Serum IGF1 was quantified using enzyme-linked immunosorbent assay.

RESULTS

Serum IGF1 concentrations and mucosal IGF1R mRNA levels were significantly higher in patients with adenomatous polyps (n = 24) or carcinoma (n = 13) compared with healthy control subjects (n = 13). There was a significant positive correlation between serum IGF1 and mucosal IGF1R mRNA in patients with adenomatous polyps.

CONCLUSIONS

High circulating IGF1 concentrations and mucosal IGF1R expression may play important roles in both the formation and development of colorectal carcinoma. IGF1 and its receptor may be activated before carcinogenesis, and may promote the growth and malignant transformation of adenomatous polyps. IGF1 and IGF1R may be useful biomarkers for evaluating the stage and risk of carcinogenesis.

Selective regulation of growth factor expression in cultured cortical astrocytes by neuro-pathological toxins

Astrocytes are integrated in the complex regulation of neurodegeneration and neuronal damage in the CNS. It is well-known that astroglia produces a plethora of growth factors which might be protective for neurons. Growth factors prevent neurons from cell death and promote proliferation and differentiation of precursor cells. Previous data suggest that astrocytes may respond to toxic stimuli by a selective mobilization of guarding molecules. In the present study, we have investigated the potency of different pathological stimuli such as lipopolysaccharides, tumor necrosis factor alpha, glutamate, and hydrogen peroxide to activate cultured cortical astroglia and stimulate growth factor expression. Astroglial cultures were exposed to the above factors for 24h at non-toxic concentrations for astrocytes. Growth factor expression was analyzed by real-time PCR, oligo-microarray technique, and ELISA. Insulin-like growth factor-1 was selectively down-regulated by lipopolysaccharides and tumor necrosis factor alpha, bone morphogenetic protein 6 by all stimuli. In contrast, lipopolysaccharides, tumor necrosis factor alpha, and glutamate increased leukemia inhibitory factor. Fibroblast growth factor 2 was up-regulated by lipopolysaccharides and tumor necrosis factor alpha and down-regulated by hydrogen peroxide. Besides hydrogen peroxide, all other stimuli promoted vascular epithelial growth factor A mRNA and protein expression. It appears that lipopolysaccharides but not tumor necrosis factor alpha effects on vascular epithelial growth factor A depend on the classic NFkappaB pathway. Our data clearly demonstrate that astroglia actively responses to diverse pathological compounds by a selective expression pattern of growth factors. These findings make astrocytes likely candidates to participate in disease-specific characteristics of neuronal support or damage.

The role of connexins in controlling cell growth and gene expression

The purpose of this paper is to provide a brief overview of current thinking on the role of connexins, in particular Cx43, in growth regulation, and a more detailed discussion as to potential mechanisms involved with an emphasis on gene expression. While the precise molecular mechanism by which connexins can affect the growth of normal or tumor cells remains elusive, a number of exciting reports have expanded our understanding and are presented in some detail. Thus, we will discuss (Section 2): the role of protein-protein interactions in integrating connexins into multiple signal transduction pathways; phosphorylation at specific sites and reversal of growth inhibition; the role of the carboxy-terminal regulatory domain as a signaling molecule. Some of our latest work on the potential functions of endogenously produced carboxy-terminal fragments of Cx43 are also presented (Section 3). Finally, Section 4 will pay tribute to the rapidly emerging realization that connexins such as Cx43 and Cx32 exert important and extensive effects on gene expression, particularly those genes linked to growth regulation.

Gene expression changes after seizure preconditioning in the three major hippocampal cell layers

Rodents experience hippocampal damage after status epilepticus (SE) mainly in pyramidal cells while sparing the dentate granule cell layer (DGCL). Hippocampal damage was prevented in rats that had been preconditioned by brief seizures on 2 consecutive days before SE. To identify neuroprotective genes and biochemical pathways changed after preconditioning we compared the effect of preconditioning on gene expression in the CA1 and CA3 pyramidal and DGCLs, harvested by laser capture microscopy. In the DGCL the expression of 632 genes was altered, compared to only 151 and 58 genes in CA1 and CA3 pyramidal cell layers. Most of the differentially expressed genes regulate tissue structure and intra- and extracellular signaling, including neurotransmission. A selective upregulation of energy metabolism transcripts occurred in CA1 pyramidal cells relative to the DGCL. These results reveal a broad transcriptional response of the DGCL to preconditioning, and suggest several mechanisms underlying the neuroprotective effect of preconditioning seizures.

Einfluss von Ischämie/Hypoxie auf die HIF-1-Aktivität und Expression von hypoxieabhängigen Genen in der Kochlea der neugeborenen Ratte

BACKGROUND

Transcription factor HIF-1 (hypoxia-inducible factor-1) regulates the expression of genes which are involved in glucose supply, growth, metabolism, redox reactions and blood supply. Hypoxia and ischemia play an important role in the pathogenesis of tinnitus and hearing loss. Therefore, HIF-1 activity and the expression of HIF-1 dependent genes in the cochlea were examined under ischemic and hypoxic conditions.

MATERIAL AND METHODS

For the HIF-1 analysis, single-cell cultures of the organ of Corti (OC), stria vascularis (SV) and modiolus (MOD) were used. mRNA expression was analyzed in the organotypic culture using a microarray technique (RN U34-chip, Affymetrix).

RESULTS

Ischemia (hypoxia without glucose) and pure hypoxia increase the HIF-1 activity identically, with the highest increase found in MOD and OC. The HIF-1 alpha mRNA levels were found to be higher in SV than in the OC and MOD. During culturing, there is a clear increase in HIF-1 alpha mRNA and the expression of a number of HIF-1 dependent genes, such as Gapdh/glyceraldehyde-3-phosphate dehydrogenase, Slc2a1/solute carrier family 2 (facilitated glucose transporter), member 1, Tf/transferrin and Tfrc/transferrin receptor, in all three regions. In SV, MOD and OC, increase in the expression of Hmox1/hemoxygenase 1, Nos2/nitric oxide synthase, inducible and Tfrc is particularly high. Hypoxia (5 h) results in an increased expression of Igf2/Insulin-like growth factor 2.

CONCLUSION

The present data underline the contribution of radical forming processes to the pathogenesis of inner ear diseases. For experimental research, it is important to note that organotypic culture may be coupled with hypoxia.

Insulin-like growth factor I and II expression and modulation in amoeboid microglial cells by lipopolysaccharide and retinoic acid

Insulin-like growth factors I and II are known to regulate the development of the CNS. We examined the developmental changes in insulin-like growth factor I and insulin-like growth factor II expression in the postnatal rat corpus callosum. Insulin-like growth factor I and insulin-like growth factor II mRNA expression increased at 3 days as compared with 1 day whereas the protein expression increased up to 7 days. Insulin-like growth factor I and insulin-like growth factor II immunoexpression was specifically localized in round cells confirmed by double immunofluorescence with OX-42 to be the amoeboid microglial cells. Insulin-like growth factor I expression was observed up to 7 days in amoeboid microglial cells while insulin-like growth factor II expression was detected in 1-3 day old rats. Exposure of primary rat microglial cell cultures to lipopolysaccharide increased insulin-like growth factor I and insulin-like growth factor II mRNA and protein expression significantly along with their immunoexpression in microglial cells. The lipopolysaccharide-induced increase in insulin-like growth factor I and insulin-like growth factor II mRNA and protein expression was significantly decreased with all-trans-retinoic acid. We conclude that insulin-like growth factor I and insulin-like growth factor II expression in amoeboid microglial cells in the developing brain is related to their activation. Once the activation is inhibited, either by transformation of the amoeboid microglial cells into ramified microglia regarded as resting cells or as shown by the effect of all-trans-retinoic acid administration, insulin-like growth factor I and insulin-like growth factor II mRNA and protein expression is downregulated.

Microarrays and expression profiling in microglia research and in inflammatory brain disorders

Expression profiling by using microarrays is a powerful tool for investigating transcriptional changes in a variety of diseases. In this survey, microarray data selected from the literature from in vivo and in vitro studies are scrutinized to find differentially expressed genes in common within specific inflammatory conditions in brain or microglial cell cultures, if there are at least two independent investigations available. Viral encephalitis, multiple sclerosis, epileptic seizures, ischemic lesions, and traumatic brain injury are the disorders covered. Moreover, by taking into account expression data obtained from cultured microglia, two examples are presented of how one can deal (or should not deal) with lists of candidate genes showing up in these kinds of studies without sophisticated software programs. Finally, some general remarks are made about pivotal issues when beginning to use microarray technology.