Yin and Yang of PDGF-mediated signaling pathway in the context of HIV infection and drug abuse

Decrease of miR-19b-3p in Brain Microvascular Endothelial Cells Attenuates Meningitic Escherichia coli-Induced Neuroinflammation via TNFAIP3-Mediated NF-κB Inhibition

Meningitic Escherichia coli can traverse the host’s blood–brain barrier (BBB) and induce severe neuroinflammatory damage to the central nervous system (CNS). During this process, the host needs to reasonably balance the battle between bacteria and brain microvascular endothelial cells (BMECs) to minimize inflammatory damage, but this quenching of neuroinflammatory responses at the BBB is unclear. MicroRNAs (miRNAs) are widely recognized as key negative regulators in many pathophysiological processes, including inflammatory responses. Our previous transcriptome sequencing revealed numbers of differential miRNAs in BMECs upon meningitic E. coli infection; we next sought to explore whether and how these miRNAs worked to modulate neuroinflammatory responses at meningitic E. coli entry of the BBB. Here, we demonstrated in vivo and in vitro that meningitic E. coli infection of BMECs significantly downregulated miR-19b-3p, which led to attenuated production of proinflammatory cytokines and chemokines via increasing the expression of TNFAIP3, a negative regulator of NF-κB signaling. Moreover, in vivo injection of miR-19b-3p mimics during meningitic E. coli challenge further aggravated the inflammatory damage to mice brains. These in vivo and in vitro findings indicate a novel quenching mechanism of the host by attenuating miR-19b-3p/TNFAIP3/NF-κB signaling in BMECs in response to meningitic E. coli, thus preventing CNS from further neuroinflammatory damage.

Meningitic Escherichia coli-induced upregulation of PDGF-B and ICAM-1 aggravates blood-brain barrier disruption and neuroinflammatory response

Background

Blood-brain barrier (BBB) disruption and neuroinflammation are considered key mechanisms of pathogenic Escherichia coli invasion of the brain. However, the specific molecules involved in meningitic E. coli-induced BBB breakdown and neuroinflammatory response remain unclear. Our previous RNA-sequencing data from human brain microvascular endothelial cells (hBMECs) revealed two important host factors: platelet-derived growth factor-B (PDGF-B) and intercellular adhesion molecule-1 (ICAM-1), which were significantly upregulated in hBMECs after meningitic E. coli infection. Whether and how PDGF-B and ICAM-1 contribute to the development of E. coli meningitis are still unclear.

Methods

The western blot, real-time PCR, enzyme-linked immunosorbent assay, immunohistochemistry, and immunofluorescence were applied to verify the significant induction of PDGF-B and ICAM-1 by meningitic E. coli in vivo and in vitro. Evan’s blue assay and electric cell-substrate impedance sensing assay were combined to identify the effects of PDGF-B on BBB permeability. The CRISPR/Cas9 technology, cell-cell adhesion assay, and electrochemiluminescence assay were used to investigate the role of ICAM-1 in neuroinflammation subversion.

Results

We verified the significant induction of PDGF-B and ICAM-1 by meningitic E. coli in mouse as well as monolayer hBMECs models. Functionally, we showed that the increase of PDGF-B may directly enhance the BBB permeability by decreasing the expression of tight junction proteins, and the upregulation of ICAM-1 contributed to neutrophils or monocytes recruitment as well as neuroinflammation subversion in response to meningitic E. coli infection.

Conclusions

Our findings demonstrated the roles of PDGF-B and ICAM-1 in mediating bacterial-induced BBB damage as well as neuroinflammation, providing new concepts and potential targets for future prevention and treatment of bacterial meningitis.

Cerebrospinal fluid biomarkers and HIV-associated neurocognitive disorders in HIV-infected individuals in Rakai, Uganda

In the USA, increased cerebrospinal fluid (CSF) inflammatory cytokines have been observed in antiretroviral therapy (ART)-naive, HIV-seropositive individuals with HIV-associated neurocognitive disorder (HAND). We characterized the relationship between HAND and CSF biomarker expression in ART-naive, HIV-seropositive individuals in Rakai, Uganda. We analyzed CSF of 78 HIV-seropositive, ART-naive Ugandan adults for 17 cytokines and 20 neurodegenerative biomarkers via Luminex multiplex assay. These adults underwent neurocognitive assessment to determine their degree of HAND. We compared biomarker concentrations between high and low CD4 groups and across HAND classifications, adjusting for multiple comparisons. Individuals with CD4 <200 cells/μL (N = 38) had elevated levels of CSF Interleukin (IL)-2, IL-12, granulocyte-macrophage colony-stimulating factor (GM-CSF), TNF-α, matrix metalloproteinase (MMP)-1, MMP-7, and S100 calcium-binding protein B (S100B) and lower levels of amyloid β42. Individuals with CD4 351-500 cells/μL (N = 40) had significantly higher CSF levels of interleukin (IL)-1β, amyloid β42, and soluble receptor for advanced glycation end products (sRAGE). Increasing levels of S100B, platelet-derived growth factor-AA (PDGF-AA), brain-derived neurotrophic factor (BDNF), and sRAGE were associated with decreased odds of mild neurocognitive disorder (n = 22) or HIV-associated dementia (n = 15) compared with normal function (n = 30) or asymptomatic neurocognitive impairment (n = 11). Increased levels of interferon (IFN)-γ were associated with increased odds of mild neurocognitive impairment or HIV-associated dementia relative to normal or asymptomatic neurocognitive impairment. Proinflammatory CSF cytokines, chemokines, and neurodegenerative biomarkers were present in increasing concentrations with advanced immunosuppression and may play a role in the development of HAND. The presence of select CNS biomarkers may also play a protective role in the development of HAND.

Dysfunction of brain pericytes in chronic neuroinflammation

Brain pericytes are uniquely positioned within the neurovascular unit to provide support to blood brain barrier (BBB) maintenance. Neurologic conditions, such as HIV-1-associated neurocognitive disorder, are associated with BBB compromise due to chronic inflammation. Little is known about pericyte dysfunction during HIV-1 infection. We found decreased expression of pericyte markers in human brains from HIV-1-infected patients (even those on antiretroviral therapy). Using primary human brain pericytes, we assessed expression of pericyte markers (α1-integrin, α-smooth muscle actin, platelet-derived growth factor-B receptor β, CX-43) and found their downregulation after treatment with tumor necrosis factor-α (TNFα) or interleukin-1 β (IL-1β). Pericyte exposure to virus or cytokines resulted in decreased secretion of factors promoting BBB formation (angiopoietin-1, transforming growth factor-β1) and mRNA for basement membrane components. TNFα and IL-1β enhanced expression of adhesion molecules in pericytes paralleling increased monocyte adhesion to pericytes. Monocyte migration across BBB models composed of human brain endothelial cells and pericytes demonstrated a diminished rate in baseline migration compared to constructs composed only of brain endothelial cells. However, exposure to the relevant chemokine, CCL2, enhanced the magnitude of monocyte migration when compared to BBB models composed of brain endothelial cells only. These data suggest an important role of pericytes in BBB regulation in neuroinflammation.

First Japanese family with primary familial brain calcification due to a mutation in the PDGFB gene: an exome analysis study

AIMS

Primary familial brain calcification (PFBC) is a rare disorder characterized by abnormal deposits of calcium in the basal ganglia and cerebellum. PFBC can present with a spectrum of neuropsychiatric symptoms resembling those seen in dementia and schizophrenia. Mutations in a few genes have been identified as causing PFBC: namely, the SLC20A2 gene that codes for the sodium-dependent phosphate transporter and the PDGFRB gene that codes for the platelet-derived growth factor receptor β (PDGF-Rβ). A recent study identified mutations in PDGFB coding for PDGF-B, the main ligand for PDGF-Rβ, in six families with PFBC. Here we report the first Japanese family with PFBC carrying a mutation in PDGFB, which causes the substitution of an arginine with a stop codon at amino acid 149 of the PDGF-B protein (p. Arg149*).

METHODS

Clinical histories and computed tomography scan images were provided. Sanger sequencing was performed for the exome analysis of SLC20A2 and PDGFB genes.

RESULTS

One family member began to complain of auditory hallucination at 16 years of age and had been treated for schizophrenia. His father suffered from memory and gait disturbances in his late 60s. A computed tomography scan revealed a symmetrical area of calcification over the basal ganglia in both cases. A known mutation in PDGFB (c.445C>T, p.Arg149*) was consistently detected in both PFBC cases by Sanger sequencing. No mutations in SLC20A2 were detected.

CONCLUSIONS

Our findings suggest that this mutation in PDGF-B is responsible for PFBC in this Japanese family and that abnormal PDGF signaling may be involved in the pathophysiology of certain psychiatric disorders.

Growth factor signaling: implications for disease & therapeutics

Cells possess complex growth factor networks that play vital roles in regulating fundamental life processes. Such protein factors exert their action by binding to cognate cell specific receptors resulting in regulation of cell division, differentiation, chemotaxis or apoptosis. Engagement of receptors by their respective ligands results in activation of sequential protein phosphorylation cascades, culminating downstream into activation of gene transcription. These factors are expressed ubiquitously under a variety of conditions by normal as well as transformed cells, thereby underpinning their function in autocrine and paracrine stimulation of cells under several physiological and pathological conditions. Despite major advances in our understanding of growth factors, their paradoxical roles in normal cellular homeostasis and pathologies underpin the need to examine their roles in disease and health. The goal of this special issue is to present emerging trends in the roles that growth factors play in inflammatory disease processes that include cardiovascular, cancer, stroke and neurodegenerative processes associated with aging, viral infection and substance abuse with the ultimate aim to pave the way for future therapeutic breakthroughs.