Degradation of Extracellular Matrix by Matrix Metalloproteinase 2 Is Essential for the Establishment of the Blood-Brain Barrier in Drosophila

Ectopic expression of matrix metalloproteinases and filopodia extension via JNK activation are involved in the invasion of blood tumor cells in Drosophila mxc mutant

Drosophila mxcmbn1 mutant exhibits severe hyperplasia in larval hematopoietic tissue called the lymph glands (LGs). However, the malignant nature of these cells remains unknown. We aimed to identify if mxcmbn1 LG cells behave as malignant tumor cells and uncover the mechanism(s) underlying the malignancy of the mutant hemocytes. When mutant LG cells were allografted into normal adult abdomens, they continued to proliferate; however, normal LG cells did not proliferate. Mutant circulating hemocytes also attached to the larval central nervous system (CNS), where the basement membrane was disrupted. The mutant hemocytes displayed higher expression of matrix metalloproteinase (MMP) 1 and MMP2 and higher activation of the c-Jun N-terminal kinase (JNK) pathway than normal hemocytes. Depletion of MMPs or JNK mRNAs in LGs resulted in reduced numbers of hemocytes attached to the CNS, suggesting that the invasive phenotype involved elevated expression of MMPs via hyperactivation of the JNK pathway. Moreover, hemocytes with elongated filopodia and extra lamellipodia were frequently observed in the mutant hemolymph, which also depended on JNK signaling. Thus, the MMP upregulation and overextension of actin-based cell protrusions were also involved in hemocyte invasion in mxcmbn1 larvae. These findings contribute to the understanding of molecular mechanisms underlying mammalian leukemic invasion.

Folate deficiency increases the incidence of dolutegravir-associated foetal defects in a mouse pregnancy model

BACKGROUND

Dolutegravir (DTG) is a recommended first-line regimen for all people with Human Immunodeficiency Virus (HIV) infection. Initial findings from Botswana, a country with no folate fortification program, showed an elevated prevalence of neural tube defects (NTDs) with peri-conceptional exposure to DTG. Here we explore whether a low folate diet influences the risk of DTG-associated foetal anomalies in a mouse model.

METHODS

C57BL/6 mice fed a folate-deficient diet for 2 weeks, were mated and then randomly allocated to control (water), or 1xDTG (2.5 mg/kg), or 5xDTG (12.5 mg/kg) both administered orally with 50 mg/kg tenofovir disoproxil fumarate 33.3 mg/kg emtricitabine. Treatment was administered once daily from gestational day (GD) 0.5 to sacrifice (GD15.5). Foetuses were assessed for gross anomalies. Maternal and foetal folate levels were quantified.

FINDINGS

313 litters (103 control, 106 1xDTG, 104 5xDTG) were assessed. Viability, placental weight, and foetal weight did not differ between groups. NTDs were only observed in the DTG groups (litter rate: 0% control; 1.0% 1xDTG; 1.3% 5xDTG). Tail, abdominal wall, limb, craniofacial, and bleeding defects all occurred at higher rates in the DTG groups versus control. Compared with our previous findings on DTG usage in folate-replete mouse pregnancies, folate deficiency was associated with higher rates of several defects, including NTDs, but in the DTG groups only. We observed a severe left-right asymmetry phenotype that was more frequent in DTG groups than controls.

INTERPRETATION

Maternal folate deficiency may increase the risk for DTG-associated foetal defects. Periconceptional folic acid supplementation could be considered for women with HIV taking DTG during pregnancy, particularly in countries lacking folate fortification programs.

FUNDING

This project has been funded by Federal funds from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, under Contract No. HHSN275201800001I and award #R01HD104553. LS is supported by a Tier 1 Canada Research Chair in Maternal-Child Health and HIV. HM is supported by a Junior Investigator award from the Ontario HIV Treatment Network.

Inhibition of matrix metalloproteinases by HIV-1 integrase strand transfer inhibitors

More than fifteen million women with the human immunodeficiency virus type-1 (HIV-1) infection are of childbearing age world-wide. Due to improved and affordable access to antiretroviral therapy (ART), the number of in utero antiretroviral drug (ARV)-exposed children has exceeded a million and continues to grow. While most recommended ART taken during pregnancy suppresses mother to child viral transmission, the knowledge of drug safety linked to fetal neurodevelopment remains an area of active investigation. For example, few studies have suggested that ARV use can be associated with neural tube defects (NTDs) and most notably with the integrase strand transfer inhibitor (INSTI) dolutegravir (DTG). After risk benefit assessments, the World Health Organization (WHO) made recommendations for DTG usage as a first and second-line preferred treatment for infected populations including pregnant women and those of childbearing age. Nonetheless, long-term safety concerns remain for fetal health. This has led to a number of recent studies underscoring the need for biomarkers to elucidate potential mechanisms underlying long-term neurodevelopmental adverse events. With this goal in mind, we now report the inhibition of matrix metalloproteinases (MMPs) activities by INSTIs as an ARV class effect. Balanced MMPs activities play a crucial role in fetal neurodevelopment. Inhibition of MMPs activities by INSTIs during neurodevelopment could be a potential mechanism for adverse events. Thus, comprehensive molecular docking testing of the INSTIs, DTG, bictegravir (BIC), and cabotegravir (CAB), against twenty-three human MMPs showed broad-spectrum inhibition. With a metal chelating chemical property, each of the INSTI were shown to bind Zn++ at the MMP's catalytic domain leading to MMP inhibition but to variable binding energies. These results were validated in myeloid cell culture experiments demonstrating MMP-2 and 9 inhibitions by DTG, BIC and CAB and even at higher degree than doxycycline (DOX). Altogether, these data provide a potential mechanism for how INSTIs could affect fetal neurodevelopment.

HIV-1 Integrase Strand Transfer Inhibitors and Neurodevelopment

Children born to mothers, with or at risk, of human immunodeficiency virus type-1 (HIV-1) infection are on the rise due to affordable access of antiretroviral therapy (ART) to pregnant women or those of childbearing age. Each year, up to 1.3 million HIV-1-infected women on ART have given birth with recorded mother-to-child HIV-1 transmission rates of less than 1%. Despite this benefit, the outcomes of children exposed to antiretroviral drugs during pregnancy, especially pre- and post- natal neurodevelopment remain incompletely understood. This is due, in part, to the fact that pregnant women are underrepresented in clinical trials. This is underscored by any potential risks of neural tube defects (NTDs) linked, in measure, to periconceptional usage of dolutegravir (DTG). A potential association between DTG and NTDs was first described in Botswana in 2018. Incidence studies of neurodevelopmental outcomes associated with DTG, and other integrase strand transfer inhibitors (INSTIs) are limited as widespread use of INSTIs has begun only recently in pregnant women. Therefore, any associations between INSTI use during pregnancy, and neurodevelopmental abnormalities remain to be explored. Herein, United States Food and Drug Administration approved ARVs and their use during pregnancy are discussed. We provide updates on INSTI pharmacokinetics and adverse events during pregnancy together with underlying mechanisms which could affect fetal neurodevelopment. Overall, this review seeks to educate both clinical and basic scientists on potential consequences of INSTIs on fetal outcomes as a foundation for future scientific investigations.

Delta/Notch signaling in glia maintains motor nerve barrier function and synaptic transmission by controlling matrix metalloproteinase expression

We have made a surprising discovery linking Delta/Notch signaling in subperineurial glia (SPG) to the regulation of nerve ensheathment and neurotransmitter release at the Drosophila neuromuscular junction (NMJ). SPG, the counterpart of the endothelial layer in the vertebrate blood–brain barrier, form the key cellular layer that is critical for axonal ensheathment and the blood–brain barrier in Drosophila. Our findings demonstrate that Delta/Notch signaling exerts a constitutive negative inhibition on JNK signaling in SPG, thereby limiting the expression of Mmp1, a matrix metalloproteinase. SPG-specific and temporally regulated knockdown of Delta leads to breakdown of barrier function and compromises neurotransmitter release at the NMJ. Our results provide a mechanistic insight into the biology of barrier function and glia–neuron interactions.

While the role of barrier function in establishing a protective, nutrient-rich, and ionically balanced environment for neurons has been appreciated for some time, little is known about how signaling cues originating in barrier-forming cells participate in maintaining barrier function and influence synaptic activity. We have identified Delta/Notch signaling in subperineurial glia (SPG), a crucial glial type for Drosophila motor axon ensheathment and the blood–brain barrier, to be essential for controlling the expression of matrix metalloproteinase 1 (Mmp1), a major regulator of the extracellular matrix (ECM). Our genetic analysis indicates that Delta/Notch signaling in SPG exerts an inhibitory control on Mmp1 expression. In the absence of this inhibition, abnormally enhanced Mmp1 activity disrupts septate junctions and glial ensheathment of peripheral motor nerves, compromising neurotransmitter release at the neuromuscular junction (NMJ). Temporally controlled and cell type–specific transgenic analysis shows that Delta/Notch signaling inhibits transcription of Mmp1 by inhibiting c-Jun N-terminal kinase (JNK) signaling in SPG. Our results provide a mechanistic insight into the regulation of neuronal health and function via glial-initiated signaling and open a framework for understanding the complex relationship between ECM regulation and the maintenance of barrier function.

Astragalus polysaccharide (APS) exerts protective effect against acute ischemic stroke (AIS) through enhancing M2 micoglia polarization by regulating adenosine triphosphate (ATP)/ purinergic receptor (P2X7R) axis

Clinically, the effective treatment for patients with acute ischemic stroke (AIS) is very limited. Therefore, this paper aims to investigate the mechanism how astragalus polysaccharide (APS) exerts protective effect against AIS and provide a new method for the treatment of AIS. Cell surface antigen flow cytometry and immunofluorescence were used to identify M1 and M2 microglia. Western blot was used to evaluate the expression of associated protein. Oxygen-glucose deprivation (OGD) was used to simulate the effect of AIS on rat microglia. The middle cerebral artery occlusion (MCAO) model was established to simulate the effect of AIS in vivo. Evans blue dye (EBD) was used to evaluate the permeability of blood–brain barrier (BBB). Western blot and cell surface antigen flow cytometry results showed that APS promoted the M2 polarization of rat microglia by inhibiting the expression of purinergic receptor (P2X7R). APS reversed the effect of OGD on the polarization of rat microglia M1/ M2 by regulating P2X7R. APS reversed the effect of MCAO on the polarization of rat microglia M1/ M2 in vivo. Furthermore, APS inhibited the expression of P2X7R by promoting the degradation of adenosine triphosphate (ATP) in the cerebral cortex of MCAO rats. In addition, APS contributed to maintain the integrity of BBB. Summarily, APS can reduce brain injury by promoting the degradation of ATP in microglia and inhibiting the expression of P2X7R after AIS.

Dolutegravir Inhibition of Matrix Metalloproteinases Affects Mouse Neurodevelopment

Dolutegravir (DTG) is a first-line antiretroviral drug (ARV) used in combination therapy for the treatment of human immunodeficiency virus type-1 (HIV-1) infection. The drug is effective, safe, and well tolerated. Nonetheless, concerns have recently emerged for its usage in pregnant women or those of child-bearing age. Notably, DTG-based ARV regimens have been linked to birth defects seen as a consequence of periconceptional usages. To this end, uncovering an underlying mechanism for DTG-associated adverse fetal development outcomes has gained clinical and basic research interest. We now report that DTG inhibits matrix metalloproteinases (MMPs) activities that could affect fetal neurodevelopment. DTG is a broad-spectrum MMPs inhibitor and binds to Zn⁺⁺ at the enzyme’s catalytic domain. Studies performed in pregnant mice show that DTG readily reaches the fetal central nervous system during gestation and inhibits MMP activity. Postnatal screenings of brain health in mice pups identified neuroinflammation and neuronal impairment. These abnormalities persist as a consequence of in utero DTG exposure. We conclude that DTG inhibition of MMPs activities during gestation has the potential to affect prenatal and postnatal neurodevelopment.

Blood-Brain Barrier Breakdown in Stress and Neurodegeneration: Biochemical Mechanisms and New Models for Translational Research

Blood-brain barrier (BBB) is a structural and functional element of the neurovascular unit (NVU), which includes cells of neuronal, glial, and endothelial nature. The main functions of NVU include maintenance of the control of metabolism and chemical homeostasis in the brain tissue, ensuring adequate blood flow in active regions, regulation of neuroplasticity processes, which is realized through intercellular interactions under normal conditions, under stress, in neurodegeneration, neuroinfection, and neurodevelopmental diseases. Current versions of the BBB and NVU models, static and dynamic, have significantly expanded research capabilities, but a number of issues remain unresolved, in particular, personification of the models for a patient. In addition, application of both static and dynamic models has an important problem associated with the difficulty in reproducing pathophysiological mechanisms responsible for the damage of the structural and functional integrity of the barrier in the diseases of the central nervous system. More knowledge on the cellular and molecular mechanisms of BBB and NVU damage in pathology is required to solve this problem. This review discusses current state of the cellular and molecular mechanisms that control BBB permeability, pathobiochemical mechanisms and manifestations of BBB breakdown in stress and neurodegenerative diseases, as well as the problems and prospects of creating in vitro BBB and NVU models for translational studies in neurology and neuropharmacology. Deciphering BBB (patho)physiology will open up new opportunities for further development in the related areas of medicine such as regenerative medicine, neuropharmacology, and neurorehabilitation.

Signaling pathways associated with structural changes in varicose veins: a case-control study

INTRODUCTION AND OBJECTIVES

In varicose veins, blood pressure increases in the veins of the lower extremities due to mechanical stimulation and function remodeling. The aim of this study is assessment of Signaling pathways associated with structural changes in varicose veins.

MATERIALS AND METHODS

This pilot study was performed on patients with varicose veins, which had undergone surgery. The healthy tissues from trauma patients or vascular bypass without underlying diseases were used for control samples. Hematoxylin-eosin, trichrome, and elastin staining were used for histopathological examination. The levels of MDA (malondialdehyde), total thiol, SOD (Superoxide dismutase) and NO (nitric oxide) level were measured using Elisa kits to evaluate the oxidative stress level. Gene expression levels of MMP2, MMP9, FOXO3a, APOE and p53 genes were determined using Real-time PCR.

RESULTS

This study showed, the vascular Vein wall changes are visible in vascular collagen staining. Although these changes are observed in the structure of vascular wall collagen fibers, the accumulation of collagen and elastin was increased in the walls of varicose veins compared to the control group. The amount of nitric oxide and thiol were increased in the varicose group (P < 0.0001). The expression of metalloproteinase2 gene associated with extracellular matrix change was increased in varicose veins. However, the amount of metalloproteinase 9 was decreased in this group compared to control group. FOXO3a, APOE Genes were down-regulated in the varicose veins compared to control group, while p53 gene expression was significantly increased in the varicose group (P < 0.0001).

CONCLUSION

This study demonstrated changes in oxidative stress, morphological structure, and aging pathways in varicose when compared to non-varicose veins. The changes in oxidative stress may be associated with the variations in morphological structure and aging pathways which contribute to the pathogenesis of varicose veins.

The Drosophila brain on cocaine at single-cell resolution

Whereas the neurological effects of cocaine have been well documented, effects of acute cocaine consumption on genome-wide gene expression across the brain remain largely unexplored. This question cannot be readily addressed in humans but can be approached using the Drosophila melanogaster model, where gene expression in the entire brain can be surveyed at once. Flies exposed to cocaine show impaired locomotor activity, including climbing behavior and startle response (a measure of sensorimotor integration), and increased incidence of seizures and compulsive grooming. To identify specific cell populations that respond to acute cocaine exposure, we analyzed single-cell transcriptional responses in duplicate samples of flies that consumed fixed amounts of sucrose or sucrose supplemented with cocaine, in both sexes. Unsupervised clustering of the transcriptional profiles of a total of 86,224 cells yielded 36 distinct clusters. Annotation of clusters based on gene markers revealed that all major cell types (neuronal and glial) as well as neurotransmitter types from most brain regions were represented. The brain transcriptional responses to cocaine showed profound sexual dimorphism and were considerably more pronounced in males than females. Differential expression analysis within individual clusters indicated cluster-specific responses to cocaine. Clusters corresponding to Kenyon cells of the mushroom bodies and glia showed especially large transcriptional responses following cocaine exposure. Cluster specific coexpression networks and global interaction networks revealed a diverse array of cellular processes affected by acute cocaine exposure. These results provide an atlas of sexually dimorphic cocaine-modulated gene expression in a model brain.

Morpho-Functional Consequences of Swiss Cheese Knockdown in Glia of Drosophila melanogaster

Glia are crucial for the normal development and functioning of the nervous system in many animals. Insects are widely used for studies of glia genetics and physiology. Drosophila melanogaster surface glia (perineurial and subperineurial) form a blood–brain barrier in the central nervous system and blood–nerve barrier in the peripheral nervous system. Under the subperineurial glia layer, in the cortical region of the central nervous system, cortex glia encapsulate neuronal cell bodies, whilst in the peripheral nervous system, wrapping glia ensheath axons of peripheral nerves. Here, we show that the expression of the evolutionarily conserved swiss cheese gene is important in several types of glia. swiss cheese knockdown in subperineurial glia leads to morphological abnormalities of these cells. We found that the number of subperineurial glia nuclei is reduced under swiss cheese knockdown, possibly due to apoptosis. In addition, the downregulation of swiss cheese in wrapping glia causes a loss of its integrity. We reveal transcriptome changes under swiss cheese knockdown in subperineurial glia and in cortex + wrapping glia and show that the downregulation of swiss cheese in these types of glia provokes reactive oxygen species acceleration. These results are accompanied by a decline in animal mobility measured by the negative geotaxis performance assay.

Cellular mechanisms and molecular signaling pathways in stress-induced anxiety, depression, and blood-brain barrier inflammation and leakage

Depression and anxiety are comorbid conditions in many neurological or psychopathological disorders. Stress is an underlying event that triggers development of anxiety and depressive-like behaviors. Recent experimental data indicate that anxiety and depressive-like behaviors occurring as a result of stressful situations can cause blood-brain barrier (BBB) dysfunction, which is characterized by inflammation and leakage. However, the underlying mechanisms are not completely understood. This paper sought to review recent experimental preclinical and clinical data that suggest possible molecular mechanisms involved in development of stress-induced anxiety and depression with associated BBB inflammation and leakage. Critical therapeutic targets and potential pharmacological candidates for treatment of stress-induced anxiety and depression with associated BBB dysfunctions are also discussed.

Matrix metalloproteinases regulate ECM accumulation but not larval heart growth in Drosophila melanogaster

The Drosophila heart provides a simple model to examine the remodelling of muscle insertions with growth, extracellular matrix (ECM) turnover, and fibrosis. Between hatching and pupation, the Drosophila heart increases in length five-fold. If major cardiac ECM components are secreted remotely, how is ECM "self assembly" regulated? We explored whether ECM proteases were required to maintain the morphology of a growing heart while the cardiac ECM expanded. An increase in expression of Drosophila's single tissue inhibitor of metalloproteinase (TIMP), or reduced function of metalloproteinase MMP2, resulted in fibrosis and ectopic deposition of two ECM Collagens; type-IV and fibrillar Pericardin. Significant accumulations of Collagen-IV (Viking) developed on the pericardium and in the lumen of the heart. Congenital defects in Pericardin deposition misdirected further assembly in the larva. Reduced metalloproteinase activity during growth also increased Pericardin fibre accumulation in ECM suspending the heart. Although MMP2 expression was required to remodel and position cardiomyocyte cell junctions, reduced MMP function did not impair expansion of the heart. A previous study revealed that MMP2 negatively regulates the size of the luminal cell surface in the embryonic heart. Cardiomyocytes align at the midline, but do not adhere to enclose a heart lumen in MMP2 mutant embryos. Nevertheless, these embryos hatch and produce viable larvae with bifurcated hearts, indicating a secondary pathway to lumen formation between ipsilateral cardiomyocytes. MMP-mediated remodelling of the ECM is required for organogenesis, and to prevent assembly of excess or ectopic ECM protein during growth. MMPs are not essential for normal growth of the Drosophila heart.