Neuroglia, Volume 2, Issue 1 (December 2021) – 9 articles

Inflammation is the cause and/or result of many diseases in peripheral tissues and the central nervous system. Recent findings suggested that inflammation in peripheral tissue induces an inflammatory response in the brain that activates glial cells, which, in turn, induce neuronal cell dysfunction. Therefore, anti-inflammatory compounds are important for the suppression of chronic inflammation and prevention of disease. The present study revealed microglial activation in the hippocampus of the brain two days after the peripheral administration of lipopolysaccharide (LPS). Furthermore, the expression of the synaptic vesicle membrane protein, synaptophysin, in the CA3 stratum lucidum of the hippocampus was down-regulated 7 days after the LPS injection. The administration of tocotrienols, a type of vitamin E, significantly attenuated these changes in the hippocampus. Collectively, the present results demonstrated the spread of peripheral inflammatory responses to the brain, in which glial activation and neuronal dysfunction were induced, while tocotrienols exerted anti-inflammatory effects and protected neurons from damage. Full article

Caveolae are plasma membrane invaginations that are enriched in cholesterol-binding proteins called caveolins. The presence of caveolae and caveolins in mixed cultures of human neurons and glia has not been investigated. Here, we sought to determine the presence of caveolae and caveolins in human NTera-2 (NT2/D1) cells, differentiated with retinoic acid into neuron-like (NT2/N) and astrocyte-like (NT2/A) cells. We found that while caveolin-3 mRNA levels remained relatively constant, caveolin-1 and -2 levels were upregulated in NT2/A and downregulated in NT2/N. No caveolin-1 immunoreactivity was detected in NT2/N. Electron microscopy revealed numerous flask-shaped invaginations (~86–102 nm in diameter) in the plasma membrane of NT2/A and NT2/N cells, while only few were detected in NT2/D1 cells. Immunoelectron microscopy localized caveolin-1 gold particles in the flask-shaped structures on plasmalemma and cytoplasmic vesicles of NT2/A cells. Furthermore, NT2/A endocytosed Alexa 488 conjugated-cholera toxin B subunit (CTX-B) through a caveolae- and clathrin-dependent pathway, whereas NT2/N endocytosed CTX-B through a caveolae-independent pathway. We have established that while NT2/A expressed functional caveolae, the molecular identity of the plasma membrane invaginations in NT2/N is unknown. The expression of caveolin proteins was differentially regulated in these cells. Taken together, our findings support the usefulness of the human NT2 model system to study the role of caveolins in neuron–glia communication, and their involvement in brain health and disease. Full article

Glia, or glial cells, are considered a vital component of the nervous system, serving as an electrical insulator and a protective barrier from the interstitial (extracellular) media. Certain glial cells (i.e., astrocytes, microglia, and oligodendrocytes) within the CNS have been shown to directly affect neural functions, but these properties are challenging to study due to the difficulty involved with selectively-activating specific glia. To overcome this hurdle, we selectively expressed light-sensitive ion channels (i.e., channel rhodopsin, ChR2-XXL) in glia of larvae and adult Drosophila melanogaster. Upon activation of ChR2, both adults and larvae showed a rapid contracture of body wall muscles with the animal remaining in contracture even after the light was turned off. During ChR2-XXL activation, electrophysiological recordings of evoked excitatory junction potentials within body wall muscles of the larvae confirmed a train of motor nerve activity. Additionally, when segmental nerves were transected from the CNS and exposed to light, there were no noted differences in quantal or evoked responses. This suggests that there is not enough expression of ChR2-XXL to influence the segmental axons to detect in our paradigm. Activation of the glia within the CNS is sufficient to excite the motor neurons. Full article

Astrocytes elicit bidirectional control of microvascular diameter in acutely isolated brain slices through vasoconstriction and vasodilation pathways that can be differentially recruited via the free Ca²⁺ concentration in endfeet and/or the metabolic status of the tissue. However, the Ca²⁺-level hypothesis has not been tested using direct manipulation. To overcome this, we used Ca²⁺-clamp whole-cell patching of peri-arteriole astrocytes to change astrocyte-free Ca²⁺ to different concentrations and examined the vascular response. We discovered that clamping Ca²⁺ at the approximate resting value (100 nM) had no impact on arteriole diameter in a pre-constricted arteriole. However, a moderate elevation to 250 nM elicited sustained vasodilation that was blocked by the COX-1 antagonist SC-560 (500 nM). The vasodilation to 250 nM Ca²⁺ was sensitive to the metabolic state, as it converted to vasoconstriction when oxygen tension was dramatically elevated. In normal oxygen, clamping astrocyte Ca²⁺ well above the resting level (750 nM) produced sustained vasoconstriction, which converted to vasodilation in the 20-HETE blocker HET0016 (1 μM). This response was fully blocked by the addition of SC-560 (500 nM), showing that 20-HETE-induced vasoconstriction dominated the dilatory action of COX-1. These data demonstrate that direct changes in astrocyte free Ca²⁺ can control multiple arteriole tone states through different mediators. Full article

Neurovascular coupling is a key control mechanism in cerebral blood flow (CBF) regulation. Importantly, this process was demonstrated to be affected in several neurological disorders, including epilepsy. Neurovascular coupling (NVC) is the basis for functional brain imaging, such as PET, SPECT, fMRI, and fNIRS, to assess and map neuronal activity, thus understanding NVC is critical to properly interpret functional imaging signals. However, hemodynamics, as assessed by these functional imaging techniques, continue to be used as a surrogate to map seizure activity; studies of NVC and cerebral blood flow control during and following seizures are rare. Recent studies have provided conflicting results, with some studies showing focal increases in CBF at the onset of a seizure while others show decreases. In this brief review article, we provide an overview of the current knowledge state of neurovascular coupling and discuss seizure-related alterations in neurovascular coupling and CBF control. Full article

The COVID-19 pandemic has paralleled the great Spanish flu pandemic of 1918–1919 in the United States. Previous historical accounts have strongly suggested a post-viral syndrome and, currently, a post-COVID-19 viral syndrome is unquestionable, which shares many of the characteristics of myalgic encephalomyelitis/chronic fatigue syndrome that is present globally. The original term for this post-acute sequela of SARS-CoV-2 (PASC) was termed long haulers by those who were affected with this syndrome and it is now termed long COVID (LC) or PASC. International researchers and clinicians are desperately trying to better understand the pathobiological mechanisms possibly involved in this syndrome. This review aims to summarize many of the cumulated findings associated with LC/PASC and provides supportive and representative illustrations and transmission electron micrographic remodeling changes within brain tissues associated with a stress type of injury as occurs in the classic db/db and novel BTBR ob/ob obesity and diabetes mellitus mice models. These models are utilized to merely provide a response to metabolic stress injury wound healing mechanisms that are also present in humans. This review posits that neuroglial activation and chronic neuroinflammation may be a common denominator for the development of the complex LC/PASC syndrome following acute COVID-19 due to SARS-CoV-2. Full article