scholarly journals Fractalkine-induced microglial vasoregulation occurs within the retina and is altered early in diabetic retinopathy

2020 ◽  
Author(s):  
Samuel A. Mills ◽  
Andrew I. Jobling ◽  
Michael A. Dixon ◽  
Bang V. Bui ◽  
Kirstan A. Vessey ◽  
...  
Keyword(s):  
Blood Flow ◽  
Diabetic Retinopathy ◽  
Neurovascular Unit ◽  
Renin Angiotensin System ◽  
Retinal Blood Flow ◽  
Early Diabetes ◽  
Angiotensin System ◽  
Ras Pathway ◽  
Vascular Regulation ◽  
The Brain

AbstractLocal blood flow control within the CNS is critical to proper function and is dependent on coordination between neurons, glia and blood vessels. Macroglia such as astrocytes and Müller cells, contribute to this neurovascular unit within the brain and retina, respectively. This study explored the role of microglia, the innate immune cell of the CNS, in retinal vasoregulation and highlights changes during early diabetes. Structurally, microglia were found to contact retinal capillaries and neuronal synapses. In the brain and retinal explants, the addition of fractalkine, the sole ligand for monocyte receptor Cx3cr1, resulted in capillary constriction at regions of microglial contact. This vascular regulation was dependent on microglial involvement, since mice lacking Cx3cr1, exhibited no fractalkine-induced constriction. Analysis of the microglial transcriptome identified several vasoactive genes, including angiotensinogen, a constituent of the renin-angiotensin system (RAS). Subsequent functional analysis showed that RAS blockade via candesartan, abolished microglial-induced capillary constriction. Microglial regulation was explored in a rat streptozotocin (STZ) model of diabetic retinopathy. Retinal blood flow was reduced after 4 weeks due to reduced capillary diameter and this was coincident with increased microglial association. Functional assessment showed loss of microglial-capillary response in STZ-treated animals and transcriptome analysis showed evidence of RAS pathway dysregulation in microglia. While candesartan treatment reversed capillary constriction in STZ-treated animals, blood flow remained decreased likely due to dilation of larger vessels. This work shows microglia actively participate in the neurovascular unit, with aberrant microglial-vascular function possibly contributing to the early vascular compromise during diabetic retinopathy.Significance StatementThis work identifies a novel role for microglia, the innate immune cells of the CNS, in the local control of the retinal vasculature and identifies deficits early in diabetes. Microglia contact neurons and vasculature and express several vasoactive agents. Activation of microglial fractalkine-Cx3cr1 signalling leads to capillary constriction and blocking the renin-angiotensin system (RAS) with candesartan abolishes microglial-mediated vasoconstriction in the retina. In early diabetes, reduced retinal blood flow is coincident with capillary constriction, increased microglial-vessel association, loss of microglial-capillary regulation and altered microglial expression of the RAS pathway. While candesartan restores retinal capillary diameter early in diabetes, targeting of microglial-vascular regulation is required to prevent coincident dilation of large retinal vessels and reduced retinal blood flow.

scholarly journals Fractalkine-induced microglial vasoregulation occurs within the retina and is altered early in diabetic retinopathy

2021 ◽  
Vol 118 (51) ◽  
pp. e2112561118
Author(s):  
Samuel A. Mills ◽  
Andrew I. Jobling ◽  
Michael A. Dixon ◽  
Bang V. Bui ◽  
Kirstan A. Vessey ◽  
...  
Keyword(s):  
Blood Flow ◽  
Diabetic Retinopathy ◽  
Vascular Function ◽  
Immune Cell ◽  
Neurovascular Unit ◽  
Retinal Blood Flow ◽  
Proper Function ◽  
Early Diabetes ◽  
Vascular Regulation ◽  
The Brain

Local blood flow control within the central nervous system (CNS) is critical to proper function and is dependent on coordination between neurons, glia, and blood vessels. Macroglia, such as astrocytes and Müller cells, contribute to this neurovascular unit within the brain and retina, respectively. This study explored the role of microglia, the innate immune cell of the CNS, in retinal vasoregulation, and highlights changes during early diabetes. Structurally, microglia were found to contact retinal capillaries and neuronal synapses. In the brain and retinal explants, the addition of fractalkine, the sole ligand for monocyte receptor Cx3cr1, resulted in capillary constriction at regions of microglial contact. This vascular regulation was dependent on microglial Cx3cr1 involvement, since genetic and pharmacological inhibition of Cx3cr1 abolished fractalkine-induced constriction. Analysis of the microglial transcriptome identified several vasoactive genes, including angiotensinogen, a constituent of the renin-angiotensin system (RAS). Subsequent functional analysis showed that RAS blockade via candesartan abolished microglial-induced capillary constriction. Microglial regulation was explored in a rat streptozotocin (STZ) model of diabetic retinopathy. Retinal blood flow was reduced after 4 wk due to reduced capillary diameter and this was coincident with increased microglial association. Functional assessment showed loss of microglial–capillary response in STZ-treated animals and transcriptome analysis showed evidence of RAS pathway dysregulation in microglia. While candesartan treatment reversed capillary constriction in STZ-treated animals, blood flow remained decreased likely due to dilation of larger vessels. This work shows microglia actively participate in the neurovascular unit, with aberrant microglial–vascular function possibly contributing to the early vascular compromise during diabetic retinopathy.

The renin-angiotensin system and the retinal neurovascular unit: A role in vascular regulation and disease

2019 ◽  
Vol 187 ◽  
pp. 107753 ◽  
Author(s):  
Joanna A. Phipps ◽  
Michael A. Dixon ◽  
Andrew I. Jobling ◽  
Anna Y. Wang ◽  
Ursula Greferath ◽  
...  
Keyword(s):  
Neurovascular Unit ◽  
Renin Angiotensin System ◽  
Angiotensin System ◽  
Renin Angiotensin ◽  
Vascular Regulation

scholarly journals Divergent mechanism regulating fluid intake and metabolism by the brain renin-angiotensin system

2012 ◽  
Vol 302 (3) ◽  
pp. R313-R320 ◽  
Author(s):  
Curt D. Sigmund
Keyword(s):  
Blood Pressure ◽  
Fluid Intake ◽  
Renin Angiotensin System ◽  
Metabolic Effects ◽  
Angiotensin System ◽  
Renin Angiotensin ◽  
Intracellular Form ◽  
Efferent Pathways ◽  
The Brain ◽  
Pituitary Adrenal Axis

The purpose of this review is two-fold. First, I will highlight recent advances in our understanding of the mechanisms regulating angiotensin II (ANG II) synthesis in the brain, focusing on evidence that renin is expressed in the brain and is expressed in two forms: a secreted form, which may catalyze extracellular ANG I generation from glial or neuronal angiotensinogen (AGT), and an intracellular form, which may generate intracellular ANG in neurons that may act as a neurotransmitter. Second, I will discuss recent studies that advance the concept that the renin-angiotensin system (RAS) in the brain not only is a potent regulator of blood pressure and fluid intake but may also regulate metabolism. The efferent pathways regulating the blood pressure/dipsogenic effects and the metabolic effects of elevated central RAS activity appear different, with the former being dependent upon the hypothalamic-pituitary-adrenal axis, and the latter being dependent upon an interaction between the brain and the systemic (or adipose) RAS.

The Brain-Renin-Angiotensin System: Update

1986 ◽  
pp. 123-133 ◽  
Author(s):  
Thomas Unger ◽  
Detlev Ganten ◽  
Gerald Ludwig ◽  
Rudolf E. Lang
Keyword(s):  
Renin Angiotensin System ◽  
Angiotensin System ◽  
Renin Angiotensin ◽  
The Brain

The renin angiotensin system and the brain: New developments

2017 ◽  
Vol 46 ◽  
pp. 1-8 ◽  
Author(s):  
Ehab Farag ◽  
Daniel I. Sessler ◽  
Zeyd Ebrahim ◽  
Andrea Kurz ◽  
Joseph Morgan ◽  
...  
Keyword(s):  
Renin Angiotensin System ◽  
Angiotensin System ◽  
New Developments ◽  
Renin Angiotensin ◽  
The Brain

scholarly journals Bidirectional asymmetry in the neurovisceral communication for the cardiovascular control: New insights

2017 ◽  
Vol 51 (3) ◽  
pp. 157-167 ◽  
Author(s):  
I Prieto ◽  
AB Segarra ◽  
M Martinez-Canamero ◽  
M De Gasparo ◽  
S Zorad ◽  
...  
Keyword(s):  
Essential Role ◽  
Renin Angiotensin System ◽  
Cardiovascular Function ◽  
Cardiovascular Control ◽  
Functional Connection ◽  
Angiotensin System ◽  
Positive Correlations ◽  
Available Information ◽  
The Brain

AbstractThe cardiovascular control involves a bidirectional functional connection between the brain and heart. We hypothesize that this connection could be extended to other organs using endocrine and autonomic nervous systems (ANS) as communication pathways. This implies a neuroendocrine interaction controlling particularly the cardiovascular function where the enzymatic cascade of the renin-angiotensin system (RAS) plays an essential role. It acts not only through its classic endocrine connection but also the ANS. In addition, the brain is functionally, anatomically, and neurochemically asymmetric. Moreover, this asymmetry goes even beyond the brain and it includes both sides of the peripheral nervous and neuroendocrine systems. We revised the available information and analyze the asymmetrical neuroendocrine bidirectional interaction for the cardiovascular control. Negative and positive correlations involving the RAS have been observed between brain, heart, kidney, gut, and plasma in physiologic and pathologic conditions. The central role of the peptides and enzymes of the RAS within this neurovisceral communication, as well as the importance of the asymmetrical distribution of the various RAS components in the pathologies involving this connection, are particularly discussed. In conclusion, there are numerous evidences supporting the existence of a neurovisceral connection with multiorgan involvement that controls, among others, the cardiovascular function. This connection is asymmetrically organized.

Brain renin-angiotensin system and sympathetic hyperactivity in rats after myocardial infarction

1999 ◽  
Vol 276 (5) ◽  
pp. H1608-H1615 ◽  
Author(s):  
Weiguo Zhang ◽  
Bing S. Huang ◽  
Frans H. H. Leenen
Keyword(s):  
Renin Angiotensin System ◽  
Coronary Artery Ligation ◽  
Arterial Baroreflex ◽  
Baroreflex Control ◽  
Angiotensin System ◽  
Sympathetic Hyperactivity ◽  
Renin Angiotensin ◽  
Air Jet ◽  
Baroreflex Function ◽  
The Brain

Blockade of brain “ouabain” prevents the sympathetic hyperactivity and impairment of baroreflex function in rats with congestive heart failure (CHF). Because brain “ouabain” may act by activating the brain renin-angiotensin system (RAS), the aim of the present study was to assess whether chronic treatment with the AT1-receptor blocker losartan given centrally normalizes the sympathetic hyperactivity and impairment of baroreflex function in Wistar rats with CHF postmyocardial infarction (MI). After left coronary artery ligation (2 or 6 wk), rats received either intracerebroventricular losartan (1 mg ⋅ kg−1 ⋅ day−1, CHF-Los) or vehicle (CHF-Veh) by osmotic minipumps. To assess possible peripheral effects of intracerebroventricular losartan, one set of CHF rats received the same rate of losartan subcutaneously. Sham-operated rats served as control. After 2 wk of treatment, mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA) at rest and in response to air-jet stress and intracerebroventricular injection of the α2-adrenoceptor-agonist guanabenz were measured in conscious animals. Arterial baroreflex function was evaluated by ramp changes in MAP. Compared with sham groups, CHF-Veh groups showed impaired arterial baroreflex control of HR and RSNA, increased sympathoexcitatory and pressor responses to air-jet stress, and increased sympathoinhibitory and hypotensive responses to guanabenz. The latter is consistent with decreased activity in sympathoinhibitory pathways. Chronic intracerebroventricular infusion of losartan largely normalized these abnormalities. In CHF rats, the same rate of infusion of losartan subcutaneously was ineffective. In sham-operated rats, losartan intracerebroventricularly or subcutaneously did not affect sympathetic activity. We conclude that the chronic increase in sympathoexcitation, decrease in sympathoinhibition, and desensitized baroreflex function in CHF all appear to depend on the brain RAS, since this whole pattern of changes can be normalized by chronic central AT1-receptor blockade with losartan.

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