Research

THE ROLE OF PERIPHERAL SERUM AMYLOID A ON BRAIN INFLAMMATION AFTER TBI

THE ROLE OF MICROBIOME IN THE NEUROPATHOLOGY OF TRAUMATIC BRAIN INJURY

TARGETING SERUM AMYLOID A AS A PREVENTATIVE MEASURE FOR THE ONSET OF ALZHEIMER´S DISEASE AFTER HEAD INJURY.

Traumatic Brain Injury (TBI) triggers a loss of brain tissue and, subsequently, a strong inflammatory response in the brain. In addition, TBI can alter the function of peripheral regions and other organs, eliciting systemic responses and global consequences.

A focal injury to the brain elicits a rapid hepatic response, the production of chemokines by the liver acts as an amplifier of the focal injury response providing a route of CNS-liver communication. However, little is currently known regarding the inflammatory mediators and acute-phase proteins involved in the peripheral regions after brain injury, such as the liver. Furthermore, the extent of damage TBI inflicts on the peripheral organs remains largely unexplored.

Serum Amyloid A1 (SAA1) is an acute phase protein involved in the chemotactic recruitment of inflammatory cells to the site of inflammation. After tissue damage, SAA1 is mainly produced in the liver and exported via peripheral circulation, directly affecting the pathogenesis of inflammation in other organs. The role of SAA1 after TBI is unknown, however, we have recently shown that TBI induces the production and release of SAA1 from the liver into the circulatory system, and our preliminary data will show that SAA1 relocates to the brain lesion where it interacts with microglial cells.

We will test the hypothesis that hepatic SAA1 exacerbates the brain’s inflammatory response to TBI, leading to enhanced cell death, inflammation and behavioral deficits.

1) Determine the effect of TBI severity on SAA1 expression in periphery and in the brain;

2) Investigate whether peripherally-produced SAA1 stimulates neuroinflammation, neuronal damage and behavioral dysfunction after TBI.

Neural Regen Res. 2016 Feb;11(2):226-7

In conclusion, since inflammation appears to be a common link between brain injury and the periphery, one is led to hypothesize that inflammatory signals released after TBI could regulate components of hepatic response and that consequently induce detrimental changes damaged brain regions. As an acute phase protein with pleiotropic pro-inflammatory properties, SAA1 may represent an important link between brain injury and hepatic and systemic inflammation. Elucidation of the role SAA1 plays in the general inflammatory response after TBI will aid in the design of more efficient therapeutic approaches for acute inflammation, using agents that most effectively suppress SAA1 and mitigating subsequent, secondary brain injury.

Research Topics

https://orcid.org/0000-0002-6174-4113

KEYWORDS / AREAS OF INTEREST

· Brain damage: excitotoxicity, cerebral ischemia, stroke, traumatic brain injury, neonatal and adult.

· Neuroinflammation: microglia activation, astrogliosis, cytokines, oxidative stress, gliosis, sex-differences, trauma, macrophages, cerebral blood flow, cerebral edema, hypertension, vasculature, glial scar, TGFbeta, smad3, NOS.

· Neurodegeneration and neurogenesis: apoptosis, necrosis, neurorestoration, neuronal injury, proliferation, oligodendrocytes, caspase-3, PPARgamma,

· Neuroprotection and neurorestauration: angiotensin receptor blockers, melatonin, ApoE genotype, sartans, inhaled nitric oxide, candesartan, telmisartan, antisense therapy.

· Brain-periphery axis: hepatic inflammation, acute phase proteins, serum amyloid A, systemic inflammation, brain-liver axis, brain-gut axis, microbiome

LABORATORY TECHNIQUES AND SKILLS

Molecular biology: Agarose gels, RT-PCR, SDS-PAGE, immunoblotting, protein quantification and biotin labeling, cell transfection, Caspase Activity, DNA/RNA isolation, RT-PCR, microarray PCRs, ELISA.

Tissue culture: Embryonic/postnatal primary cultures (cortical astrocytes, microglial and neurons), Adenohypophysis primary cultures, Cells lines: HEK293, GH4C4, Cell line transfection.

Histology and in situ hybridation: Vibratome/cryostat/microtome tissue sectioning, fixing tissue, histochemistry and immunofluorescence (single-double label), histological techniques, Golgi staining, in situ hybridation combined with immunohistochemistry, TUNEL cell death assay.

Microscopy/Imaging: Light/Bright-field microscopy, Fluorescence microscopy, Confocal Microscopy and MRI.

Animal models and Behavioral test: Excitotoxic, traumatic, and ischemic models in mice and rats. Injections; intracerebral/intraventricular, intraperitoneal, subcutaneous, orally by gavage. Cerebral blood flow and blood pressure measurements by tail-cuff method. Breeding mice. Rat/Mouse anatomy/microanatomy: CNS, Stereotaxic surgery, Dissection/brain dissection, Intracardial perfusion. Behavioral; motor function and cognitive tests.

Computer skills: Windows, Mac OSX, MS Office, Prism, SPSS, Adobe Photoshop, Adobe Illustrator, Corel Draw, Page Master, EndNote, Stereo Investigator.

Gut microbiota are an essential neuromodulator of gut-brain axis signaling and can impact brain inflammation and outcome after ischemic injury. Several studies have shown that microbiota composition, diversity, and richness can influence anxiety- and depressive-like behaviors.

Recently, we have focused on how TBI affects the function of peripheral systems, and in this project we are studying how TBI alters the microbiome and the resultant impact on TBI-induced affective disorders.

We have previously shown that controlled cortical impact (CCI) in mice induces the development of distinctive depression, anxiety, and schizophrenia behaviors that are independent of injury severity, and our preliminary data will show that CCI causes a rapid shift in microbiota diversity within 24h of TBI, including a dramatic change in the diversity of the psychoactive Lactobacillus family.

Based on our data, we are testing the hypothesis that changes to commensal gut microbiota after TBI modulates brain inflammation, and drives the development of affective disorder phenotypes in mice.

To test our hypothesis, we will:

1) identify differentially abundant bacteria before and after mild and severe control cortical impact (CCI) by 16S and metagenomic analysis;

2) perform rescue experiments with probiotics containing TBI-impacted bacteria; and

3) compare the recovery of germ-free (GF) mice exposed to TBI following either sham or TBI mouse fecal transplants.

The devastating deficiencies that result in the brain from traumatic brain injury (TBI) stem from multiple overlapping mechanisms, exacerbated by the fact that there are no effective treatments.

TBI is recognized as the strongest environmental risk factor for neurodegenerative disease later in life, including dementia of Alzheimer's disease (AD)-type.

Current TBI therapies have not lived up to expectations, investigating novel compounds that address multiple mechanisms is required to pursue neuroprotective efficacy. Serum Amyloid A1 (SAA1) is an acute phase protein involved in the chemotactic recruitment of inflammatory cells to the site of inflammation.

After tissue damage, SAA1 is mainly produced in the liver and exported via peripheral circulation, directly affecting the pathogenesis of inflammation in other organs. We will use a well characterized animal model of TBI to determine the molecular association between SAA1 and Aβ deposition after TBI. This proposal will investigate whether in vivo gene SAA1 silencing improves clearance of soluble Aβ and reduces deposition into the injured brain.

This proposal will expand on these promising preliminary findings, and the hypothesis will be scientifically tested via three specific aims:

(1) determine the cellular source of the SAA1 expression in the injured brain;

(2) examine the association between SAA1 and Aβ deposits in the acute phase post-TBI;

(3) investigate if SAA1 gene silencing reduces Aβ levels and cognitive decline after TBI.

We anticipate that results from this proposal will provide a sound basis for exploring and developing new therapies for individuals developing pathology arising from brain injury to direct targeted strategies for dissolution of the Aβ accumulation through the inhibition of SAA1 following TBI.