Lecture 3: Microglia + Neuroinflammation + PUFAs + Fat-1 + BDNF + Neurogenesis + Pathways + Cells

CNS Lipids + Inflammation

SSRI/SNRI, SSRE, NDRI/SGAs, Omega-3/PUFAs -> anti-inflammation

NDRIs

NE-Dopamine Reuptake Inhibitors -> keep NTs in the synapse

SGAs

second generation antipsychotics

SSRE

selective serotonin reuptake enhancer

Microglia

Iba-1/CD11B markers, act like immune cells, not part of NS, invade brain + monitor synapses

Microglia Ligands/Receptors

PAMPs (LPS) + DAMPS (ATP) -> TLR (toll-like) + ATPR

M1 Microglia

LPS/IFN-𝛾 -> M1 -> IL-1B/IL-6/TNF-a/CCL2/ROS/NO/ 2-AG; pro-inflammatory, kill neurons

M2 Microglia

IL-4/IL-13 -> M2 -> IL-10 + resolvin D1 + lipoxin A4; anti-inflammatory, healthy brain

Resolvin D1/Lipoxin A4

prevent apoptosis + reduce oxidative stress by consuming ROS

TSPO

marker for mitochondria, found in microglia cells; expect to see increase TSPO in M1 microglial cells

Neuroinflammation Model

induced by intracerebroventricular delivery of LPS; induces inflammation

Neuroinflammation Mechanism

activates HPA axis + M1 microglia -> induces anxiety + depression behaviour, impairs memory, dysfunction of NTs, serotonergic neuron loss in hippocampus + Raphe nucleus

PUFAs

n-3 PUFA inhibit n-6 FA arachidonic acid -> eicosanoid (pro-inflammatory via cyclo/lipoxygenase

Oral Delivery of PUFA

didn’t know how much was in brain, or converted in BBB

Fat-1 Mice

carry Fat-1 transgenic from Caenorhabditis roundworm, convert n-6 -> n-3; no inflammation

Fat-1 Experiment

surgery (LPS injection) -> rest -> LPS (M1 recognition) -> SPT, TST, FST -> tissue collection

Fat-1 Experimental Groups

WT/saline (no Fat, n-6), Fat-1Saline (Fat), WT/LPS (n-6, LPS), Fat-1/LPS (Fat, n-3)

Fat-1 Results

decrease SPT, increase immobility TST, increase iNOS/NO, decrease BDNF/TrkB (WT/LPS)

iNOS/NO

inducible nitric oxide synthase -> produces NO; NO by M1 pro-inflammatory response

Fat-1/LPS

100% converts n-6 -> n-3; should be above control for BDNF levels

TrkB Protein

BDNF receptor, decrease in both WT/LPS + Fat-1/LPS; why?

Ketosis Molecular Involvements

mitochondria (oxidative phosphorylation) + FFA/glycerol (ketone bodies)

BDNF Importance

antidepressants -> downstream -> turn on BDNF gene; neurogenesis/survival;

BDNF Detection

detect increase in phosphoCREB -> know we have enough BDNF; ser133 phosphorylation

Depression Theories

NT decrease, neuroinflammation increase, BDNF decrease; physical volume changes???

Neurogenesis Theory

declines w/age ( not be expected), disrupted in ND disease, enhancing can rescue memory

Neurogenesis

young neurons = excitability/plasticity; adult neurons activated by learning, help memory

Neurogenesis Location

subgranular zone (SGZ) + subventricular zone; progenitor -> differentiate -> circuit in DG

Neurogenesis Process

proliferation -> differentiation -> survival w/ BDNF -> neural circuit -> hippocampus DG

Neurogenesis Duration

about 2-4 week; why antidepressants reboots neurogenesis; don’t feel good till 2-4w

ADM/Neurogenesis

decrease in neurogenesis in induced models, increase with fluoxetine; 2-3 weeks

BDNF Role

enhancing monoaminergic = increase BDNF -> deletes structural effects (increases neurogenesis)

Neurotrophin Signalling

mitogen activated protein kinase (MAPK); PI3 Kinase, Phospholipase C𝛾 pathways

MAPK Pathway

BDNF -> Trk -> ras -> raf -> MAPKK (MEK) -> MAPK (Erk) -> rsk/msk -> CREB

PI3 Kinase Pathway

BDNF -> Trk -> P13Kinase -> PDK -> AKT -> lxB -> inhibit apoptosis -> neural targets

Phospholipase Pathway

BDNF -> Trk -> PLC -> IP3 + DAG -> PKC -> raf -> MAPK pathway

Stress + ADM

opposing effects; 1) neurogenesis in SGZ, 2) VEGF/BDNF in HC; increases proliferation/survival

Neurogenesis Mechanism

radial-like glial cell -> IPC -> neuroblast -> immature DGC -> mature neuron

Radial-Like Glial Cell

in SGZ, GFAP+ and Nestin; TKTL1 (energy pathway), Notch2NL

Immature Neuron

NR1/NR2B+, DCX and NKCC1 (co-transporter)

Mature Neuron

DG markers, 3-4 weeks, NR1/NR2A+, Calbindin CaBP, KCC2 (co-transporter), MAP2

BrdU

thymine analog; detects DNA; marker for neurogenesis/dividing DNA/cells; Edu safer/less toxic

DCX

doublecortin, marker for neurogenesis + neuronal migration + immature DGC

Exercise/Cell Survival

in exercising mice, BrdU detection -> more cell proliferation = more cell survival

Stress Causes

inflammation -> monoamine metabolism, neural damage, immune cells, microglia activation

Monoamine Metabolism

5HT (serotonin), DA, NE, IDO

IDO

indoleamine 2, 3-dioxygenase; activated by stress, breaks down tryptophan, precursor for NTs; not good

Inflammation Cytokines

IL-6, TNF-a, IL-1, iNOS, ROS; by immune cells; increase in activity

Neural Damage

neurotrophic factors; make neurons smaller, less synaptic connections

Schizophrenia/BDNF/Exercise

exercise -> myokines (irisin/IGF-1/VEGF) + adipokines (remodel fat cells) IL-10 -> benefit brain -> plasticity, remodeling, learning and memory

TKTL1

pseudogene; links pentose phosphate (CREB) pathway, non-oxidative glucose pathway -> glycolysis; generates sugar phosphates for nucleotide metabolism + production of NADPH, reducing agent/antioxidant

Notch2NL

human specific, radial glial cells; autism, schizophrenia, microcephaly; Arg now, Lys before