What is LPS (not just what does it stand for)

Paper link   -     https://www.jneurosci.org/content/40/8/1756.long

Neuronal Mitochondria Modulation of LPS-Induced Neuroinflammation

• What is LPS (not just what does it stand for)? Why is it used as a model for neuroinflammation?
• Describe microglia: where are they found, what role do they play, why can't that role be carried out the same way it is in the rest of the body?
• Mitofusin2 (Mfn2) is a mitochondrial protein. What is its apparent role? Can you think of a reason why overexpression could be protective against a stress? Is it reasonable that overexpression of this gene could also cause problems (if so, how)?
• How did the authors arrange that Mfn2 was only upregulated in the brain and spinal cord of TMFN mice, and not in other tissues of the mice? How do they demonstrate this?
• Briefly describe the roles of these molecules in immunity/inflammation:
  
  IL-1β
  IL-6
  IL-10
  TNFα 
  
  They all belong to a class of molecules; what is that class called?
• What evidence do the authors provide that microglia are not "activated" in response to LPS challenge in TMFN mice? What is the difference (in this paper, in terms of what they represent) between the roles of Iba1 and GFAP?
• Do mitochondria of TMFN mice respond differently to LPS insult than those of nontransgenic mice? How do the authors demonstrate this? Name a way this method couldbe subject to bias on the part of the experimenter, and how one might avoid such bias.
• What does CX3CL1 do, normally? How is its expression affected (in terms of RNA and protein quantity) by inflammation in normal mice and in TMFN mice?
• How do the authors investigate the role of CX3CL1 in microglial inflammation and neuron damage? What method(s) do they use to achieve this? 
• Given that the transgene used is onlyupregulated in the brain and spinal cord of TMFN mice, what might account for the TMFN mice having less severe cardiac dysfunction in response to LPS challenge?