Peter Bergold - US grants

DESCRIPTION (provided by applicant): Little is known about the ability of the brain to repair traumatic brain injury (TBI). Drugs have been developed that treat TBI by preventing injury, but to date these drugs have failed clinical trials. As a result, there are no treatments available to the 1.7 million Americans who annually sustain TBI. Recently, however, the FDA-approved drugs, minocycline plus N-acetyl cysteine, have been shown to improve cognition and memory after experimental TBI. The mechanism of how these drugs work is unknown. These observations provide the justification for the long-term goal to improve brain function by repairing, rather than preventing, TBI. This proposal will test a central hypothesis that: Minocycline (MINO) and N-acetyl cysteine (NAC) promote remyelination and improve cognition and memory following TBI. Three specific aims will test this hypothesis: 1) When and where does MINO plus NAC induce remyelination in the controlled cortical impact (CCI) model of TBI? Preliminary data show that CCI produces widespread demyelination of midline white matter structures, and MINO plus NAC has little effect on this demyelination. Within 2 weeks, MINO plus NAC treatment increased myelin content in previously demyelinated white matter tracts. 2) Which cell types are modulated by MINO plus NAC? Preliminary data indicate that MINO plus NAC modulate microglial polarity in injured white matter by increasing the numbers of anti-inflammatory, tissue-remodeling M2 microglia while decreasing pro-inflammatory M1 microglia. MINO plus NAC also induce oligodendrocytes to increase myelin content in demyelinated white matter. 3) Does remyelination improve cognition and memory? Preliminary data show that CCI prevents acquisition and long-term retention of an active place avoidance task. Both acquisition and retention are improved by MINO plus NAC treatment. Preliminary data also show that an unilateral stereotaxic injection of lysophosphotidylcholine (LPC) into the fimbria produces a localized demyelination and cognitive deficits similar to CCI. Unlike CCI, the LPC-demyelinated fimbria spontaneously remyelinates. Remyelination of the fimbria is accompanied by reversal of the cognition deficits produced by demyelination. This proposed research is both innovative and significant because it explores the novel finding that the ability to remyelinate is not lost following TBI and can be restored with drugs. If successful, the proposed experiments will substantively increase our knowledge of the pathophysiology of TBI as well as provide important information on the drug action of MINO and NAC. The safety and efficacy of MINO and NAC are well-established because both drugs are FDA-approved for uses other than TBI and are in clinical trials, as single drugs, for a variety of brain diseases. The re-use of FDA-approved drugs is perhaps the fastest route to get new drugs to treat TBI into clinical trials. Ultimately, the knowledge gained from this proposal has the potential to greatly improve quality of life after traumatic brain injury.

Therapeutic time window is a key element of any drug to treat TBI. Patients with moderate to severe TBI can be  treated  hours after  injury;?  those  with  mild  TBI  may  delay  treatment  for  days  until  their  symptoms  do  not abate.  Few drugs have been developed with therapeutic time windows long enough to treat TBI, in part, because little  is  known  about  which  cellular  functions  can  be  targeted  by  drugs  dosed  hours  to  days  post-­injury  (PI).  The  combination  of  minocycline  (MINO)  plus  N-­acetylcysteine  (NAC)  retains  high  potency  when  first  dosed  12h  PI  (MN12). Published and preliminary data suggest that MN12 prevents neuronal loss and protects dendrites in the  hippocampal  ipsilateral  to  the  impact  site,  allows  learning  of  an  active  place  avoidance  task  that  requires both  hippocampi;? and restores late long-­term potentiation (LTP) to both hippocampi. Preliminary data suggests that  a  first  dose  of  MINO  plus  NAC  at  72H  PI  (MN72)  is  less  potent  than  MN12  yet  restores  acquisition  of  Barnes  maze, a task that requires only one hippocampus, and late LTP in the hippocampus contralateral to the impact  site. MN72 also increases protein synthesis in the contralateral hippocampus. This proposal examines if MN12  and  MN72 target dendrites,  synapses,  spines,  and  synaptic  protein  synthesis after  closed head  injury  (CHI)  in  mice.  Proposed  studies  will  examine  whether  MN12  and  MN72  target protein  kinase  M  zeta  (PKMz?),  which  is  essential for late LTP and retention of hippocampal-­dependent tasks. Studies will also examine whether MINO  plus  NAC  remains  potent  when  dosed  later  than  72H  PI.  These  data  support  3  specific  aims  (SA)  that  test  a  central hypothesis that: Dosing of MINO plus NAC at clinically relevant therapeutic time windows limits  gray matter injury and improves cognition and memory. SA1: Where does a first dose of MINO plus NAC  at 12 or 72h after CHI repair dendrites, spines and synapses? The working hypothesis of SA1 is that MN12  acts bilaterally to prevent injury and induce repair while MN72 acts only on the contralateral hippocampus. SA1  will  also  assay  neuroinflammation,  oxidative  stress  and  mitochondrial  morphology  after  MN12  or  MN72  treatment.  SA2:  Does  MN12  and  MN72  target  PKMz?  expression  to  restore  synaptic  plasticity  and  acquisition  of  hippocampal-­dependent  tasks?  SA2  will  examine  a  role  for  PKMz?  expression  by  MN12  or  MN72 using NTSA, a novel and specific inhibitor of PKMz?, or in conditional PKMz? mutant mice. SA2 is predicted  to show that MN12 or MN72 target PKMz? to restore late LTP and long-­term memory. SA 3: Does MINO plus  NAC limits brain injury and restore function in the subacute (14D PI) or chronic (45D PI) stages of TBI?  The  utility  of  MINO  plus  NAC  would  be  greatly  increased  if  the  drugs  retained  potency  when  dosed  in  later  phases  of  TBI.  These  studies  have  high  potential  significance  since  they  show  that  a  combination  of  FDA-­ approved  drugs  with  clinically  useful  windows  can  restore  cognition  and  memory,  which  are  central  deficits  produced by TBI. These studies have potentially high impact since the absence of effective drugs make people  with TBI less likely to seek treatment. MN12 and MN72 are attractive candidates for clinical trials to treat TBI.