Compositions for inhibiting the aggregation of a granin from a non-toxic low molecular weight form to a toxic high molecular weight aggregated form and/or dissociating a high molecular weight aggregated form to a low molecular weight form are provided. Such a composition typically includes one or more active compounds or agents, which may also be referred to herein as disaggregation compounds. Using the compounds and compositions described herein, methods of i) modulating, inhibiting or preventing the interaction of granins with metal ions, ii) modulating, inhibiting, preventing the aggregation of granins or dissociating aggregated granins, iii) reducing or inhibiting cell toxicity, iv) treating or preventing dementia or Alzheimer's disease, and v) preventing or treating Parkinson's and/or Huntington's diseases are also provided.