Provided herein are polypeptides containing stabilized BH4 domains of BCL-2 family proteins that are capable of binding and/or inactivating and/or modulating BAX protein, and/or its close homologues BAK and BOK, and/or other physiological BH4 targets. Also provided are compositions containing these polypeptides and methods of treating cytotoxic diseases that include administering to a subject one of the polypeptides.