Wynn Resorts Ltd. co-founder Elaine Wynn Wednesday denied the casino operator’s accusations of improper activity and sought shareholders’ support to keep her board seat. Ms. Wynn, the company’s third-largest shareholder, said in a letter to shareholders that the board “has repeatedly presented a number of insinuations that are without factual basis” and that it was going to “reckless lengths” to exclude her as a director.