Oct 20 (Reuters) - U.S. stock indexes opened higher on Wednesday, helped by strong quarterly updates from companies including Anthem and Verizon, although worries about impact of supply chain constraints and inflation on corporate earnings capped gains. The Dow Jones Industrial Average (.DJI) rose 17.85 points, or 0.05%, at the open to 35,475.16. The S&P 500 (.SPX) opened higher by 4.79 points, or 0.11%, at 4,524.42, while the Nasdaq Composite (.IXIC) gained 30.91 points, or 0.20%, to 15,160.00 at the opening bell.