Shadowrun is one of the most adult themed RPG's out there, the published materials deals with Things like violence, drug use, sex, crime...etc. I remember seeing prices for both high end and low end sexual services on some of the old "Cost of living tables" they used back in 1-3rd edition setting books, and the core rulebook used to have a section about how GM's should agree with their players before playing what kind of adult themes were ok to include in the game, since there are so many ( i can't remember if that section is still in the 5th edition ). So in essence unless you start writing about Things like graphically describing child abuse, then you're good.
Anyways, just put a dsclaimer before your story and it should be fine, then people can choose if they wanna read it. In my personal opinion though, thats not even necessary, as i said SR is an inherently adult themed game.