Newcastle officials were baffled by claims on Thursday that Manchester United were in advanced talks to sign Bruno, and Howe couldn't have been stronger in his response when he spoke to the media on Friday morning.
Howe says Bruno remains "totally committed" to Newcastle.
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He said: "I don't even know how to respond to that, I don't even think I should because it's a waste of my energy.
"Bruno's our captain, he's fully committed, he's injured at the moment, his only focus is coming back to fitness.”
"I'm not going to be impolite because I don't think it's the forum to do that in for me it's a nonsense story," added Howe, with Newcastle's head coach having become accustomed to his star players being linked with moves away.
"Is it a problem for us? I don't necessarily think it is a problem for us. But it is unwanted news, I suppose, is the best way to put it. You don't want the players distracted but I don't know how much they will absorb that.
"For me, it is not the time to think about it. In the summer, you can understand those stories a little bit more because the transfer window is open.
"To say our captain is in discussions with another club is totally disrespectful to Bruno more than anything else, he is totally committed here."
Newcastle will again be without Bruno for Sunday's Tyne-Wear derby against Sunderland, but Howe is hopeful the midfielder will be ready to return after the international break. That will also be the case with Lewis Miley.
But there is hope that Sandro Tonali will be fit, with Howe hoping the Italian's groin injury "isn't as bad as first feared". Tonali will be closely assessed today ahead of Sunday's game.
Tonali was forced off in the second half of Wednesday night's Champions League defeat to Barcelona.
Howe said: "We'll wait and see. Hopefully not as bad as maybe first feared when I saw him limping off the pitch.
"We'll see how he is today and then make a decision closer to the game."
Howe added: "It will be after the internationals for Lewy. We anticipate he'll be back hopefully after the break.
"Fingers crossed the same for Bruno and also Fabian [Schar]."