The Conference B leader had won the past four meetings between the teams but paid the price for poor discipline this time out, with Cian Healy and Tadhg Furlong both sent to the sin-bin inside the first half-hour of the fixture.
Furlong was still off the field when Lowe was shown a red card for taking out Andrew Conway as the Munster player attempted to claim a high kick, the challenge seeing him land on his head as he was flipped in the air.
Chris Cloete scored a try before being carried off on a stretcher while Keith Earls intercepted a pass to reach the line for the hosts, who relied on Joey Carbery's boot — the five-eighth kicked 14 points against his former team — to secure a 26-17 win.
Scarlets also saw an impressive streak of their own come to an emphatic halt as it lost at home for the first time in 27 games, going down 34-5 to Cardiff Blues in a one-sided Welsh derby.
Ray Lee-Lo grabbed two of the visiting team's four tries, Gareth Anscombe securing the additional bonus point in the closing stages when he picked off a pass to score.
Edinburgh retained the 1872 Cup with a game to spare thanks to a hard-fought 16-8 victory away at Glasgow.
Jaco van der Walt kicked 11 points, including converting Stuart McInally's try, as the visitors prevailed at Scotstoun Stadium, with Conference A leader Glasgow even missing out on a losing bonus when Adam Hastings was unable to add the extras after George Horne had touched down.
Edinburgh had won 23-7 against the same opponent in the first meeting of the best-of-three series last week, although it still remains fifth in Conference B.
Benetton came out on top in the all-Italian clash with Zebre, triumphing 28-10 to complete the double over its compatriots.
Having triumphed 10-8 in the previous meeting of the teams in Parma, Benetton managed three tries — Luca Bigi, Federico Ruzza and Michele Lamaro the scorers — to run out a comfortable winner at Stadio Monigo.