这句话怎么理解翻译？

NSAIDs inhibit the synthesis of gastroduodenal prostaglandins,
which are centrally important for mucosal protection via
mucus and bicarbonate secretion and mucosal blood flow.
Abrogation of prostaglandin-dependent mechanisms is sufficient
to cause local erosions, which deepen to form ulcers in
the presence of acid and pepsin. A central role for pepsin is
more likely in NSAID ulcers than in ulcers caused by H. pylori,
as much greater changes in pH are needed to prevent damage
or heal ulcers
.

不清楚，红颜色这段话，是定语从句，还是比较。

请各位高手指教帮助。