Diuretics are chemical substances used to lower high blood pressure. They act by inhibiting the sodium-potassium-chloride ions symporter. The inhibition of the transport of these ions back into the blood leaves them in the ascending loop of henle(e part of action of diuretics). The macula densa cells of the juxtaglomerular apparatus sense the presence of these ions,especially the chloride ions and respond by producing or synthesizing more prostaglandins(simply because macula densa cells have more cox-2 receptors). Prostaglandins, therefore, cause vasodilation of the afferent arteriole thus increasing the glomerular filtration rate and hence helps in the elimination of the excess ions.In effect, prostaglandins help in the efficient working of diuretics.
however, NSAIDS block the synthesis of these prostaglandins and hence affect the efficiency of diuretics.