Aaltonen Niina, Lehtonen Marko, Varonen Katri, Goterris Gemma Arrufat, Laitinen Jarmo T
School of Pharmacy, University of Eastern Finland, P,O, Box 1627, 70211, Kuopio, Finland.
BMC Pharmacol. 2012 Jun 11;12:7. doi: 10.1186/1471-2210-12-7.
Lysophosphatidic acid (LPA) is a signalling phospholipid with multiple biological functions, mainly mediated through specific G protein-coupled receptors. Aberrant LPA signalling is being increasingly implicated in the pathology of common human diseases, such as arteriosclerosis and cancer. The lifetime of the signalling pool of LPA is controlled by the equilibrium between synthesizing and degradative enzymatic activity. In the current study, we have characterized these enzymatic pathways in rat brain by pharmacologically manipulating the enzymatic machinery required for LPA degradation.
In rat brain cryosections, the lifetime of bioactive LPA was found to be controlled by Mg2+-independent, N-ethylmaleimide-insensitive phosphatase activity, attributed to lipid phosphate phosphatases (LPPs). Pharmacological inhibition of this LPP activity amplified LPA1 receptor signalling, as revealed using functional autoradiography. Although two LPP inhibitors, sodium orthovanadate and propranolol, locally amplified receptor responses, they did not affect global brain LPA phosphatase activity (also attributed to Mg2+-independent, N-ethylmaleimide-insensitive phosphatases), as confirmed by Pi determination and by LC/MS/MS. Interestingly, the phosphate analog, aluminium fluoride (AlFx-) not only irreversibly inhibited LPP activity thereby potentiating LPA1 receptor responses, but also totally prevented LPA degradation, however this latter effect was not essential in order to observe AlFx--dependent potentiation of receptor signalling.
We conclude that vanadate- and propranolol-sensitive LPP activity locally guards the signalling pool of LPA whereas the majority of brain LPA phosphatase activity is attributed to LPP-like enzymatic activity which, like LPP activity, is sensitive to AlFx- but resistant to the LPP inhibitors, vanadate and propranolol.
溶血磷脂酸（LPA）是一种具有多种生物学功能的信号磷脂，主要通过特定的G蛋白偶联受体介导。异常的LPA信号传导越来越多地与常见人类疾病的病理学相关，如动脉硬化和癌症。LPA信号池的寿命由合成和降解酶活性之间的平衡控制。在本研究中，我们通过药理学方法操纵LPA降解所需的酶机制，对大鼠脑中的这些酶途径进行了表征。
在大鼠脑冰冻切片中，发现生物活性LPA的寿命受脂质磷酸酶（LPPs）的Mg2+非依赖性、N-乙基马来酰亚胺不敏感磷酸酶活性控制。使用功能放射自显影法显示，对这种LPP活性的药理学抑制增强了LPA1受体信号传导。尽管两种LPP抑制剂，原钒酸钠和普萘洛尔，局部增强了受体反应，但正如通过Pi测定和LC/MS/MS所证实的，它们并未影响全脑LPA磷酸酶活性（也归因于Mg2+非依赖性、N-乙基马来酰亚胺不敏感磷酸酶）。有趣的是，磷酸盐类似物氟化铝（AlFx-）不仅不可逆地抑制LPP活性，从而增强LPA1受体反应，而且完全阻止了LPA降解，然而，为了观察AlFx-依赖性的受体信号增强，后一种效应并非必需。
我们得出结论，钒酸盐和普萘洛尔敏感的LPP活性在局部保护LPA信号池，而大多数脑LPA磷酸酶活性归因于LPP样酶活性，该活性与LPP活性一样，对AlFx-敏感，但对LPP抑制剂钒酸盐和普萘洛尔具有抗性。
