Aubin R, Ménard P, Lajeunesse D
Hôpital Maisonneuve-Rosemont, Montréal, Québec, Canada.
Kidney Int. 1996 Nov;50(5):1476-82. doi: 10.1038/ki.1996.461.
Thiazide diuretics have been shown to decrease bone-loss rate and to improve bone mineral density in patients using this medication. However, the exact role of thiazides on bone cells is still debated. In the present work, we studied whether thiazides could affect the normal features of osteoblasts using the human model cell line MG-63. Hydrochlorothiazide (HCTZ) did not affect cell growth nor DNA synthesis in these cells, yet slightly increased alkaline phosphatase activity in these cells at pharmacologically relevant concentrations. Under similar conditions, HCTZ dose-dependently inhibited 1,25(OH)2D3-induced osteocalcin secretion by these cells (maximal effect, -40 to 50%, P < 0.005). However, HCTZ did not inhibit the basal production of osteocalcin in MG-63 cells (without 1,25(OH)2D3 induction), which was very low to undectable. Two different thiazide derivatives, chlorothiazide and cyclothiazide, and two structurally related sulfonamides with selective inhibition of carbonic anhydrase (Acetazolamide) or hyperglycemic effects (Diazoxide) were also tested. Chlorothiazide (1000 microM) inhibited osteocalcin secretion (-42 +/- 12.7%) at doses 10-fold higher than HCTZ (100 microM) while cyclothiazide was effective at doses of 1 microM (-27 +/- 3.6%), and hence 100-fold lower than HCTZ, compatible with the relative natriuretic effect in vivo of these compounds. Acetazolamide (10 microM) poorly affected osteocalcin secretion at doses 100-fold higher than those needed in vivo to inhibit carbonic anhydrase. Likewise, Diazoxide (100 microM) poorly affected osteocalcin secretion at doses known to promote its biological effect. Higher doses of acetazolamide and diazoxide induced cell death. Neither Acetazolamide nor Diazoxide affected alkaline phosphatase, whereas chlorothiazide had a weak positive effect on this enzymatic activity. The production of macrophage colony-stimulating factor (M-CSF) was stimulated in the presence of 1,25(OH)2D3 (50 nM), TNF-alpha (2 ng/ml) or both in MG-63 cells. HCTZ (25 microM, 24 hr of preincubation) did not modify basal M-CSF production and did not reduce the response to 1,25(OH)2D3 alone. In contrast, HCTZ inhibited the response to TNF-alpha alone (P < 0.05), and also reduced the response to a combination of 1,25(OH)2D3 and TNF-alpha (P < 0.01). In conclusion, these results indicate that thiazide diuretics show a selective inhibition of osteocalcin secretion and M-CSF production by MG-63 cells unlike structurally related drugs. Therefore, these features may explain, in part, the positive effect of thiazides on bone mineral density.
噻嗪类利尿剂已被证明可降低使用该药物患者的骨质流失率并提高骨矿物质密度。然而，噻嗪类药物对骨细胞的确切作用仍存在争议。在本研究中，我们使用人源模型细胞系MG-63研究了噻嗪类药物是否会影响成骨细胞的正常特性。氢氯噻嗪（HCTZ）在这些细胞中不影响细胞生长和DNA合成，但在药理学相关浓度下会轻微增加这些细胞中的碱性磷酸酶活性。在类似条件下，HCTZ剂量依赖性地抑制这些细胞中1,25(OH)2D3诱导的骨钙素分泌（最大效应为-40%至50%，P < 0.005）。然而，HCTZ不抑制MG-63细胞中骨钙素的基础分泌（无1,25(OH)2D3诱导），基础分泌水平极低至无法检测。还测试了两种不同的噻嗪类衍生物，氯噻嗪和环噻嗪，以及两种与结构相关的具有选择性抑制碳酸酐酶作用（乙酰唑胺）或降血糖作用（二氮嗪）的磺酰胺。氯噻嗪（1000 microM）在剂量比HCTZ（100 microM）高10倍时抑制骨钙素分泌（-42 +/- 12.7%），而环噻嗪在1 microM剂量时有效（-27 +/- 3.6%），因此比HCTZ低100倍，这与这些化合物在体内的相对利钠作用相符。乙酰唑胺（10 microM）在比体内抑制碳酸酐酶所需剂量高100倍时对骨钙素分泌影响较小。同样，二氮嗪（100 microM）在已知可促进其生物学效应的剂量下对骨钙素分泌影响较小。更高剂量的乙酰唑胺和二氮嗪会诱导细胞死亡。乙酰唑胺和二氮嗪均不影响碱性磷酸酶，而氯噻嗪对该酶活性有微弱的正向作用。在MG-63细胞中，在存在1,25(OH)2D3（50 nM）、TNF-α（2 ng/ml）或两者时，巨噬细胞集落刺激因子（M-CSF）的产生受到刺激。HCTZ（25 microM，预孵育24小时）不改变基础M-CSF产生，也不降低对单独1,25(OH)2D3的反应。相反，HCTZ单独抑制对TNF-α的反应（P < 0.05），也降低对1,25(OH)2D3和TNF-α组合的反应（P < 0.01）。总之，这些结果表明，与结构相关药物不同，噻嗪类利尿剂对MG-63细胞的骨钙素分泌和M-CSF产生具有选择性抑制作用。因此，这些特性可能部分解释了噻嗪类药物对骨矿物质密度的积极作用。
