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氢气的生物学效应在2007年被日本学者发现,启动了氢气生物学效应研究的热潮,到目前已经有将近200篇临床和基础研究论文问世,并且促进大量氢气的相关产品进入市场,也给将来氢气的临床应用带来了无限遐想。两年前本人根据一篇关于甲烷生物学作用的综述,提出“甲烷:新的生物活性气体”的初步想法。但该想法并没有继续,也没有进行任何试验。最近CCM上的一篇文章证明呼吸少量甲烷可以治疗小肠缺血引起的炎症反应,这应该是一个非常重要的发现。
作为一种经典的生物学气体分子,甲烷早就为生物学领域的人们熟悉,甲烷是最常见的细菌代谢产物,也有人证明植物和动物细胞具备产生甲烷的能力,由于在人类和动物大肠细菌具有产生甲烷的能力,曾经有人提出甲烷可能对肠道功能产生影响。但更多的观点认为甲烷属于相对惰性的气体,只有在高浓度情况下具有一定麻醉作用,没有人意识到小剂量甲烷在抗炎症抗氧化损伤中的作用。尽管我在两年前曾经提出甲烷可能具有更多生物学效应,但并没有考虑到其抗氧化作用。记得当时曾查过甲烷的还原性,甲烷的碳氢键能413kJ/mol和氢气的氢键436kJ/mol非常接近,当时我曾经想,为什么氢气具有那么好的抗氧化损伤效应,而甲烷没有这个作用?甚至考虑用甲烷作为阴性对照来证明氢气的特殊作用。看来这个前提就是错误的,为什么当时没有这样想:既然两个气体的键能如此接近,甲烷也应该具有类似的作用。
这个文章虽然发表在普通的Crit Care Med杂志上,不象氢气的第一篇论文发表在《自然医学》这样的能吸引眼球的杂志上,但我认为这个发现(如果是正确的话)的意义一点也不亚于发现氢气效应的地位。而且由于甲烷的自身特点,决定了甲烷作为医学气体将具有重要地位。首先,从气体的性质上考虑,甲烷具有更理想特性用来研究。例如,甲烷可能是内源性气体,在缺氧的情况下,动物血管内皮细胞具有产生甲烷的能力。那么在一些缺血性疾病就有可能产生一定水平的甲烷。其次,甲烷是脂溶性气体,比较容易制备出临床使用的制剂。可以用酒精等有机溶剂制备生物溶液制剂,这要比氢气难以溶解的特点要优越地多。另外甲烷可以和水结合成水合甲烷,这也可以作为一种运输、储存和使用甲烷的方式。最后,甲烷气体分子量相对比较大,不容易从容器中泄露,在开发相关药物和保健品方面更方便更安全。这些特点将注定比氢气具有更广阔的应用前景。
甲烷抗氧化效应的发现,对氢气的研究来讲有利有弊。有利的方面是,这是一个在物理化学性质上和氢气接近的气体,可以在将来的研究中和氢气作为一类气体分子,部分研究结果可以用来解释氢气的效应。对壮大这类气体生物学效应研究的整体影响力显然有好处。不利的方面是,氢气的学术地位将会受到挑战。从整体上考虑,甲烷抗氧化效应的发现对氢气的研究应该是利大于弊。
该研究是来自匈牙利塞格德大学外科研究所的学者 Boros(第一和通讯作者),研究中他们先用大鼠连续呼吸2.5%的甲烷空气混合气体4小时,除发现对缺氧引起的炎症反应有治疗作用外,对动物的基本生理指标没有明显影响。说明甲烷呼吸是非常安全的。然后他们用犬做小肠缺血再灌注模型(为什么不用大鼠),在缺血结束前5分钟开始呼吸2.5%的甲烷15分钟。结果发现对小肠缺血再灌注损伤具有非常强大的治疗作用,例如可以使血液中二氧化碳分压显著降低(因为血液中NO升高,他们推测是甲烷降低了血管阻力,难道甲烷的扩张血管能力比二氧化碳厉害),对缺血小肠局部的超氧阴离子、硝基酪氨酸、MPO、黄嘌呤氧化还原酶增加等都有明显的抑制作用。对小肠缺血组织的形态学观察也证明能显著改善(从2.7降低到1.6)。体外粒细胞研究证明对超氧阴离子和黄嘌呤氧化还原酶的降低作用具有剂量依赖性。
全文:The anti-inflammatory effects of methane.pdf
同期有来自加州大学洛杉矶分校的评论
相关文献,高等生物产生甲烷的证据
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Crit Care Med. 2012 Apr;40(4):1269-1278.
The anti-inflammatory effects of methane*Boros M, Ghyczy M, Erces D, Varga G, Tőkés T, Kupai K, Torday C, Kaszaki J.
SourceFrom the Institute of Surgical Research, Department of Biochemistry, University of Szeged, Szeged, Hungary.
Abstract OBJECTIVE:Gastrointestinal methane generation has been demonstrated in various stress conditions, but it is not known whether nonasphyxiating amounts have any impact on the mammalian pathophysiology. We set out to characterize the effects of exogenous methane administration on the process of inflammatory events arising after reoxygenation in a large animal model of ischemia-reperfusion.
DESIGN:A randomized, controlled in vivo animal study.
SETTING:A university research laboratory.
SUBJECTS:Inbred beagle dogs (12.7 6 2 kg).
INTERVENTIONS:Sodium pentobarbital-anesthetized animals were randomly assigned to sham-operated or ischemia-reperfusion groups, where superior mesenteric artery occlusion was maintained for 1 hr and the subsequent reperfusion was monitored for 3 hrs. For 5 mins before reperfusion, the animals were mechanically ventilated with normoxic artificial air with or without 2.5% methane. Biological responses to methane-oxygen respirations were defined in pilot rat studies and assay systems were used with xanthine oxidase and activated canine granulocytes to test the in vitro bioactivity potential of different gas concentrations.
MEASUREMENTS AND MAIN RESULTS:The macrohemodynamics and small intestinal pCO2 gap changes were recorded and peripheral blood samples were taken for plasma nitrite/nitrate and myeloperoxidase analyses. Tissue superoxide and nitrotyrosine levels and myeloperoxidase activity changes were determined in intestinal biopsy samples; structural mucosal damage was measured by hematoxylin and eosin staining. Methane inhalation did not influence the macrohemodynamics but significantly reduced the magnitude of the tissue damage and the intestinal pCO2 gap changes after reperfusion. Furthermore, the plasma and mucosal myeloperoxidase activity and the intestinal superoxide and nitrotyrosine levels were reduced, whereas the plasma nitrite/nitrate concentrations were increased. Additionally, methane effectively and specifically inhibited leukocyte activation in vitro.
CONCLUSIONS:These data demonstrate the anti-inflammatory profile of methane. The study provides evidence that exogenous methane modulates leukocyte activation and affects key events of ischemia-reperfusion-induced oxidative and nitrosative stress and is therefore of potential therapeutic interest in inflammatory pathologies. (Crit Care Med 2012; 40:-1278).
常见化学键的键长与键能
http://baike.baidu.com/view/323971.htm
[1] 常见化学键的键长与键能 Bond Lengths and Bond Energies of Commonly Chemical Bonds
化 学 键(Chemical bond) | 键 长 (Bond length) /(10-12m) |
键 能 (Bond energy) /(kJ/mol) |
化 学 键(Chemical bond) | 键 长 (Bond length) /(10-12m) |
键 能 (Bond energy) /(kJ/mol) |
B—F | - | 644 | N—H | 101 | 389 |
B—O | - | 515 | N—N | 145 | 159 |
Br—Br | 229 | 193 | N═N | 125 | 456 |
C—B | 156 | 393 | N≡N | 110 | 946 |
C—Br | 194 | 276 | N—O | 146 | 230 |
C—C | 154 | 332 | N═O | 114 | 607 |
C═C | 134 | 611 | Na—Br | 250 | 367 |
C≡C | 120 | 837 | Na—Cl | 236 | 412 |
C—Cl | 177 | 328 | Na—F | 193 | 519 |
C—F | 138 | 485 | Na—H | 189 | 186 |
C—H | 109 | 414 | Na—I | 271 | 304 |
C—I | 214 | 240 | O—H | 98 | 464 |
C—N | 148 | 305 | O—O | 148 | 146 |
C═N | 135 | 615 | O═O | 120 | 498 |
C≡N | 116 | 891 | P—Br | 220 | 272 |
C—O | 143 | 326 | P—Cl | 203 | 331 |
C═O | 120 | 728 | P—H | 142 | 322 |
C═O(CO2) | - | 803 | P—O | 163 | 410 |
C—P | 187 | 305 | P═O | 138 | 585 |
C—S | 182 | 272 | P—P | - | 213 |
C═S | 156 | 536 | Pb—O | 192 | 382 |
C═S(CS2) | - | 577 | Pb—S | 239 | 346 |
C—Si | 186 | 347 | Rb—Br | 294 | 381 |
Cl—Cl | 199 | 243 | Rb—Cl | 279 | 428 |
Cs—I | 337 | 337 | Rb—F | 227 | 494 |
F—F | 140 | 153 | Rb—I | 318 | 319 |
H—H | 75 | 436 | S—H | 135 | 339 |
H—Br | 142 | 366 | S—O | - | 364 |
H—Cl | 127 | 431 | S═O | 143 | - |
H—F | 92 | 565 | S—S | 207 | 268 |
H—I | 161 | 298 | S═S | 189 | - |
I—I | 266 | 151 | Se—H | 147 | 314 |
K—Br | 282 | 380 | Se—Se | 232 | - |
K—Cl | 267 | 433 | Se═Se | 215 | - |
K—F | 217 | 498 | Si—Cl | - | 360 |
K—I | 305 | 325 | Si—F | - | 552 |
Li—Cl | 202 | 469 | Si—H | - | 377 |
Li—H | 239 | 238 | Si—O | - | 460 |
Li—I | 238 | 345 | Si—Si | - | 176 |
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