Di Gregorio Elisabetta, Staelens Michael, Hosseinkhah Nazanin, Karimpoor Mahroo, Liburd Janine, Lim Lew, Shankar Karthik, Tuszyński Jack A
Department of Physics, Faculty of Science, University of Alberta, Edmonton, AB T6G 2E1, Canada.
Department of Mechanical and Aerospace Engineering (DIMEAS), Faculty of Biomedical Engineering, Polytechnic University of Turin, 10129 Turin, Italy.
Nanomaterials (Basel). 2024 Jun 26;14(13):1093. doi: 10.3390/nano14131093.
In small clinical studies, the application of transcranial photobiomodulation (PBM), which typically delivers low-intensity near-infrared (NIR) to treat the brain, has led to some remarkable results in the treatment of dementia and several neurodegenerative diseases. However, despite the extensive literature detailing the mechanisms of action underlying PBM outcomes, the specific mechanisms affecting neurodegenerative diseases are not entirely clear. While large clinical trials are warranted to validate these findings, evidence of the mechanisms can explain and thus provide credible support for PBM as a potential treatment for these diseases. Tubulin and its polymerized state of microtubules have been known to play important roles in the pathology of Alzheimer's and other neurodegenerative diseases. Thus, we investigated the effects of PBM on these cellular structures in the quest for insights into the underlying therapeutic mechanisms. In this study, we employed a Raman spectroscopic analysis of the amide I band of polymerized samples of tubulin exposed to pulsed low-intensity NIR radiation (810 nm, 10 Hz, 22.5 J/cm dose). Peaks in the Raman fingerprint region (300-1900 cm)-in particular, in the amide I band (1600-1700 cm)-were used to quantify the percentage of protein secondary structures. Under this band, hidden signals of C=O stretching, belonging to different structures, are superimposed, producing a complex signal as a result. An accurate decomposition of the amide I band is therefore required for the reliable analysis of the conformation of proteins, which we achieved through a straightforward method employing a Voigt profile. This approach was validated through secondary structure analyses of unexposed control samples, for which comparisons with other values available in the literature could be conducted. Subsequently, using this validated method, we present novel findings of statistically significant alterations in the secondary structures of polymerized NIR-exposed tubulin, characterized by a notable decrease in α-helix content and a concurrent increase in β-sheets compared to the control samples. This PBM-induced α-helix to β-sheet transition connects to reduced microtubule stability and the introduction of dynamism to allow for the remodeling and, consequently, refreshing of microtubule structures. This newly discovered mechanism could have implications for reducing the risks associated with brain aging, including neurodegenerative diseases like Alzheimer's disease, through the introduction of an intervention following this transition.
在小型临床研究中，经颅光生物调节（PBM）的应用通常是通过传递低强度近红外光（NIR）来治疗大脑，在痴呆症和几种神经退行性疾病的治疗中取得了一些显著成果。然而，尽管有大量文献详细阐述了PBM疗效背后的作用机制，但影响神经退行性疾病的具体机制仍不完全清楚。虽然需要进行大规模临床试验来验证这些发现，但机制方面的证据可以解释并因此为PBM作为这些疾病的潜在治疗方法提供可靠支持。已知微管蛋白及其聚合状态的微管在阿尔茨海默病和其他神经退行性疾病的病理过程中发挥重要作用。因此，我们研究了PBM对这些细胞结构的影响，以深入了解其潜在的治疗机制。在本研究中，我们对暴露于脉冲低强度近红外辐射（810 nm，10 Hz，22.5 J/cm剂量）的微管蛋白聚合样品的酰胺I带进行了拉曼光谱分析。拉曼指纹区（300 - 1900 cm）的峰，特别是酰胺I带（1600 - 1700 cm）的峰，用于量化蛋白质二级结构的百分比。在该波段下，属于不同结构的C = O拉伸隐藏信号相互叠加，产生复杂信号。因此，为了可靠地分析蛋白质构象，需要对酰胺I带进行准确分解，我们通过采用Voigt轮廓的直接方法实现了这一点。通过对未暴露对照样品的二级结构分析验证了该方法，可将其与文献中其他可用值进行比较。随后，使用这种经过验证的方法，我们展示了新的发现，即暴露于近红外光的聚合微管蛋白二级结构发生了具有统计学意义的显著变化，其特征是与对照样品相比，α - 螺旋含量显著降低，β - 折叠同时增加。这种由PBM诱导的α - 螺旋向β - 折叠的转变与微管稳定性降低以及引入动态性有关，从而允许微管结构的重塑并因此焕然一新。这一新发现的机制可能通过在这种转变后引入干预措施，对降低与脑老化相关的风险产生影响，包括像阿尔茨海默病这样的神经退行性疾病。
