Plasma metabonomic study on the effect of Para‑hydroxybenzaldehyde intervention in a rat model of transient focal cerebral ischemia

Gastrodia elata Blume has been widely used to treat various central and peripheral nerve diseases, and Para-hydroxybenzaldehyde (PHBA) is one of the indicated components suggested to provide a neuroprotective effect. In our previous, it was shown that PHBA protected mitochondria against cerebral ischemia-reperfusion (I/R) injury in rats. In the present study, how PHBA regulated the metabolic mechanism in blood following cerebral I/R was assessed to identify an effective therapeutic target for the prevention and treatment of ischemic stroke (IS). First, a rat model of cerebral ischemia-reperfusion injury was established via middle cerebral artery occlusion/reperfusion (MCAO/R). The therapeutic effect of PHBA on brain I/R was evaluated by assessing the neurological function score, triphenyl tetrazolium chloride, hematoxylin and eosin, and Nissl staining. Next, a non-targeted metabolomic based on high-performance liquid chromatography quadrupole time-of-flight mass spectrometry was established to identify differential metabolites. Finally, a targeted metabolic spectrum was analyzed and the potential therapeutic targets were verified by Western blotting. The results showed that the neurological function score, cerebral infarction area, hippocampal morphology, and the number of neurons in the PHBA group were significantly improved compared with the model group. Metabonomic analysis showed that 13 different metabolites were identified between the model and PHBA group, which may be involved in the ‘tricarboxylic acid cycle’, ‘glutathione metabolism’, and ‘mutual transformation of pentose and glucuronates’, amongst others. Among these, the levels of the most significant differential metabolite, dGMP, decreased significantly following PHBA treatment. Western blotting was used to verify the expression of membrane-associated guanosine kinase PSD-95 and the subunit of glutamate AMPA receptor GluA1, which significantly increased after PHBA treatment. In addition, it was also found that PHBA increased the expression of the light chain-3 protein and autophagy effector protein 1, whilst the expression of sequestosome-1 decreased, indicating that PHBA promoted autophagy. Similarly, in TUNEL staining and detection of apoptosis-related proteins, it was found that MCAO/R upregulated the expression of Bax and cleaved-caspase-3 whilst downregulating the expression of Bcl-2 and increasing the apoptosis of hippocampal neurons; PHBA reversed this situation. These results suggest that cerebral I/R causes postsynaptic dysfunction by disrupting the interaction between PSD-95 and AMPARs, and the inhibition of the autophagy system eventually leads to the apoptosis of hippocampal neurons.