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Molecular medical research on aromatherapy has been steadily increasing for use as an adjuvant therapy in managing psychiatric disorders and to examine its therapeutic mechanisms. Most studies, as well as clinically applied experience, have indicated that various essential oils, such as lavender, lemon and bergamot can help to relieve stress, anxiety, depression and other mood disorders. Most notably, inhalation of essential oils can communicate signals to the olfactory system and stimulate the brain to exert neurotransmitters (e.g. serotonin and dopamine) thereby further regulating mood. However, little research has been done on the molecular mechanisms underlying these effects, thus their mechanism of action remains ambiguous. Several hypotheses have been proposed regarding the therapeutic mechanism of depression. These have mainly centered on possible deficiencies in monoamines, neurotrophins, the neuroendocrine system, c-AMP, cation channels as well as neuroimmune interactions and epigenetics, however the precise mechanism or mechanisms related to depression have yet to be elucidated. In the current study, the effectiveness of aromatherapy for alleviating psychiatric disorders was examined using data collected from previously published studies and our unpublished data. A possible signaling pathway from olfactory system to the central nerve system and the associated key molecular elements of aromatherapy are also proposed.

Diarrhoeagenic enterohaemorrhagic Escherichia coli and enteropathogenic E. coli attach to human intestinal epithelium and efface brush-border microvilli, forming an A/E (attaching and effacing) lesion. These human pathogens are phenotypically similar to the mouse pathogen Citrobacter rodentium. Genetically, they all have a homologous set of virulent genes involved in the A/E lesion, and these genes are organized on a LEE (locus of enterocyte effacement), a pathogenicity island. This island comprises 41 specific open reading frames, of which most are organized at five operons, LEE1, LEE2, LEE3, LEE4 and tir (LEE5). The expression of the LEE genes is regulated in a complicated manner, and current knowledge is that there are at least two positive regulators, Ler (LEE-encoded regulator) and GrlA (global regulator of LEE activator), and one negative regulator, called GrlR (global regulator of LEE repressor). In enterohaemorrhagic E. coli, GrlA is encoded by l0043, whereas GrlR is encoded by l0044. Here we report a fourth regulatory gene located in LEE3, namely l0036. Its expression is tightly controlled. When overexpressed, this factor, named Mpc (multiple point controller), interacts with Ler and suppresses the expression of the LEE proteins. When the translation is not initiated or terminated before maturation, the type III secretion of effectors is completely abolished. Therefore, together with the fact that several cis elements reside in the region that l0036 spans, l0036 appeared to have multiple functions in the regulation of LEE expression.

Polyphosphate kinase (PPK), the principal enzyme required for the synthesis of inorganic polyphosphate (polyP) from ATP, also exhibits other enzymatic activities, which differ significantly in their biochemical optima and responses to chemical agents. These several activities include: polyP synthesis (forward reaction), nATP → polyPn+ nADP (Equation 1); ATP synthesis from polyP (reverse reaction), ADP + polyPn→ ATP + polyPn − 1(Equation 2); general nucleoside-diphosphate kinase, GDP + polyPn→ GTP + polyPn − 1(Equation 3); linear guanosine 5′-tetraphosphate (ppppG) synthesis, GDP + polyPn→ ppppG + polyPn − 2(Equation4); and autophosphorylation, PPK + ATP → PPK-P + ADP (Equation 5). The Mg2+optima are 5, 2, 1, and 0.2 mm, respectively, for the activities in Equations 1, 2, 3, and 4. Inorganic pyrophosphate inhibits the activities in Equations 1and 3but stimulates that in Equation 4. The kinetics of the activities in Equations 1, 2, and 3are highly processive, whereas the transfer of a pyrophosphoryl group from polyP to GDP (Equation 4) is distributive and demonstrates a rapid equilibrium, random Bi-Bi catalytic mechanism. Radiation target analysis revealed that the principal functional unit of the homotetrameric PPK is a dimer. Exceptions are a trimer for the synthesis of ppppG (Equation 4) and a tetrameric state for the autophosphorylation of PPK (Equation 5) at low ATP concentrations. Thus, the diverse functions of this enzyme involve different subunit organizations and conformations. The highly conserved homology of PPK among 18 microorganisms was used to determine important residues and conserved regions by alanine substitution, by site-directed mutagenesis, and by deletion mutagenesis. Of 46 single-site mutants, seven exhibit none of the five enzymatic activities; in one mutant, ATP synthesis from polyP is reduced relative to GTP synthesis. Among deletion mutants, some lost all five PPK activities, but others retained partial activity for some reactions but not for others.

Treatment of the vacuolar H+ -ATPase from mung bean seedlings (Vigna radiata L.) with the tryptophan modifying agent 2-hydroxyl-5-nitrobenzyl bromide (HNBB), caused a progressive decline of the ATP hydrolysis activity and proton translocation in a time- and concentration-dependent manner. Dithiothreitol could not restore the inhibition of H+ -ATPase by HNBB, indicating possible involvement tryptophan, and not cysteine residues. Protection studies suggested that modified sites might not locate in the active domain. Kinetic analysis shows that Vmax but not Km of H+ -ATPase was changed by HNBB. The reaction order of inactivation by HNBB was calculated as 0.98, implying that at least one tryptophan was labelled. The steady-state dissociation constant (Ki) and the pesudo-first-order rate constant of inhibition (k2) were determined as 1.61 mM and 0.22 min-1, respectively. Furthermore, stoichiometry experiments indicated that 8 mol tryptophan/mol ATPase were modified, when the enzyme activity was completely inhibited. However, a Tsou analysis showed that only one out of these modified tryptophans was crucial to the enzymatic activity. In addition, modification of the vacuolar H+ -ATPase by HNBB led to a decrease in intrinsic fluorescence, suggesting a possible conformational change of the enzyme. Taken together, our data indicate that the tryptophan residue is indispensable to vacuolar H+ -ATPase and the modification of this residue may induce a significant conformational change, consequently resulting in the loss of enzymatic activity. Keywords: vacuole, tonoplast, H+ -ATPase, chemical modification, tryptophan.