Inositol possesses antifibrotic activity and mitigates pulmonary fibrosis.

BACKGROUND: Myo-inositol (or inositol) and its derivatives not only function as important metabolites for multiple cellular processes but also act as co-factors and second messengers in signaling pathways. Although inositol supplementation has been widely studied in various clinical trials, little is known about its effect on idiopathic pulmonary fibrosis (IPF). Recent studies have demonstrated that IPF lung fibroblasts display arginine dependency due to loss of argininosuccinate synthase 1 (ASS1). However, the metabolic mechanisms underlying ASS1 deficiency and its functional consequence in fibrogenic processes are yet to be elucidated. METHODS: Metabolites extracted from primary lung fibroblasts with different ASS1 status were subjected to untargeted metabolomics analysis. An association of ASS1 deficiency with inositol and its signaling in lung fibroblasts was assessed using molecular biology assays. The therapeutic potential of inositol supplementation in fibroblast phenotypes and lung fibrosis was evaluated in cell-based studies and a bleomycin animal model, respectively. RESULTS: Our metabolomics studies showed that ASS1-deficient lung fibroblasts derived from IPF patients had significantly altered inositol phosphate metabolism. We observed that decreased inositol-4-monophosphate abundance and increased inositol abundance were associated with ASS1 expression in fibroblasts. Furthermore, genetic knockdown of ASS1 expression in primary normal lung fibroblasts led to the activation of inositol-mediated signalosomes, including EGFR and PKC signaling. Treatment with inositol significantly downregulated ASS1 deficiency-mediated signaling pathways and reduced cell invasiveness in IPF lung fibroblasts. Notably, inositol supplementation also mitigated bleomycin-induced fibrotic lesions and collagen deposition in mice. CONCLUSION: These findings taken together demonstrate a novel function of inositol in fibrometabolism and pulmonary fibrosis. Our study provides new evidence for the antifibrotic activity of this metabolite and suggests that inositol supplementation may be a promising therapeutic strategy for IPF.

Identification of the tapetum/microspore-specific promoter of the pathogenesis-related 10 gene and its regulation in the anther of Lilium longiflorum.

A tapetum/microspore-specific pathogenesis-related (PR) 10 gene was previously identified in lily (Lilium longiflorum Thunb.) anthers. In situ hybridization and RNA blot analysis indicated that the lily PR10 genes are expressed specifically and differentially in the tapetum of the anther wall and in microspores during anther development. The accumulation of PR10 transcripts was exogenously induced by gibberellic acid (GA) and was suppressed by ethylene. Studies using inhibitors of GA and ethylene revealed that the lily PR10 is modulated by an antagonistic interaction between GA and ethylene. The treatment of norbornadien, an ethylene inhibitor, caused the tapetum to become densely cytoplasmic and highly polarized, whereas uniconazole, an inhibitor of GA biosynthesis, arrested tapetal development to a status close to that of control. The expression of the lily PR10g promoter in transgenic Arabidopsis was determined using the ß-glucuronidase (GUS) reporter gene indicated that the decisive fragment required for anther specificity is located -1183 bp to -880 bp upstream of the transcription start site. The PR10gPro::barnase transgenic lines exhibited complete male sterility because of the disruption of the tapetum and the deformation of microspore/pollen. The anther specificity of lily PR10 highlights the importance of the tapetum/microspore-specific PR10g promoter for future biotechnological and agricultural applications.

New insights into desiccation-associated gene regulation by Lilium longiflorum ASR during pollen maturation and in transgenic Arabidopsis.

LLA23, a member of the abscisic acid-, stress-, and ripening-induced (ASR) protein family, was previously isolated from lily (Lilium longiflorum) pollen. The lily ASR is induced through desiccation-associated ABA signaling transduction in the pollen. ASRs are highly hydrophilic and intrinsically unstructured proteins with molecular masses generally less than 18 kDa. LLA23 is abundant in the cytoplasm and nuclei of both vegetative and generative cells of pollen grains. The protein in the nucleus and in the cytoplasm is partly regulated by dehydration. A dual role is proposed for LLA23, as a regulator and a protective molecule, upon exposure to water deficits. This chapter reviews the current state of literature on Asr genes, protein structure, function, and their responses to various stresses. In a study, a genome-wide microarray was used to monitor the expression of LLA23-regulated genes, focusing on the relationship between ASR-, glucose-, and drought-inducible genes, and outlined the difference and cross talk of gene expression among these signaling networks. A strong association was observed in the expression of stress-responsive genes and found 25 genes that respond to all three treatments. Highly inducible genes were also found in each specific stress treatment. Promoter sequence analysis of LLA23-inducible genes enabled us not only to identify possible known cis-acting elements in the promoter regions but also to expect the existence of novel cis-acting elements involved in ASR-responsive gene expression. ASR can be used to improve crops and economically important plants against various environmental stresses.

Lily Cdc42/Rac-interactive binding motif-containing protein, a Rop target, involves calcium influx and phosphoproteins during pollen germination and tube growth.

We report unique desiccation-associated ABA signaling transduction through which the Rop (Rho GTPase of plants) and its target LLP12-2 are regulated during the stage of pollen maturation and tube growth. Overexpression of LLP12-2 drastically inhibited pollen germination and tube growth. Studies on the germination inhibitors, Ca (2+) influx blocking agents LaCl 3 and EGTA and an actin-depolymerizing drug, latrunculin B (LatB), revealed that the LLP12-2-induced inhibition of germination and tube growth is significantly suppressed by LaCl 3 and EGTA in the LLP12-2-overexpressing pollen but not by LatB. These results suggested that LLP12-2 is associated with Ca (2+) influx in the cytoplasm and may be not with actin assembly. With the addition of LaCl 3 and EGTA, LLP12-2-overexpressing pollen increased germination and tube growth compared with the one without addition, whereas pollen expressing GFP decreased germination and tube growth. Thus, an optimum level of [Ca (2+) ]cyt influx is crucial for normal germination and tube growth. Studies on the inhibitors, staurosporine and okadaic acid in the LLP12-2-overexpressing pollen, showed no appreciable increase in germination when compared with the one without addition, suggesting that staurosporine-sensitive protein kinases and dephosphorylation of phosphoproteins may be not involved in the LLP12-2 mediated germination. However, the LLP12-2-induced inhibition of tube length was slightly but significantly suppressed by staurosporine, suggesting that staurosporine-sensitive protein kinases involve in the LLP12-2-induced inhibition of tube growth.

Expression and regulation of two novel anther-specific genes in Lilium longiflorum.

Two stage-specific genes have been isolated from a subtractive cDNA library constructed from developing anthers of lily (Lilium longiflorum). The proteins encoded by the two genes have a strong hydrophobic region at the N-terminus, indicating the presence of a signal peptide. The deduced LLA-67 is a new type of small cysteine-rich protein whose sequence exhibits four consecutive CX(3)CX(6-10) repeats that could form signal-receiving finger motifs, while the deduced LLA-115 protein shows significant similarities to a rice unknown protein, and putative cell wall proteins of Medicago truncatula and Arabidopsis. The transcripts of LLA-67 and LLA-115 were anther specific and differentially detected at the phase of microspore development. In situ hybridization with antisense riboprobes of the two genes in the anther showed strong signals localized to the tapetal layer of the anther wall. The LLA-67 mRNA was also detected in the microspore at the phase of microspore development but the LLA-115 mRNA was not. The LLA-115 gene can be exogenously induced by gibberellin (GA), whereas the LLA-67 gene cannot be induced. Studies with the GA biosynthesis inhibitor uniconazole and an inhibitor of ethylene activity, 2,5-norbornadien (NBD), revealed that the two genes were negatively regulated by ethylene and a cross-talk between GA and ethylene was involved in the regulation of the two genes occurring in young anthers. The treatment of NBD caused the tapetum to become densely cytoplasmic and highly polarized, whereas uniconazole arrested tapetal development to a status close to that of control. DNA blots of lily genomic DNA indicated that the two genes were encoded by a small gene family. The different actions of hormones on gene expression and the possible function of the gene products in young anthers are discussed.