No abstract

In muscular dystrophies (MD) the loss of muscle and its ability to function are associated with fibrosis. We evaluated the efficacy of halofuginone in reducing fibrosis in the dy(2J)/dy(2J) mouse model of congenital MD. Mice were injected intraperitoneally with 5 microg of halofuginone 3 times a week for 5 or 15 weeks, starting at the age of 3 weeks. Halofuginone caused a reduction in collagen synthesis in hindlimb muscles. This was associated with reductions in the degenerated area, in cell proliferation, in the number of myofibers with central nuclei, with increased myofiber diameter, and with enhanced motor coordination and balance. Halofuginone caused a reduction in infiltrating fibroblasts that were located close to centrally nucleated myofibers. Our results suggest that halofuginone reduced the deleterious effects of fibrosis, thus improving muscle integrity. Halofuginone meets the criteria for a novel antifibrotic therapy for MD patients.

Rhizopus delemar and associated species attack a wide range of fruit and vegetables after harvest. Host nutrients and acidic pH are required for optimal germination of R. delemar, and we studied how this process is triggered. Glucose induced spore swelling in an acidic environment, expressed by an up to 3-fold increase in spore diameter, whereas spore diameter was smaller in a neutral environment. When suspended in an acidic environment, the spores started to float, indicating a change in their density. Treatment of the spores with HgCl2, an aquaporin blocker, prevented floating and inhibited spore swelling and germ-tube emergence, indicating the importance of water uptake at the early stages of germination. Two putative candidate aquaporin-encoding genes—RdAQP1 and RdAQP2—were identified in the R. delemar genome. Both presented the conserved NPA motif and six-transmembrane domain topology. Expressing RdAQP1 and RdAQP2 in Arabidopsis protoplasts increased the cells' osmotic water permeability coefficient (Pf) compared to controls, indicating their role as water channels. A decrease in R. delemar aquaporin activity with increasing external pH suggested pH regulation of these proteins. Substitution of two histidine (His) residues, positioned on two loops facing the outer side of the cell, with alanine eliminated the pH sensing resulting in similar Pf values under acidic and basic conditions. Since hydration is critical for spore switching from the resting to activate state, we suggest that pH regulation of the aquaporins can regulate the initial phase of R. delemar spore germination, followed by germ-tube elongation and host-tissue infection.