Experimental study of the effects of probiotics on Cryptosporidium parvum infection in neonatal rats.

To date, there is no efficient treatment for cryptosporidiosis and parasite eradication relies on innate and acquired immunity. In this study, we investigated the effect of administration of probiotic bacteria on the development and progression of the experimental infection in suckling rats. Rats were fed daily with 2.10(7) CFU of Lactobacillus casei-containing mixture, starting 2 days before the infection until the spontaneous clearance of the parasite. Effects on weight gain, parasite burden, mucosal histology and production of mucosal cytokines (IFNgamma, IL10 and TNFalpha) were studied. Although a trend to a more rapid clearance of parasites was noted in rats treated with probiotics, no significant effect of probiotics administration was observed in terms of weight gain, parasite burden, mucosal damage, or kinetics of mucosal cytokines during the course of infection. Overall, our results showed that the daily administration of L. casei-containing mixtures was unable to eradicate the parasite in our model.

SUT1-promoted sterol uptake involves the ABC transporter Aus1 and the mannoprotein Dan1 whose synergistic action is sufficient for this process.

Efficient sterol influx in the yeast Saccharomyces cerevisiae is restricted to anaerobiosis or to haem deficiency resulting from mutations. Constitutive expression of SUT1, an hypoxic gene encoding a transcriptional regulator, induces sterol uptake in aerobiosis. A genome-wide approach using DNA microarray was used to identify the mediators of SUT1 effects on aerobic sterol uptake. A total of 121 ORFs (open reading frames) were significantly and differentially expressed after SUT1 overexpression, 61 down-regulated and 60 up-regulated. Among these genes, the role of the putative ABC transporter (ATP-binding-cassette transporter) Aus1, and of the cell-wall mannoprotein Dan1, was characterized better. These two genes play an essential role in aerobic sterol uptake, since their deletion compromised the SUT1 effects, but individual overexpression of either of these genes in a wild-type background was not sufficient for this process. However, constitutive co-expression of AUS1 and DAN1 in a wild-type background resulted in sterol influx in aerobiosis. These results suggest that the corresponding proteins may act synergistically in vivo to promote sterol uptake.

Lipid dynamics in yeast under haem-induced unsaturated fatty acid and/or sterol depletion.

In the yeast Saccharomyces cerevisiae, UFA (unsaturated fatty acids) and ergosterol syntheses are aerobic processes that require haem. We took advantage of a strain affected in haem synthesis ( hem1 Delta) to starve specifically for one or the other of these essential lipids in order to examine the consequences on the overall lipid composition. Our results demonstrate that reserve lipids (i.e. triacylglycerols and steryl esters) are depleted independently of haem availability and that their UFA and sterol content is not crucial to sustain residual growth under lipid depletion. In parallel to UFA starvation, a net accumulation of SFA (saturated fatty acids) is observed as a consequence of haem biosynthesis preclusion. Interestingly, the excess SFA are not mainly stored within triacylglycerols and steryl esters but rather within specific phospholipid species, with a marked preference for PtdIns. This results in an increase in the cellular PtdIns content. However, neutral lipid homoeostasis is perturbed under haem starvation. The contribution of two lipid particle-associated proteins (namely Tgl1p and Dga1p) to this process is described.