Molecular genetic evidence for the place of origin of the Pacific rat, Rattus exulans.

Commensal plants and animals have long been used to track human migrations, with Rattus exulans (the Pacific rat) a common organism for reconstructing Polynesian dispersal in the Pacific. However, with no knowledge of the homeland of R. exulans, the place of origin of this human-commensal relationship is unknown. We conducted a mitochondrial DNA phylogeographic survey of R. exulans diversity across the potential natural range in mainland and Island Southeast Asia in order to establish the origin of this human-commensal dyad. We also conducted allozyme electrophoresis on samples from ISEA to obtain a perspective on patterns of genetic diversity in this critical region. Finally, we compared molecular genetic evidence with knowledge of prehistoric rodent faunas in mainland and ISEA. We find that ISEA populations of R. exulans contain the highest mtDNA lineage diversity including significant haplotype diversity not represented elsewhere in the species range. Within ISEA, the island of Flores in the Lesser Sunda group contains the highest diversity in ISEA (across all loci) and also has a deep fossil record of small mammals that appears to include R. exulans. Therefore, in addition to Flores harboring unusual diversity in the form of Homo floresiensis, dwarfed stegodons and giant rats, this island appears to be the homeland of R. exulans.

Cytotoxic effects of the novel isoflavone, phenoxodiol, on prostate cancer cell lines.

Phenoxodiol is an isoflavone derivative that has been shown to elicit cytotoxic effects against a broad range of human cancers. We examined the effect of phenoxodiol on cell death pathways on the prostate cell lines LNCaP, DU145 and PC3, representative of different stages of prostate cancer, and its effects on cell death pathways in these cell lines. Cell proliferation assays demonstrated a significant reduction in the rate of cell proliferation after 48 h exposure to phenoxodiol (10 and 30 µM). FACS analysis and 3'-end labelling indicated that all three prostate cancer cell lines underwent substantial levels of cell death 48 h after treatment. Mitochondrial membrane depolarization, indicative of early-stage cell death signalling, using JC-1 detection, was also apparent in all cell lines after exposure to phenoxodiol in the absence of caspase-3 activation. Caspase inhibition assays indicated that phenoxodiol operates through a caspase-independent cell death pathway. These data demonstrate that phenoxodiol elicits anti-cancer effects in prostate cancer cell lines representative of early and later stages of development through an as-yet-unknown cell death mechanism. These data warrant the further investigation of phenoxodiol as a potential treatment for prostate cancer.

The expression of tumor necrosis factor-alpha, its receptors and steroidogenic acute regulatory protein during corpus luteum regression.

BACKGROUND: Corpus luteum (CL) regression is known to occur as two parts; functional regression when steroidogenesis declines and structural regression when apoptosis is induced. Previous studies suggest this process occurs by the production of luteolytic factors, such as tumour necrosis factor-alpha (TNF-alpha). METHODS: We examined TNF-alpha, TNF-alpha receptors (TNFR1 and 2) and steroidogenic acute regulatory (StAR) protein expression during CL regression in albino Wistar rats. CL from Days 16 and 22 of pregnancy and Day 3 post-partum were examined, in addition CL from Day 16 of pregnancy were cultured in vitro to induce apoptosis. mRNA was quantitated by kinetic RT-PCR and protein expression examined by immunohistochemistry and Western blot analyses. RESULTS: TNF-alpha mRNA increased on Day 3 post-partum. TNFR were immunolocalized to luteal cells, and an increase in TNFR2 mRNA observed on Day 3 post-partum whilst no change was detected in TNFR1 mRNA relative to Day 16. StAR protein decreased on Day 3 post-partum and following trophic withdrawal but no change was observed following exogenous TNF-alpha treatment. StAR mRNA decreased on Day 3 post-partum; however, it increased following trophic withdrawal and TNF-alpha treatment in vitro. CONCLUSION: These results demonstrate the existence of TNFR1 and TNFR2 in rat CL and suggest the involvement of TNF-alpha in rat CL regression following parturition. Furthermore, decreased StAR expression over the same time points was consistent with the functional regression of the CL.

Cellular mechanisms associated with spontaneous and ciliary neurotrophic factor-cAMP-induced survival and axonal regeneration of adult retinal ganglion cells.

We have shown previously that intraocular elevation of cAMP using the cAMP analog 8-(4-chlorophenylthio)-cAMP (CPT-cAMP) failed to promote axonal regeneration of axotomized adult retinal ganglion cells (RGCs) into peripheral nerve (PN) grafts but significantly potentiated ciliary neurotrophic factor (CNTF)-induced axonal regeneration. Using the PN graft model, we now examine the mechanisms underlying spontaneous and CNTF/CPT-cAMP-induced neuronal survival and axonal regrowth. We found that blockade of the cAMP pathway executor protein kinase A (PKA) using the cell-permeable inhibitor KT5720 did not affect spontaneous survival and axonal regeneration but essentially abolished the CNTF/CPT-cAMP-induced RGC survival and axonal regeneration. Blockade of CNTF signaling pathways such as phosphotidylinositol 3-kinase (PI3K)/akt by 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002), mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) by 2-(2-diamino-3-methoxyphenyl-4H-1-benzopyran-4-one (PD98059), or Janus kinase (JAK)/signal transducer and activators of transcription (STAT3) by tyrphostin AG490 also blocked the CNTF/CPT-cAMP-dependent survival and regeneration effects. PKA activity assay and Western blots showed that KT5720, LY294002, and PD98059 almost completely inhibited PKA, PI3K/akt, and MAPK/ERK signal transduction, respectively, whereas AG490 substantially decreased JAK/STAT3 signal transduction. Intraocular injection of CPT-cAMP resulted in a small PKA-dependent increase in CNTF receptor alpha mRNA expression in the retinas, an effect that may facilitate CNTF action on survival and axonal regeneration. Surprisingly, in the absence of CNTF/CPT-cAMP, LY294002, PD98059, and AG490, but not KT5720, significantly enhanced spontaneous RGC survival, suggesting differential roles of these pathways in RGC survival under different conditions. Our data suggest that CNTF/CPT-cAMP-induced RGC survival and axonal regeneration are a result of multiple pathway actions, with PKA as an essential component, but that these pathways can function in an antagonistic manner under different conditions.

Localization of 11beta-hydroxysteroid dehydrogenase types 1 and 2 in the male reproductive tract.

The action of glucocorticoids in target tissues is dependent on the local expression of glucocorticoid receptors and two 11beta-hydroxysteroid dehydrogenase (11beta-HSD) enzymes, 11beta-HSD1 and 11beta-HSD2, which interconvert active and inactive glucocorticoids. This study examined expression of the 11beta-HSD enzymes in the male reproductive tract of the adult rat. 11beta-HSD1 was immunolocalized to the apical region of principal epithelial cells of the caput epididymis, with the less numerous clear cells devoid of signal. Epididymal 11beta-HSD1 expression was confirmed by Western blot analysis, with immunoreactive species identified at 34 kDa (the expected size for 11beta-HSD1) and at approximately 48 kDa. 11beta-HSD bioactivity was readily detectable in the epididymis, with 11-oxoreductase activity clearly the favored reaction (as observed in liver), consistent with 11beta-HSD1 expression. The epithelium of the vas deferens, seminal vesicle, and penile urethra were also immunopositive for 11beta-HSD1, as were smooth muscle cells of the vas deferens and penile blood vessels. 11beta-HSD2 was also immunolocalized to the epididymal epithelium, but its distribution was complementary to that of 11beta-HSD1 (i.e. clear cells showing intense 11beta-HSD2 staining but principal cells devoid of signal). 11beta-HSD2 was also present in the corpora cavernosa of the penis but not in other tissues. In conclusion, the differential expression of 11beta-HSD1 and 11beta-HSD2 throughout the male reproductive tract suggests that these enzymes locally modulate glucocorticoid and mineralocorticoid actions, particularly in the epididymis and penile vasculature.

Role of tumor necrosis factor-alpha and the modulating effect of the caspases in rat corpus luteum apoptosis.

Tumor necrosis factor-alpha (TNFalpha) is a pleiotropic cytokine that has been implicated in apoptosis of many cell systems. However, the signal transduction of TNFalpha during the structural and functional regression of the corpus luteum (CL) is largely unknown. In this study, we investigate the role of TNFalpha in rat CL apoptosis and the involvement of monocyte chemoattractant protein-1 (MCP-1) and the modulating effect of the caspases in this process. An in vivo study of CL during pregnancy and postpartum using immunohistochemistry and Western blot analysis indicated that increases in TNFalpha correspond with luteal apoptosis approaching term (Day 22) and at postpartum (Day 3). CL apoptosis was further investigated using a whole-CL culture model of tropic withdrawal. An increase was observed in both low molecular weight (MW) DNA fragmentation and TUNEL staining from 0 h to 8 h in culture. CL apoptosis in vitro was associated with increased protein expression of both TNFalpha and MCP-1 as measured by immunohistochemistry and Western blot analysis. Using a whole-CL culture model, apoptosis was induced in vitro by TNFalpha as demonstrated by a dose-dependent increase in DNA fragmentation. Treatment of luteal cells with TNFalpha and both specific caspase inhibitors (Z-DEVD-FMK, Z-VEID-FMK, Z-IETD-FMK) or a general caspase inhibitor (Boc-D-FMK) prevented the effect of TNFalpha. CL regression involves the apoptotic deletion of luteal cells; the results of this study suggest that TNFalpha is possibly involved in this process. The observed increases in MCP-1 expression suggest the coordination of TNFalpha expression with the infiltration and activation of macrophages. Furthermore, the results demonstrate the importance of the caspases in the TNFalpha signal transduction pathway and suggest a hierarchy within the caspase family.