T-kininogen can either induce or inhibit proliferation in Balb/c 3T3 fibroblasts, depending on the route of administration

Transcriptome temporal and functional analysis of liver regeneration termination

Decades of liver regeneration studies still left the termination phase least elucidated. However regeneration ending mechanisms are clinicaly relevant. We aimed to analyse the timing and transcriptional control of the latest phase of liver regeneration, both controversial. Male Wistar rats were subjected to 2/3 partial hepatectomy with recovery lasting from 1 to 14 days. Time-series microarray data were assessed by innovative combination of hierarchical clustering and principal component analysis and validated by real-time RT-PCR. Hierarchical clustering and principal component analysis in agreement distinguished three temporal phases of liver regeneration. We found 359 genes specifically altered during late phase regeneration. Gene enrichment analysis and manual review of microarray data suggested five pathways worth further study: PPAR signalling pathway; lipid metabolism; complement, coagulation and fibrinolytic cascades; ECM remodelling and xenobiotic biotransformation. Microarray findings pertinent for termination phase were substantiated by real-time RT-PCR. In conclusion, transcriptional profiling mapped late phase of liver regeneration beyond 5(th) day of recovery and revealed 5 pathways specifically acting at this time. Inclusion of longer post-surgery intervals brought improved coverage of regeneration time dynamics and is advisable for further works. Investigation into the workings of suggested pathways might prove helpful in preventing and managing liver tumours.

Kininogens: More than cysteine protease inhibitors and kinin precursors

Two kininogens are found in mammalian sera: HK (high molecular weight kininogen) and LK (low molecular weight kininogen) with the exception of the rat which encompasses a third kininogen, T-Kininogen (TK). Kininogens are multifunctional glycosylated molecules related to cystatins (clan IH, family I25). They harbor three cystatin domains but only two of them are tight-binding inhibitors of cysteine cathepsins. HK and LK, but not TK, are precursors of potent peptide hormones, the kinins, which are released proteolytically by tissue and plasma kallikreins. Besides these classical features novel functions of kininogens have been recently discovered; they are described in the second part of this review. HKa, which corresponds to the kinin-free two-chain HK and its isolated domain D5 (kininostatin), possesses angiostatic and pro-apoptotic properties, inhibits the proliferation of endothelial cells and participates in the regulation of angiogenesis. Moreover, some HK-derived peptides display potent and broad-spectrum microbicidal properties against both Gram-positive and Gram-negative bacteria, and thus may offer a promising alternative to conventional antibiotic therapy. Of seminal interest, a kininogen-derived peptide inhibits activation of the contact phase system of coagulation and protects mice with invasive Streptococcus pyogenes infection from pulmonary lesions. On the other hand, TK is a biomarker of aging at the end of lifespan of elderly rats. However, although TK has been initially identified as an acute phase reactant, and earlier known as alpha-l-acute phase globulin, the increase of TK in liver and plasma is not known to relate to any inflammatory event during the senescence process.

T-kininogen: a biomarker of aging in Fisher 344 rats with possible implications for the immune response

T-kininogen (T-KG) is a reliable biomarker of aging in male Sprague-Dawley rats. Here we confirm, in a longitudinal study, a similar behavior in Fisher 344 rats of both sexes. In males, the increase in serum levels of T-KG follows an exponential curve, whereas in females the increase is best fitted by a linear curve. In both genders, dietary restriction delays the increase in T-KG. We have previously shown that T-KG inhibits T lymphocyte proliferation. Here we show that serum T-KG levels correlate negatively with the ability of splenocytes (most likely B cells) to proliferate in response to lipopolysaccharide. A similar correlation was not observed with other markers of inflammation, including alpha1-acid glycoprotein (AGP), haptoglobin, or interleukin-10. We conclude that the increase in serum T-KG represents a useful biomarker of aging in Fisher 344, and it correlates with decreased lymphocyte proliferation with age, although a cause-effect relationship has not been established.

T-kininogen, a cystatin-like molecule, inhibits ERK-dependent lymphocyte proliferation

Plasma levels of kininogens increase with age in both rats and humans. Kininogens are inhibitors of cysteine proteinases, and filarial cysteine proteinase inhibitors (cystatins) reduce the proliferation of T cells. We evaluated whether T-kininogen (T-KG) might mimic this effect, and here we present data indicating that exposure of either rat splenocytes or Jurkat cells to purified T-KG results in inhibition of both ERK activation and [(3)H]-thymidine incorporation, both basal and in response to ConA or PHA. Interestingly, T-KG did not impair [(3)H]-thymidine incorporation in response to IL-2, which requires primarily the activation of the JNK and Jak/STAT pathways. These effects were neither the consequence of increased cell death, nor required the activity of kinin receptors. Furthermore, when T cell receptor proximal events were bypassed by the use of PMA plus Calcium ionophore, T-KG no longer inhibited ERK activation, suggesting that inhibition occurs upstream of these events, possibly at the level of membrane associated signal transduction molecules. We conclude that, like filarial cystatins, T-KG inhibits ERK-dependent T cell proliferation, and these observations suggest a possible role for T-KG in immunosenescence.