TLR2 mediates renal apoptosis in neonatal mice subjected experimentally to obstructive nephropathy

Urinary tract obstruction during renal development leads to inflammation, tubular apoptosis, and interstitial fibrosis. Toll like receptors (TLRs) expressed on leukocytes, myofibroblasts and renal cells play a central role in acute inflammation. TLR2 is activated by endogenous danger signals in the kidney; its contribution to renal injury in early life is still a controversial topic. We analyzed TLR2 for a potential role in the neonatal mouse model of congenital obstructive nephropathy. Inborn obstructive nephropathies are a leading cause of end-stage kidney disease in children. Thus, newborn Tlr2-/- and wild type (WT) C57BL/6 mice were subjected to complete unilateral ureteral obstruction (UUO) or sham-operation on the 2nd day of life. The neonatal kidneys were harvested and analyzed at days 7 and 14 of life. Relative expression levels of TLR2, caspase-8, Bcl-2, Bax, GSDMD, GSDME, HMGB1, TNF, galectin-3, α-SMA, MMP-2, and TGF-β proteins were quantified semi-quantitatively by immunoblot analyses. Tubular apoptosis, proliferation, macrophage- and T-cell infiltration, tubular atrophy, and interstitial fibrosis were analyzed immunohistochemically. Neonatal Tlr2-/- mice kidneys exhibited less tubular and interstitial apoptosis as compared to those of WT C57BL/6 mice after UUO. UUO induced neonatally did trigger pyroptosis in kidneys, however to similar degrees in Tlr2-/- and WT mice. Also, tubular atrophy, interstitial fibrosis, tubular proliferation, as well as macrophage and T-cell infiltration were unremarkable. We conclude that while TLR2 mediates apoptosis in the kidneys of neonatal mice subjected to UUO, leukocyte recruitment, interstitial fibrosis, and consequent neonatal obstructive nephropathy might lack a TLR2 involvement.

Phase differences between SCN neurons and their role in photoperiodic encoding; a simulation of ensemble patterns using recorded single unit electrical activity patterns

In mammals, a major circadian pacemaker is located in the suprachiasmatic nuclei (SCN), at the base of the anterior hypothalamus. The pacemaker controls daily rhythms in behavioral, physiological and endocrine functions and is synchronized to the external light-dark cycle via the retinohypothalamic tract. The SCN are also involved in photoperiodic processes. Changes in day-length are perceived by the SCN, and result in a compression or decompression of the SCN ensemble pattern, which appears to be effectuated by changes in phase relationship among oscillating neurons. By simulation experiments, we have previously shown that the duration of the single unit activity pattern is of minor importance for the broadness of the population activity peak. Instead, the phase distribution among neurons is leading to substantial differences in the broadness of the population pattern. We now show that the combination of (i) changes in the single unit activity pattern and (ii) changes in the phase distribution among oscillating neurons is also effective to encode photoperiodic information. Moreover, we simulated the ensemble waveform of the SCN with recently recorded single unit electrical activity patterns of mice under long and short photoperiods. We show that these single unit activity patterns cannot account for changes in the population waveform of the SCN unless their phase distribution is changed. A narrow distribution encodes for short photoperiods, while a wider distribution is required to encode long photoperiods. The present studies show that recorded patterns in single unit activity rhythms, measured under long and short day conditions, can be used in simulation experiments and are informative in showing which attributes of the neuronal discharge patterns leads to the capacity of the SCN to encode photoperiod.