Molecular characterization of chronic cutaneous wounds reveals subregion- and wound type-specific differential gene expression

A limited understanding of the pathology underlying chronic wounds has hindered the development of effective diagnostic markers and pharmaceutical interventions. This study aimed to elucidate the molecular composition of various common chronic ulcer types to facilitate drug discovery strategies. We conducted a comprehensive analysis of leg ulcers (LUs), encompassing venous and arterial ulcers, foot ulcers (FUs), pressure ulcers (PUs), and compared them with surgical wound healing complications (WHCs). To explore the pathophysiological mechanisms and identify similarities or differences within wounds, we dissected wounds into distinct subregions, including the wound bed, border, and peri-wound areas, and compared them against intact skin. By correlating histopathology, RNA sequencing (RNA-Seq), and immunohistochemistry (IHC), we identified unique genes, pathways, and cell type abundance patterns in each wound type and subregion. These correlations aim to aid clinicians in selecting targeted treatment options and informing the design of future preclinical and clinical studies in wound healing. Notably, specific genes, such as PITX1 and UPP1, exhibited exclusive upregulation in LUs and FUs, potentially offering significant benefits to specialists in limb preservation and clinical treatment decisions. In contrast, comparisons between different wound subregions, regardless of wound type, revealed distinct expression profiles. The pleiotropic chemokine-like ligand GPR15L (C10orf99) and transmembrane serine proteases TMPRSS11A/D were significantly upregulated in wound border subregions. Interestingly, WHCs exhibited a nearly identical transcriptome to PUs, indicating clinical relevance. Histological examination revealed blood vessel occlusions with impaired angiogenesis in chronic wounds, alongside elevated expression of genes and immunoreactive markers related to blood vessel and lymphatic epithelial cells in wound bed subregions. Additionally, inflammatory and epithelial markers indicated heightened inflammatory responses in wound bed and border subregions and reduced wound bed epithelialization. In summary, chronic wounds from diverse anatomical sites share common aspects of wound pathophysiology but also exhibit distinct molecular differences. These unique molecular characteristics present promising opportunities for drug discovery and treatment, particularly for patients suffering from chronic wounds. The identified diagnostic markers hold the potential to enhance preclinical and clinical trials in the field of wound healing.

Biomarker-Based Classification and Localization of Renal Lesions Using Learned Representations of Histology-A Machine Learning Approach to Histopathology

Several deep learning approaches have been proposed to address the challenges in computational pathology by learning structural details in an unbiased way. Transfer learning allows starting from a learned representation of a pretrained model to be directly used or fine-tuned for a new domain. However, in histopathology, the problem domain is tissue-specific and putting together a labelled data set is challenging. On the other hand, whole slide-level annotations, such as biomarker levels, are much easier to obtain. We compare two pretrained models, one histology-specific and one from ImageNet on various computational pathology tasks. We show that a domain-specific model (HistoNet) contains richer information for biomarker classification, localization of biomarker-relevant morphology within a slide, and the prediction of expert-graded features. We use a weakly supervised approach to discriminate slides based on biomarker level and simultaneously predict which regions contribute to that prediction. We employ multitask learning to show that learned representations correlate with morphological features graded by expert pathologists. All of these results are demonstrated in the context of renal toxicity in a mechanistic study of compound toxicity in rat models. Our results emphasize the importance of histology-specific models and their knowledge representations for solving a wide range of computational pathology tasks.

Imaging Mass Cytometry and Single-Cell Genomics Reveal Differential Depletion and Repletion of B-Cell Populations Following Ofatumumab Treatment in Cynomolgus Monkeys

Ofatumumab is the first, fully human, anti-CD20 monoclonal antibody in Phase 3 development for multiple sclerosis (MS). The study focused on changes in lymphocyte subsets in blood and lymphoid tissues and on potential novel biomarkers as a result of anti-CD20 antibody action in Cynomolgus monkeys treated with human equivalent doses of subcutaneous (s.c.) ofatumumab on Days 0, 7, and 14. Axillary lymph nodes (LNs) and blood samples were collected at various time points until Day 90. Lymphocyte subsets were quantified by flow cytometry, while morphological and immune cell changes were assessed by imaging mass cytometry (IMC), immunohistochemistry (IHC), in situ hybridization (ISH), and transcriptome analyses using single-cell methodology. Ofatumumab treatment resulted in a potent and rapid reduction of B cells along with a simultaneous drop in CD20⁺ T cell counts. At Day 21, IHC revealed B-cell depletion in the perifollicular and interfollicular area of axillary LNs, while only the core of the germinal center was depleted of CD20⁺CD21⁺ cells. By Day 62, the perifollicular and interfollicular areas were abundantly infiltrated by CD21⁺ B cells and this distribution returned to the baseline cytoarchitecture by Day 90. By IMC CD20⁺CD3⁺CD8⁺ cells could be identified at the margin of the follicles, with a similar pattern of distribution at Day 21 and 90. Single-cell transcriptomics analysis showed that ofatumumab induced reversible changes in t-distributed stochastic neighbor embedding (t-SNE) defined B-cell subsets that may serve as biomarkers for drug action. In summary, low dose s.c. ofatumumab potently depletes both B cells and CD20⁺ T cells but apparently spares marginal zone (MZ) B cells in the spleen and LN. These findings add to our molecular and tissue-architectural understanding of ofatumumab treatment effects on B-cell subsets.

The BACE-1 inhibitor CNP520 for prevention trials in Alzheimer's disease

The beta‐site amyloid precursor protein cleaving enzyme‐1 (BACE‐1) initiates the generation of amyloid‐β (Aβ), and the amyloid cascade leading to amyloid plaque deposition, neurodegeneration, and dementia in Alzheimer's disease (AD). Clinical failures of anti‐Aβ therapies in dementia stages suggest that treatment has to start in the early, asymptomatic disease states. The BACE‐1 inhibitor CNP520 has a selectivity, pharmacodynamics, and distribution profile suitable for AD prevention studies. CNP520 reduced brain and cerebrospinal fluid (CSF) Aβ in rats and dogs, and Aβ plaque deposition in APP‐transgenic mice. Animal toxicology studies of CNP520 demonstrated sufficient safety margins, with no signs of hair depigmentation, retina degeneration, liver toxicity, or cardiovascular effects. In healthy adults ≥ 60 years old, treatment with CNP520 was safe and well tolerated and resulted in robust and dose‐dependent Aβ reduction in the cerebrospinal fluid. Thus, long‐term, pivotal studies with CNP520 have been initiated in the Generation Program.

Editor's Highlight: Comparative Renal Safety Assessment of the Hepatitis B Drugs, Adefovir, Tenofovir, Telbivudine and Entecavir in Rats

The aim of this study was to determine the relative safety of 4 antiviral drugs (telbivudine, tenofovir, adefovir, and entecavir) against hepatitis B virus with respect to kidney function and toxicity in male Sprague Dawley rats. The antiviral drugs were administered once daily for 4 weeks by oral gavage at ∼10 and 25-40 times the human equivalent dose. Main assessments included markers of renal toxicity in urine, magnetic resonance imaging (MRI) of kidney function, histopathology, and electron microscopic examination. Administration of adefovir at 11 and 28 mg/kg for 4 weeks caused functional and morphological kidney alterations in a time- and dose-dependent manner, affecting mainly the proximal tubules and suggesting a mechanism of toxicity related to mitochondrial degeneration/depletion. Of note, the observed adefovir-induced reduction of kidney function was not detected by the standard method of glomerular filtration rate (GFR) measurements (clearance rate of the endogenous marker, creatinine), thereby emphasizing the superiority of MRI in terms of sensitive detection of GFR in rats. For the low dose of 300 mg/kg of tenofovir, minor kidney effects such as nuclear enlargement in the tubular epithelium, and hyaline droplets accumulation were detected, which was also observed for the low dose (11 mg/kg) of adefovir. No assessments could be done at the higher dose of 600/1000 mg/kg tenofovir due to gastrointestinal tract toxicity which prevented treatment of the animals for longer than 1 week. Entecavir at 1 and 3 mg/kg and telbivudine at 600 and 1600 mg/kg caused no toxicologically relevant effects on the kidney.

Phenobarbital induces cell cycle transcriptional responses in mouse liver humanized for constitutive androstane and pregnane x receptors

The constitutive androstane receptor (CAR) and the pregnane X receptor (PXR) are closely related nuclear receptors involved in drug metabolism and play important roles in the mechanism of phenobarbital (PB)-induced rodent nongenotoxic hepatocarcinogenesis. Here, we have used a humanized CAR/PXR mouse model to examine potential species differences in receptor-dependent mechanisms underlying liver tissue molecular responses to PB. Early and late transcriptomic responses to sustained PB exposure were investigated in liver tissue from double knock-out CAR and PXR (CAR(KO)-PXR(KO)), double humanized CAR and PXR (CAR(h)-PXR(h)), and wild-type C57BL/6 mice. Wild-type and CAR(h)-PXR(h) mouse livers exhibited temporally and quantitatively similar transcriptional responses during 91 days of PB exposure including the sustained induction of the xenobiotic response gene Cyp2b10, the Wnt signaling inhibitor Wisp1, and noncoding RNA biomarkers from the Dlk1-Dio3 locus. Transient induction of DNA replication (Hells, Mcm6, and Esco2) and mitotic genes (Ccnb2, Cdc20, and Cdk1) and the proliferation-related nuclear antigen Mki67 were observed with peak expression occurring between 1 and 7 days PB exposure. All these transcriptional responses were absent in CAR(KO)-PXR(KO) mouse livers and largely reversible in wild-type and CAR(h)-PXR(h) mouse livers following 91 days of PB exposure and a subsequent 4-week recovery period. Furthermore, PB-mediated upregulation of the noncoding RNA Meg3, which has recently been associated with cellular pluripotency, exhibited a similar dose response and perivenous hepatocyte-specific localization in both wild-type and CAR(h)-PXR(h) mice. Thus, mouse livers coexpressing human CAR and PXR support both the xenobiotic metabolizing and the proliferative transcriptional responses following exposure to PB.

Functional roles of Lgr4 and Lgr5 in embryonic gut, kidney and skin development in mice

Lgr4 and Lgr5 are known markers of adult and embryonic tissue stem cells in various organs. However, whether Lgr4 and Lgr5 are important for embryonic development remains unclear. To study their functions during intestinal crypt, skin and kidney development we now generated mice lacking either Lgr4 (Lgr4KO), Lgr5 (Lgr5KO) or both receptors (Lgr4/5dKO). E16.5 Lgr4KO mice displayed complete loss of Lgr5+/Olfm4+intestinal stem cells, compromised Wnt signaling and impaired proliferation and differentiation of gut epithelium. Similarly, E16.5 Lgr4KO mice showed reduced basal cell proliferation and hair follicle numbers in the developing skin, as well as dilated kidney tubules and ectatic Bowman׳s spaces. Although Lgr4KO and Lgr5KO mice both died perinatally, Lgr5 deletion did not compromise embryonic development of gut, kidney or skin. Concomitant deletion of Lgr4 and Lgr5 did not prevent perinatal lethality, in contrast to a previous report that suggested rescue of Lgr5 KO perinatal lethality by a hypomorphic Lgr4 mutant. While the double deletion did not further promote the phenotypes observed in Lgr4KO intestines, impaired kidney cell proliferation, reduced epidermal thickness, loss of Lgr5+follicular epithelium and impaired hair follicle development were only observed in Lgr4/5dKO mice. This supports complementary functions of both receptors. Our findings clearly establish the importance of Lgr4 and Lgr5 during embryonic gut, skin and kidney development, with a dominant role of Lgr4.

Vascular origin of vildagliptin-induced skin effects in Cynomolgus monkeys: pathomechanistic role of peripheral sympathetic system and neuropeptide Y

The purpose of this article is to characterize skin lesions in cynomolgus monkeys following vildagliptin (dipeptidyl peptidase-4 inhibitor) treatment. Oral vildagliptin administration caused dose-dependent and reversible blister formation, peeling and flaking skin, erosions, ulcerations, scabs, and sores involving the extremities at ≥5 mg/kg/day and necrosis of the tail and the pinnae at ≥80 mg/kg/day after 3 weeks of treatment. At the affected sites, the media and the endothelium of dermal arterioles showed hypertrophy/hyperplasia. Skin lesion formation was prevented by elevating ambient temperature. Vildagliptin treatment also produced an increase in blood pressure and heart rate likely via increased sympathetic tone. Following treatment with vildagliptin at 80 mg/kg/day, the recovery time after lowering the temperature in the feet of monkeys and inducing cold stress was prolonged. Ex vivo investigations showed that small digital arteries from skin biopsies of vildagliptin-treated monkeys exhibited an increase in neuropeptide Y-induced vasoconstriction. This finding correlated with a specific increase in NPY and in NPY1 receptors observed in the skin of vildagliptin-treated monkeys. Present data provide evidence that skin effects in monkeys are of vascular origin and that the effects on the NPY system in combination with increased peripheral sympathetic tone play an important pathomechanistic role in the pathogenesis of cutaneous toxicity.

Heart structure-specific transcriptomic atlas reveals conserved microRNA-mRNA interactions

MicroRNAs are short non-coding RNAs that regulate gene expression at the post-transcriptional level and play key roles in heart development and cardiovascular diseases. Here, we have characterized the expression and distribution of microRNAs across eight cardiac structures (left and right ventricles, apex, papillary muscle, septum, left and right atrium and valves) in rat, Beagle dog and cynomolgus monkey using microRNA sequencing. Conserved microRNA signatures enriched in specific heart structures across these species were identified for cardiac valve (miR-let-7c, miR-125b, miR-127, miR-199a-3p, miR-204, miR-320, miR-99b, miR-328 and miR-744) and myocardium (miR-1, miR-133b, miR-133a, miR-208b, miR-30e, miR-499-5p, miR-30e*). The relative abundance of myocardium-enriched (miR-1) and valve-enriched (miR-125b-5p and miR-204) microRNAs was confirmed using in situ hybridization. MicroRNA-mRNA interactions potentially relevant for cardiac functions were explored using anti-correlation expression analysis and microRNA target prediction algorithms. Interactions between miR-1/Timp3, miR-125b/Rbm24, miR-204/Tgfbr2 and miR-208b/Csnk2a2 were identified and experimentally investigated in human pulmonary smooth muscle cells and luciferase reporter assays. In conclusion, we have generated a high-resolution heart structure-specific mRNA/microRNA expression atlas for three mammalian species that provides a novel resource for investigating novel microRNA regulatory circuits involved in cardiac molecular physiopathology.

How to manage recurrent falls in clinical practice: guidelines of the French Society of Geriatrics and Gerontology

BACKGROUND

Health care professionals need a simple and pragmatic clinical approach for the management of recurrent fallers in clinical routine.

OBJECTIVE

To develop clinical practice recommendations with the aim to assist health care professionals, especially in primary care in the management of recurrent falls.

METHODS

A systematic English and French review was conducted using Medline, Embase, Pascal and Cochrane literature. Search included systematic reviews, meta-analyses, controlled trials, cohort studies, case-control studies and transversal studies published until July 31, 2008. The following Medical Subject Heading (MeSH) terms were used: "aged OR aged, 80 and over", "frail elderly", "Accidental Fall", "Mental Recall", and "Recurrent falls". The guidelines were elaborated according the Haute Autorite de Sante methods by a multidisciplinary working group comprising experts and practitioners.

RESULTS

A fall is an event that results in a person coming to rest inadvertently on the ground or floor or other lower level and should be considered as a recurrent event as soon as a subject reported at least two falls in a 12-month period. Recurrent falls impose a prompt and appropriate management with the first aim to systematically evaluate the severity of falls. The evaluation of fall severity should be based on a standardized questionnaire and physical examination. It is recommended not to perform cerebral imaging in the absence of specific indication based on the clinical examination and to reevaluate the subject within a week after the fall. Prior to any intervention and after an evaluation of signs of severity, it is recommended to systematically assess the risk factors for falls. This evaluation should be based on the use of validated and standardized tests. The education of recurrent fallers and their care givers is required in order to implement appropriate intervention. In the event of a gait and/or balance disorders, it is recommended to prescribe physiotherapy. A regular physical activity should be performed with low to moderate intensity exercise. It is recommended to perform rehabilitation exercises with a professional, between therapy sessions and after each session, in order to extend rehabilitation benefits to the daily life.

CONCLUSION

The clinical guidelines focused on management (i.e., diagnosis, assessment and treatment) of recurrent falls in clinical routine. They provide answers to the following clinical questions: 1) How to define recurrent falls? 2) How to identify severe falls? 3) How to assess recurrent falls? and 4) How to treat recurrent falls?

Disorder effects in pnictides: a tunneling spectroscopy study

We present the synthesis and the tunneling spectroscopy study of superconducting FeSe(0.5)Te(0.5) (T(c) = 14 K), SmFeAsO(0.85) (T(c) = 54 K) and SmFeAsO(0.9)F(0.1) (T(c) = 45 K). The samples were characterized by Rietveld refinement of x-ray diffraction patterns and transport as well as temperature-dependent magnetic measurements. Tunneling experiments on FeSe(0.5)Te(0.5) revealed a single superconducting gap ∼ 1 meV in BCS-like tunneling conductance spectra. In SmFeAsO(0.85) and SmFeAsO(0.9)F(0.1), however, more complex spectra were observed, characterized by two gap-like structures at ∼ 4 and ∼ 10 meV. These spectra are qualitatively understood assuming a two-band superconductor with a 's ±' order parameter. We show that, depending on the sign relation between the pairing amplitudes in the two bands, the interband quasiparticle scattering has a crucial effect on the shape of the tunneling spectra. On the other hand, single-gap spectra found in FeSe(0.5)Te(0.5) are more compatible with a disorder-induced 's '-wave gap, due to the Se-Te substitution.

Scanning tunneling spectroscopy on the novel superconductor CaC6

We present scanning tunneling microscopy and spectroscopy of the newly discovered superconductor CaC6. The tunneling conductance spectra, measured between 3 and 15 K, show a clear superconducting gap in the quasiparticle density of states. The gap function extracted from the spectra is in good agreement with the conventional BCS theory with Delta0=1.6+/-0.2 meV. The possibility of gap anisotropy and two-gap superconductivity is also discussed. In a magnetic field, direct imaging of the vortices allows us to deduce a coherence length in the ab plane xiab approximately 33 nm.

Dual-task-related gait changes in the elderly: does the type of cognitive task matter?

Dual-task-related gait changes among older adults while they perform spoken verbal tasks have been reported frequently. The authors examined whether the type of walking-associated spoken verbal task matters for dual-task-related gait changes in 16 older adults classified as transitionally frail. Mean stride time increased significantly when they walked and performed an arithmetic or a verbal fluency task compared with when they only walked (p < .001), whereas the coefficients of variation increased significantly only when they walked and performed the arithmetic task (p = .005) but not the verbal fluency task (p = .134). Those findings suggest that stride time variability under a dual-task condition depends on the type of walking-associated spoken verbal task.

Similar planning strategies for whole-body and arm movements performed in the sagittal plane

The present paper looks for kinematic similarities between whole-body and arm movements executed in the sagittal plane. Eight subjects performed sit-to-stand (STS) and back-to-sit (BTS) movements at their preferred speed in the sagittal plane. Kinematics analysis focused on shoulder motion revealed that STS was composed of a straight, forward displacement followed by a curved, upward displacement while BTS was characterized by a curved, downward and straight, backward displacement. Curvature of the upward displacement was significantly greater than the downward one. Analysis of shoulder-velocity profiles showed that movement duration was significantly longer for BTS compared with STS and that the shape of the velocity profiles changed when subjects performed an STS compared with a BTS movement. Velocity profiles of the upward and downward displacements also differed; the relative acceleration duration (acceleration duration divided by movement duration during the vertical motion) was smaller for the upward compared with the downward displacement. The present results are in accordance with previous findings concerning the execution of vertical arm movements and suggest that the CNS uses similar motor plans for the performance of arm and whole-body movements in the sagittal plane.

[Effectiveness of falls prevention strategies for elderly subjects who live in the community with performance assessment of physical activities (before-after)]

OBJECTIVES

The development of falls prevention strategies is an essential health concern in elderly people. However, a global consensus does not exist for elderly subjects who live independently in the community. The aim of the study was to evaluate the benefit of an exercises program.

MATERIALS AND METHODS

A control group (153 subjects) and an "Intervention" group (150 subjects) were tested before and after a 1-year prospective study. The "Intervention" group performed ten training sessions of physical activity, based on balance, muscular activity and coordination. We compared the incidence of falls, and the performances in several tests between the two groups.

RESULTS

The clinical features were similar between the two groups: mean age 71 years, 83% of females, subjects who were independent for activities of daily living. However, all subjects presented risk for factors for falls: 38% were not able to maintain the unipodal position more than five seconds, 29% had already fallen during the previous year. For the "Intervention" group, the comparison of the performances before and after the physical activity program showed significant increases (p < 0.001) for all the tests, and specifically for the unipodal position and for the exercises performed with eyes closed. After one year follow-up, the incidence rate of falls was lower in the "Intervention" group compared with the control group, but the difference was not significant (p = 0.32). However, falls occurred significantly latter in the "Intervention" group (p = 0.02).

CONCLUSION

Ten training sessions of physical activity allowed to improve the performance of elderly people in several tests. This result suggests that a fall prevention program based on collective and regular exercises, may be efficient for elderly subjects who still have an active and independent way of live.

[Influence of a specific cognitive task on spatial-temporal walking parameters in elderly frail individuals]

OBJECTIVE

Walking is a complex voluntary rhythmic motor behaviour. Its implicit nature suggests that reduced attention resources are required for its execution. The aim of this study was to demonstrate that, to perform a mental calculation while walking, might modify the spatial-temporal parameters of walking in fragile elderly patients.

METHODS

We compared the walking, in a straight line over a distance of 10 meters, of 30 fragile elderly subjects (mean age 82.6 +/- 7.1 years) with that of 30 healthy controls (mean age 37.5 +/- 11.5 years). Two walking conditions were studied: with and without a counting task. The time, number of steps, lateral deviations and stops were recorded on a video camera.

RESULTS

The condition of a double-task provoked three types of effects on walking: an increase in time and the number of steps in both groups, but significantly greater in the elderly patients than in the control group of patients (6.4 s and 4.6 steps in the elderly versus 0.5 s and 0.4 steps in the controls); a reduction in the cadence and length of the step, only significant in the elderly patients, and a significant increase in the number of lateral deviations and stops in the double-task condition in the elderly patients.

CONCLUSION

Globally, these results indicate that walking requires more attention resources in the elderly than in the middle-aged. The loss of the implicit character of walking to the benefit of cognitive attention resources may partly explain the high risk of falling in fragile elderly subjects.

[Development of a clinical test of gait in frail elderly by a cognitive approach of locomotion]

OBJECTIVE

From a cognitive approach of locomotion, we studied the feasibility and the reproducibility of a clinical test of gait which is devoted to predict fall.

METHODOLOGY

With a cross-sectional design, we studied the gait of 30 old subjects (average age 82.6+/-7.1 years). The gait course consisted of a 10m length in a well light room, with regular walking shoes. Two conditions were examined: walking with and without explicit cognitive task (mental arithmetic and verbal flow task). Time (seconds) and number of steps were collected by two operators Deviations and stops were video-taped. Number of figures was recorded with a tape recorder. The difficulty to perform gait conditions was estimated by each subject with a quotation ranging from 0 (easy gait) to 10 (difficult gait).

RESULTS

Increases of time, steps, deviations and stops were observed when gait was associated to a cognitive task (6.4 seconds and 4.6 steps with mental arithmetic; 10.5 seconds and 6.7 steps with verbal flow task). All subjects managed this test. These results were reproducible across tests and operators. Walking with mental arithmetic was the most easy gait condition for subjects.

CONCLUSIONS

The simplicity and the reproducibility of this test make it as adequate instrument of gait evaluation in geriatrics. Walking with mental arithmetic is the condition that must to be used. Validation of its predictive value for fall in frail elderly subjects remains to be shown.

Heterogeneity in hepatic transport of somatostatin analog octapeptides

Hepatic transport of the synthetic somatostatin analog octreotide-SMS 201-995, (D)Phe-Cys-Phe-(D)Trp-Lys-Thr-Cys-Throl--and its novel derivative N-alpha-(alpha-D-glucosyl(1-4)-1-deoxy-D-fructosyl)-octreotide--SD Z CO-611, N-alpha-(alpha-D-glucosyl(1-4)-1-deoxy-D-fructosyl)-(D)Phe-Cys-Phe- (D)Trp-Lys-Thr-Cys-Throl--was studied. In rats SMS 201-995 showed a plasma elimination half-life of 1.2 +/- 0.2 hr; that of SDZ CO-611 was 1.9 +/- 0.3 hours. Within 120 min 66% of a mesenterically injected 4.4-nmol dose of SMS 201-995 was excreted in bile, but only 5.3% of SDZ CO-611 was excreted in bile. Biliary concentration of SMS 201-995 showed a maximum enrichment of 540-fold +/- 75-fold over peripheral blood concentration, indicating hepatic transport mechanisms different from simple diffusion. Comparison of plasma profiles of both peptides after mesenteric and femoral administration demonstrated the relative importance of hepatic extraction for SMS 201-995 but not for SDZ CO-611. The mode of extraction was studied by means of multiple-indicator dilution in isolated perfused rat liver, with inulin as nonpermeable marker. Ratio plots, ln([inulin]/[peptide]) vs. time, exhibited decreasing slopes for SMS 201-995, suggesting very rapid binding to hepatocyte membranes. The slope of the ratio plot of (inulin/SDZ CO-611) was almost zero even at low doses (down to 0.2 microgram), implying mainly extracellular distribution and nonhepatic elimination. Binding assays indicated the absence of somatostatin receptors in sinusoidal hepatocyte membranes. However, SMS 201-995 and SDZ CO-611 bound with high affinity to somatostatin receptors in rat cortical membranes. Multiple-indicator dilution experiments in presence of increasing cholyltaurine concentrations suggested an interaction of SMS 201-995 with sinusoidal bile salt transport. In isolated hepatocytes, uptake of SMS 201-995 was saturable and showed mutual inhibition with cholyltaurine. The results indicate that SMS 201-995 transport is different from receptor mediated endocytosis as known for peptide hormones and elimination pathways of SDZ CO-611 other than biliary excretion.

Characteristics of bile salt uptake into skate hepatocytes

The substrate specificity for the transporter that mediates the hepatic uptake of organic anions in freshly isolated hepatocytes of the elasmobranch little skate (Raja erinacea) was determined for bile salts and bile alcohols. The Na(+)-independent transport system exhibits a substrate specificity, which is different from the specificity of Na(+)-dependent bile salt transport in mammals. Unconjugated and conjugated di- and tri-hydroxylated bile salts inhibit uptake of cholyltaurine and cholate competitively. Inhibition is significantly greater with unconjugated as opposed to glycine- or taurine-conjugated bile salts. However, the number of hydroxyl groups in the steroid moiety of the bile salts has only minor influences on the inhibition by the unconjugated bile salts. Since the transport system seems to represent an archaic organic-anion transport system, other anions, such as dicarboxylates, amino acids and sulphate, were also tested, but had no inhibitory effect on bile salt uptake. To clarify whether bile alcohols, the physiological solutes in skate bile, share this transport system, cholyltaurine transport was studied after addition of 5 beta-cholestane-3 beta,5 alpha,6 beta-triol, 5 alpha-cholestan-3 beta-ol and 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha-triol. These bile alcohols inhibit cholyltaurine uptake non-competitively. In contrast, uptake of 5 beta-cholestane-3 alpha,7 alpha,12 alpha-triol, which is Na(+)-independent, is not inhibited by cholyltaurine. The findings further characterize a Na(+)-independent organic-anion transport system in skate liver cells, which is not shared by bile alcohols and has preference for unconjugated lipophilic bile salts.