Molecular features of the ligand-free GLP-1R, GCGR and GIPR in complex with Gs proteins

Class B1 G protein-coupled receptors (GPCRs) are important regulators of many physiological functions such as glucose homeostasis, which is mainly mediated by three peptide hormones, i.e., glucagon-like peptide-1 (GLP-1), glucagon (GCG), and glucose-dependent insulinotropic polypeptide (GIP). They trigger a cascade of signaling events leading to the formation of an active agonist-receptor-G protein complex. However, intracellular signal transducers can also activate the receptor independent of extracellular stimuli, suggesting an intrinsic role of G proteins in this process. Here, we report cryo-electron microscopy structures of the human GLP-1 receptor (GLP-1R), GCG receptor (GCGR), and GIP receptor (GIPR) in complex with Gs proteins without the presence of cognate ligands. These ligand-free complexes share a similar intracellular architecture to those bound by endogenous peptides, in which, the Gs protein alone directly opens the intracellular binding cavity and rewires the extracellular orthosteric pocket to stabilize the receptor in a state unseen before. While the peptide-binding site is partially occupied by the inward folded transmembrane helix 6 (TM6)-extracellular loop 3 (ECL3) juncture of GIPR or a segment of GCGR ECL2, the extracellular portion of GLP-1R adopts a conformation close to the active state. Our findings offer valuable insights into the distinct activation mechanisms of these three important receptors. It is possible that in the absence of a ligand, the intracellular half of transmembrane domain is mobilized with the help of Gs protein, which in turn rearranges the extracellular half to form a transitional conformation, facilitating the entry of the peptide N-terminus.

Structural analysis of the dual agonism at GLP-1R and GCGR

Glucagon-like peptide-1 receptor (GLP-1R) and glucagon receptor (GCGR), two members of class B1 G protein-coupled receptors, play important roles in glucose homeostasis and energy metabolism. They share a high degree of sequence homology but have different functionalities. Unimolecular dual agonists of both receptors developed recently displayed better clinical efficacies than that of monotherapy. To study the underlying molecular mechanisms, we determined high-resolution cryo-electron microscopy structures of GLP-1R or GCGR in complex with heterotrimeric Gs protein and three GLP-1R/GCGR dual agonists including peptide 15, MEDI0382 (cotadutide) and SAR425899 with variable activating profiles at GLP-1R versus GCGR. Compared with related structures reported previously and supported by our published pharmacological data, key residues responsible for ligand recognition and dual agonism were identified. Analyses of peptide conformational features revealed a difference in side chain orientations within the first three residues, indicating that distinct engagements in the deep binding pocket are required to achieve receptor selectivity. The middle region recognizes extracellular loop 1 (ECL1), ECL2, and the top of transmembrane helix 1 (TM1) resulting in specific conformational changes of both ligand and receptor, especially the dual agonists reshaped ECL1 conformation of GLP-1R relative to that of GCGR, suggesting an important role of ECL1 interaction in executing dual agonism. Structural investigation of lipid modification showed a better interaction between lipid moiety of MEDI0382 and TM1-TM2 cleft, in line with its increased potency at GCGR than SAR425899. Together, the results provide insightful information for the design and development of improved therapeutics targeting these two receptors simultaneously.

Structural insights into ligand recognition and subtype selectivity of the human melanocortin-3 and melanocortin-5 receptors

Members of the melanocortin receptor (MCR) family that recognize different melanocortin peptides mediate a broad spectrum of cellular processes including energy homeostasis, inflammation and skin pigmentation through five MCR subtypes (MC1R-MC5R). The structural basis of subtype selectivity of the endogenous agonist γ-MSH and non-selectivity of agonist α-MSH remains elusive, as the two agonists are highly similar with a conserved HFRW motif. Here, we report three cryo-electron microscopy structures of MC3R-G_s in complex with γ-MSH and MC5R-G_s in the presence of α-MSH or a potent synthetic agonist PG-901. The structures reveal that α-MSH and γ-MSH adopt a "U-shape" conformation, penetrate into the wide-open orthosteric pocket and form massive common contacts with MCRs via the HFRW motif. The C-terminus of γ-MSH occupies an MC3R-specific complementary binding groove likely conferring subtype selectivity, whereas that of α-MSH distances itself from the receptor with neglectable contacts. PG-901 achieves the same potency as α-MSH with a shorter length by rebalancing the recognition site and mimicking the intra-peptide salt bridge in α-MSH by cyclization. Solid density confirmed the calcium ion binding in MC3R and MC5R, and the distinct modulation effects of divalent ions were demonstrated. Our results provide insights into ligand recognition and subtype selectivity among MCRs, and expand the knowledge of signal transduction among MCR family members.

Structural insights into multiplexed pharmacological actions of tirzepatide and peptide 20 at the GIP, GLP-1 or glucagon receptors

Glucose homeostasis, regulated by glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1) and glucagon (GCG) is critical to human health. Several multi-targeting agonists at GIPR, GLP-1R or GCGR, developed to maximize metabolic benefits with reduced side-effects, are in clinical trials to treat type 2 diabetes and obesity. To elucidate the molecular mechanisms by which tirzepatide, a GIPR/GLP-1R dual agonist, and peptide 20, a GIPR/GLP-1R/GCGR triagonist, manifest their multiplexed pharmacological actions over monoagonists such as semaglutide, we determine cryo-electron microscopy structures of tirzepatide-bound GIPR and GLP-1R as well as peptide 20-bound GIPR, GLP-1R and GCGR. The structures reveal both common and unique features for the dual and triple agonism by illustrating key interactions of clinical relevance at the near-atomic level. Retention of glucagon function is required to achieve such an advantage over GLP-1 monotherapy. Our findings provide valuable insights into the structural basis of functional versatility of tirzepatide and peptide 20.

Multi-targeting agonists at GIPR, GLP-1R or GCGR are pursued vigorously. Here, the authors report cryo-EM structures of tirzepatide-bound GIPR and GLP-1R, peptide 20-bound GIPR, GLP-1R and GCGR, revealing the molecular basis of their multiplexed pharmacological actions.

Molecular insights into ago-allosteric modulation of the human glucagon-like peptide-1 receptor

The glucagon-like peptide-1 (GLP-1) receptor is a validated drug target for metabolic disorders. Ago-allosteric modulators are capable of acting both as agonists on their own and as efficacy enhancers of orthosteric ligands. However, the molecular details of ago-allosterism remain elusive. Here, we report three cryo-electron microscopy structures of GLP-1R bound to (i) compound 2 (an ago-allosteric modulator); (ii) compound 2 and GLP-1; and (iii) compound 2 and LY3502970 (a small molecule agonist), all in complex with heterotrimeric G_s. The structures reveal that compound 2 is covalently bonded to C347 at the cytoplasmic end of TM6 and triggers its outward movement in cooperation with the ECD whose N terminus penetrates into the GLP-1 binding site. This allows compound 2 to execute positive allosteric modulation through enhancement of both agonist binding and G protein coupling. Our findings offer insights into the structural basis of ago-allosterism at GLP-1R and may aid the design of better therapeutics.

The glucagon-like peptide-1 (GLP-1) receptor is a key regulator of glucose homeostasis and a drug target for type 2 diabetes but available GLP-1R agonists are suboptimal due to several side-effects. Here authors report the cryo-EM structure of GLP-1R bound to an ago-allosteric modulator in complex with heterotrimeric G_s which offers insights into the molecular details of ago-allosterism.

Structural basis for activation of the growth hormone-releasing hormone receptor

Growth hormone-releasing hormone (GHRH) regulates the secretion of growth hormone that virtually controls metabolism and growth of every tissue through its binding to the cognate receptor (GHRHR). Malfunction in GHRHR signaling is associated with abnormal growth, making GHRHR an attractive therapeutic target against dwarfism (e.g., isolated growth hormone deficiency, IGHD), gigantism, lipodystrophy and certain cancers. Here, we report the cryo-electron microscopy (cryo-EM) structure of the human GHRHR bound to its endogenous ligand and the stimulatory G protein at 2.6 Å. This high-resolution structure reveals a characteristic hormone recognition pattern of GHRH by GHRHR, where the α-helical GHRH forms an extensive and continuous network of interactions involving all the extracellular loops (ECLs), all the transmembrane (TM) helices except TM4, and the extracellular domain (ECD) of GHRHR, especially the N-terminus of GHRH that engages a broad set of specific interactions with the receptor. Mutagenesis and molecular dynamics (MD) simulations uncover detailed mechanisms by which IGHD-causing mutations lead to the impairment of GHRHR function. Our findings provide insights into the molecular basis of peptide recognition and receptor activation, thereby facilitating the development of structure-based drug discovery and precision medicine.

Growth hormone-releasing hormone (GHRH) controls metabolism and tissue growth through binding to the cognate receptor (GHRHR). Here authors report the structure of the human GHRHR bound to its endogenous ligand and the stimulatory G protein which reveals a characteristic hormone recognition pattern of GHRH by GHRHR.

Safety, feasibility, and effect of an enhanced nutritional support pathway including extended preoperative and home enteral nutrition in patients undergoing enhanced recovery after esophagectomy: a pilot randomized clinical trial

The aims of this pilot study are to evaluate the feasibility, safety, and effectiveness of conducting an enhanced nutritional support pathway including extended preoperative nutritional support and one month home enteral nutrition (HEN) for patients who underwent enhanced recovery after esophagectomy. We implemented extended preoperative nutritional support and one month HEN after discharge for patients randomized into an enhanced nutrition group and implemented standard nutritional support for patients randomized into a conventional nutrition group. Except the nutritional support program, both group patients underwent the same standardized enhanced recovery after surgery programs of esophagectomy based on published guidelines. Patients were assessed at preoperative day, postoperative day 7 (POD7), and POD30 for perioperative outcomes and nutritional status. To facilitate the determination of an effect size for subsequent appropriately powered randomized clinical trials and assess the effectiveness, the primary outcome we chose was the weight change before and after esophagectomy. Other outcomes including body mass index (BMI), lean body mass (LBM), appendicular skeletal muscle mass index (ASMI), nutrition-related complications, and quality of life (QoL) were also analyzed. The intention-to-treat analysis of the 50 randomized patients showed that there was no significant difference in baseline characteristics. The weight (-2.03 ± 2.28 kg vs. -4.05 ± 3.13 kg, P = 0.012), BMI (-0.73 ± 0.79 kg/m2 vs. -1.48 ± 1.11 kg/m2, P = 0.008), and ASMI (-1.10 ± 0.37 kg/m2 vs. -1.60 ± 0.66 kg/m2, P = 0.010) loss of patients in the enhanced nutrition group were obviously decreased compared to the conventional nutrition group at POD30. In particular, LBM (48.90 ± 9.69 kg vs. 41.96 ± 9.37 kg, p = 0.031) and ASMI (7.56 ± 1.07 kg/m2 vs. 6.50 ± 0.97 kg/m2, P = 0.003) in the enhanced nutrition group were significantly higher compared to the conventional nutrition group at POD30, despite no significant change between pre- and postoperation. In addition, European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 scores revealed that enhanced nutritional support improved the QoL of patients in physical function (75.13 ± 9.72 vs. 68.33 ± 7.68, P = 0.009) and fatigue symptom (42.27 ± 9.93 vs. 49.07 ± 11.33, P = 0.028) compared to conventional nutritional support. This pilot study demonstrated that an enhanced nutritional support pathway including extended preoperative nutritional support and HEN was feasible, safe, and might be beneficial to patients who underwent enhanced recovery after esophagectomy. An appropriately powered trial is warranted to confirm the efficacy of this approach.

A novel controlled drug delivery system based on alginate hydrogel/chitosan micelle composites

In this study, we present a novel cross-linked unimolecular micelle based on chitosan. For controlling drug delivery via oral administration, emodin (EMO) encapsulated micelles were loaded into sodium alginate hydrogel matrix to construct the pH-sensitive hydrogel/micelle composites. The optimized formulation of micelle that consists of 8.06% CaCl₂, 1.71% chitosan and 26.52% β-GP was obtained by the combination of Box-Behnken experimental design and response surface methodology. The morphological analysis showed that the micelles exhibited a smaller diameter of about 80nm in aqueous solution, but dilated to 100-200nm in hydrogel owing to the formation of polyelectrolyte complexes. The physical characteristics in simulated digestive fluids were investigated, demonstrating that the ratio of hydrogel to micelle distinctly affected swelling, degradation and in vitro drug release behaviors. The hydrogel/micelle (1:1) exhibited a sustained-release profile, while hydrogel/micelle (3:1) exhibited a colon-specific profile. Their corresponding release mechanisms revealed that the release of drug from these two formulations followed a complex process, in which several mechanisms were involved or occurred simultaneously. These results demonstrated that the pH-sensitive hydrogel/micelle composites constructed with biocompatible materials can be a promising sustained-release or site-specific drug delivery system for instable or hydrophobic drugs.

[Characterization of N-linked glycosylation sites on envelope proteins of simian/human immunodeficiency virus in peripheral blood of Chinese rhesus macaques during acute infection]

Objective: To investigate the number and distribution of N-linked glycosylation sites of simian/human immunodeficiency virus envelope proteins(SHIV_SF162P3)and SHIV transmission. Methods: Two female adult Chinese rhesus macaques(4 years old)were intravenously inoculated with 300 TCID50 SHIV_SF162P3. The macaques weighed 4 and 5 kg and were identified as Rh1 and Rh2. We collected plasma samples at days 3, 7, 10, 14, 17, 21, 24, 28, 35, 42, 49, 56, 63, 70 and 77 post-challenge. Subsequently, we monitored plasma viral load by real-time PCR after viral RNA isolation and cDNA synthesis. We amplified the full-length envelope gene by single genome amplification(SGA)at days 7, 14, 28 and 77. BioEdit, MEGA, and the HIV Databases were used to analyze envelope sequences. Sequence diversity and N-linked glycosylation sites were compared between virus stock and plasma viruses of the two macaques. Results: A total of 55 env sequences were obtained from virus stock and their average pairwise distances were(0.166 6± 0.096 3)%. Viral loads peaked at 7.68 and 7.49 log10 copies/ml at day 10 and reached the set point at day 42(4.27 and 4.81 log10 copies/ml). The percentages of envelope sequences containing 25 potential N-linked glycosylation sites(PNGSs)were 83%(20/24)and 94%(29/31)in Rh1 and Rh2, respectively, at day 7; these were significantly higher than the proportion in SHIV_SF162P3 stock(49%(27/55)). Viral diversity after infection increased with time whereas the proportion of sequences containing 25 PNGSs decreased and sequences containing 27 PNGSs gradually increased. In Rh1, the percentage of sequences containing 27 PNGSs increased to 29% at day 28 and reached 35% at day 77 in Rh2. By analyzing the number of PNGSs in the V1-V5 regions, we found that PNGS variation mainly occurred in the V4 loop. Compared with sequences containing 27 PNGSs, a seven amino acid(TWNNTIG)deletion was found in the V4 loop, which resulted in a loss of two PNGSs at positions 392 and 396. Conclusion: Low glycosylation of the SHIV_SF162P3 V4 loop may facilitate spread of the SHIV virus whereas viruses with highly glycosylated V4 loops showed replication advantages after infection.

Inhibition of transforming growth factor beta-activated kinase 1 confers neuroprotection after traumatic brain injury in rats

The transforming growth factor beta-activated kinase 1 (TAK1), a member of the Mitogen-activated protein kinase kinase kinase family, is characterized as a key regulator in inflammatory and apoptosis signaling pathways. The aim of the present study was to evaluate the role of the TAK1 pathway in experimental traumatic brain injury (TBI) in rats. Adult male Sprague-Dawley rats were subjected to TBI using a modified Feeney's weight-drop model. The time course showed that a significant increase of TAK1 and p-TAK1 expression in the cortex after TBI. Moreover, TBI induced TAK1 redistribution both in neurons and astrocytes of the lesion boundary zone. The effects of specific inhibition of the TAK1 pathway by 5Z-7-oxozeaenol (OZ, intracerebroventricular injection at 10min post-trauma) on histopathological and behavioral outcomes in rats were assessed at 24h post injury. The number of TUNEL-positive stained cells was diminished and neuronal survival and neurological function were improved with OZ treatment. Biochemically, the high dose of OZ significantly reduced the levels of TAK1 and p-TAK1, further decreased nuclear factor-κB and activator protein 1 activities and the release of inflammatory cytokines. In addition, we found that both 10min and 3h post-trauma OZ therapies could markedly improve neurological function and neuronal survival after long-term survival. These results revealed that the TAK1 pathway is activated after experimental TBI and the inhibitor OZ affords significant neuro- protection and amelioration of neurobehavioral deficits after experimental TBI, suggesting a potential rationale for manipulating this pathway in clinical practice.

Hemoglobin Decline in Chemotherapy Patients Prior to and after Policy Changes Affecting Use of Erythropoiesis-Stimulating Agents: 2006 – 2009

OBJECTIVE: Since 2007, the use of erythropoiesis-stimulating agents (ESAs) to treat anemia in cancer patients receiving chemotherapy has been increasingly restricted in the USA. This study assessed hemoglobin (Hb) decline over time among chemotherapy patients. METHODS: Episodes of chemotherapy care were identified in a large US-oncology electronic medical record database; weekly Hb levels were computed in the first 8 weeks. Unadjusted and adjusted proportions of patient-weeks with Hb decline > 1 g/dl (i.e. representing clinically significant decline) within 1 or 2 weeks were analyzed. RESULTS: Between 2006 and 2009, unadjusted proportions of patient-weeks with Hb decline > 1 g/dl increased (1-week, from 12.7% to 14.9%; 2-week, from 19.3% to 26.3%). Adjusted 1-week proportions in 2007 were similar to 2006, but increased in 2008 (odds ratio [OR] 1.135; 95% confidence intervals [CI] 1.067, 1.208) and in 2009 (OR 1.235; 95% CI 1.094, 1.395). Adjusted 2-week proportions had the same pattern. CONCLUSIONS: Since restrictions on ESA use were introduced in the USA, more patients have experienced a clinically significant Hb decline after chemotherapy initiation. Initiating anemia therapy at the earliest indicated opportunity may help reduce the risk of such declines.

P4-13-01: Pain Severity and Analgesic Use Associated with Skeletal-Related Events in Patients with Advanced Breast Cancer and Bone Metastases

Background: Skeletal-related events (SREs), which include pathologic fracture (PF), radiation to bone (RB), surgery to bone (SB), and spinal cord compression (SCC), occur frequently in patients with bone metastases and can lead to debilitating clinical consequences such as functional impairment and bone pain. Denosumab (XGEVA®) is a fully human monoclonal antibody against RANKL, shown to be superior to zoledronic acid (ZA; Zometa®) for the prevention of SREs in patients with solid tumors. Denosumab also delayed the onset of moderate or severe pain compared with ZA. The pain severity and analgesic use associated with each type of SRE were assessed in patients with advanced breast cancer and bone metastases.

Methods: Eligible patients received denosumab 120 mg SC or ZA 4 mg (adjusted for renal function) IV every 4 weeks in a randomized, multinational, double-blind, double-dummy trial. Patient-reported pain was assessed with the Brief Pain Inventory (BPI; 0 no pain to 10 severe pain) at baseline (BL) and at each monthly visit. Opioid and non-opioid analgesic use was recorded and scored using the Analgesic Quantification Algorithm (AQA; 0 no analgesic use to 7 > 600mg oral morphine equivalent/day). Data from the two treatment arms were pooled for this analysis. Pain and analgesic use were evaluated from 6 months prior to and 6 months after the first on-study SRE for each patient. The comparator group included patients without an SRE and was centered at the median time from randomization to first SRE by SRE type, with corresponding 12 month assessments. The proportion of patients with moderate/severe pain (BPI worst pain score > 4) and proportion of patients shifting from no/low analgesic use (AQA ≤ 2) at baseline to strong opioid use (AQA ≥ 3) were reported by month and by SRE type, and are summarized by mean relative change (%) across the time period.

Results: In total, 687 patients with first on-study SRE occurrences (PF=450, RB=201, SCC=16, SB=20) were analyzed. A similar proportion of patients with and without a PF had moderate/severe pain, but a higher proportion of patients with a PF shifted from no/low analgesic use to strong opioid use (mean relative increase 80%). Starting 3 months prior to the event, more patients with RB than those without had moderate/severe pain (27% mean relative increase) and shifted from no/low analgesic use to strong opioid use (mean relative increase 269%). Similar pain and analgesic use patterns were noted for patients with SCC (mean relative increase in pain: 63%; in AQA shift: 913%). More patients with SB than those without had moderate/severe pain in the 6 months leading on to SB (mean relative increase 51%). The difference was attenuated after SB, but during this time a much higher proportion of patients with SB shifted from no/mild opioid use to strong opioid use (mean relative increase 220%).

Discussion: SREs are associated with increased pain severity and analgesic use in patients with advanced breast cancer and bone metastasis. Patterns of pain severity and analgesic use differed by SRE type. Effective treatments to prevent SREs can decrease pain and the need for treatment with opioid analgesics.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-13-01.

Isotretinoin increases skin-surface levels of neutrophil gelatinase-associated lipocalin in patients treated for severe acne

BACKGROUND

A clear-cut need exists for safe and effective alternatives to the use of isotretinoin in severe acne. Lack of data regarding the specifics of isotretinoin's mechanism of action has hampered progress in this area. Recently, the protein neutrophil gelatinase-associated lipocalin (NGAL) has been identified as a mediator of the apoptotic effect of isotretinoin on sebocytes.

OBJECTIVES

To establish further the clinical relevance of NGAL and to elucidate the factors that induce NGAL expression in sebocytes.

METHODS

Methods were developed to isolate and quantify skin-surface levels of NGAL from normal subjects and patients with acne undergoing treatment with isotretinoin.

RESULTS

Patients with acne were found to have higher skin levels of NGAL compared with normal subjects. Studies in SEB-1 sebocytes indicate that NGAL expression is increased in response to Propionibacterium acnes and interleukin (IL)-1β. In patients, isotretinoin increases NGAL levels by 2·4-fold on the skin surface and this increase precedes decreases in sebum and P. acnes counts.

CONCLUSIONS

These data support the hypothesis that NGAL is an important mediator of the early effects of isotretinoin on the sebaceous glands and provide insights into the mechanisms that regulate NGAL expression in the skin.

TRAIL contributes to the apoptotic effect of 13-cis retinoic acid in human sebaceous gland cells

BACKGROUND

The full mechanism of action of isotretinoin [13-cis retinoic acid (13-cis RA)] in treating acne is unknown. 13-cis RA induces key genes in sebocytes that are involved in apoptosis, including Tumor necrosis factor Related Apoptosis Inducing Ligand (TRAIL).

OBJECTIVES

In this study, we investigated the role of 13-cis RA-induced TRAIL within SEB-1 sebocytes.

METHODS

Using 13-cis RA and recombinant human TRAIL (rhTRAIL) protein, we assessed induction of TRAIL and apoptosis in SEB-1 sebocytes, normal keratinocytes and patient skin biopsies.

RESULTS

Treatment with rhTRAIL protein increased TUNEL-positive staining in SEB-1 sebocytes. TRAIL siRNA significantly decreased the percentage of TUNEL-positive SEB-1 sebocytes in response to 13-cis RA treatment. Furthermore, TRAIL expression increased in the skin of patients with acne after 1 week of isotretinoin therapy compared with baseline. TRAIL expression localized within sebaceous glands. Unlike sebocytes, TRAIL protein expression was not increased in normal human epidermal keratinocytes in response to 13-cis RA, nor did rhTRAIL induce apoptosis in keratinocytes, suggesting that TRAIL is key in the sebocyte-specific apoptotic effects of 13-cis RA.

CONCLUSIONS

Taken together, our data suggest that TRAIL, like the neutrophil gelatinase-associated lipocalin, is involved in mediating 13-cis RA apoptosis of sebocytes.

[Study on the defluoridation of drinking water with synthetic hydroxyapatite]

Synthetic hydroxyapatite was used as a material for the defluoridation of drinking water. The defluoridation capacity, regeneration the capability of defluoridator and the corresponding parameters of defluoridation and regeneration have been studied with batch and column test. The results showed that the defluoridation capacity of synthetic hydroxyapatite on F- was 3.7-4.3 mg/g in batch test, 5.6 mg/g for break through (1.0 mg/L is considered as the break through point) in column test, and 10.7 mg/g for saturation in column test. The efficiency of regeneration was 46%-64% for saturated hydroxyapatite with surface-coating method.

Repairing segmental bone defects with living porous ceramic cylinders: an experimental study in dog femora

Twenty-one porous hydroxyapatite-tricalcium phosphate ceramic cylinders 1.5 cm long and 1.2 cm in diameter were swathed with fresh autogenetic periostea taken from 21 dogs and implanted in the same animals' muscles to get living ceramic bone substitutes. These substitutes contained autogenetic growth stimulators including osteoblasts and other multipotential cells. One month later, they were transferred to the segmental bone defect sites created in femoral diaphysis of the same animals. The roentgenograms showed that in time the boundaries between the cylinders and bone sections became vague. X-ray diffraction analysis indicated that the spectra of the samples tended to be similar to those of natural bones by 6 months postoperatively. Their bending strengths also increased gradually. After the cylinders were transferred from muscles to the bone defect sites, newly formed bone tissues rapidly increased and the cylinders gradually fused with the contacted bones 2 months later. By 4 and 6 months, bone tissue occupied most areas of the materials. The ratio of newly formed bone tissue had a large lead over the materials. Haversian systems were clearly observed and matured bone tissues filled the ceramic pores and connected with each other. Results suggested that culturing complexes that consist of autogenetic periostea and biomaterials, taking advantage of living organic culturing medium, should be an effective approach to get satisfactory bioactive bone substitutes. It also provides a basis for clinically repairing bone defects in bearing sites with complex bioceramics.

Osteoinductivity and biomechanics of a porous ceramic with autogenic periosteum

Twenty-one dogs were used to study the osteoinductivity and biomechanical properties of a biphasic porous ceramic with autogenic periosteum implanted in muscle. The ceramic implants were swathed in fresh periosteum derived from the same animals and implanted in the femur muscles. The other two groups of animals served as controls using the same material implanted in the femur bones and muscles without periosteum. Biomechanical measurements showed that, in the muscles, the experimental group had a higher bending strength than the unswathed group by the time the samples were harvested. Six months postoperatively, the strength of the samples in the experimental group had almost reached that of normal bones. The results of X-ray diffraction and infrared spectrometric analysis suggested that the degradation rate and speed of tricalcium phosphate (TCP) of the ceramic in the experimental group were faster than in the unswathed samples, but slower than in samples implanted in bones. The bone replacement and bone-inducing activity were excellent in the periosteum-swathed samples. Histologically, satisfactory bone repair was seen in the experimental samples. All results indicate that autogenic periosteum could increase bioactivity of ceramics in heterosites and improve bone formation in the surroundings of porous calcium phosphate ceramics. The data also infer that the complicated procedure of culturing bone growth factors with biomaterials in vitro to obtain bioactive grafts could be replaced by this relatively simple method.

The melanocortin 5 receptor is expressed in human sebaceous glands and rat preputial cells

Melanocortins regulate pigmentation, adrenal hormone secretion, immune functions, lipid metabolism, and feeding behaviors in rodents. These peptides include adrenocorticotrophic hormone, melanocyte stimulating hormone, beta-lipotrophin, and the endorphins. Lipid metabolism in sebaceous glands and preputial glands of rodents is regulated by alpha-melanocyte stimulating hormone, the major agonist for melanocortin receptors. Five melanocortin receptor subtypes have been identified that differ in their tissue localization and affinities for melanocortin ligands. Targeted disruption of the melanocortin 5 receptor in transgenic mice results in widespread dysfunction of exocrine glands, including a marked decrease in sebum production. A role for melanocortins in the modulation of human sebum production has not been established. The goal of this study is to determine which melanocortin receptors are expressed in human sebaceous glands. Messenger RNA was isolated from human sebaceous glands and the reverse transcriptase polymerase chain reaction was performed using primers specific for each of the melanocortin receptor subtypes. Transcripts were detected for the melanocortin 5 receptor. A polyclonal chicken antihuman antibody to the melanocortin 5 receptor localized to sebaceous glands, eccrine glands, hair follicles, and epidermis in human skin, rat skin, cultured human sebocytes, and rat preputial cells. Presence of the melanocortin 5 receptor protein in human sebaceous glands and rat preputial glands was further verified by Western blotting. These data support further investigation of the role of melanocortins in the regulation of human sebum production and support the use of the rat preputial system as an experimental model in sebaceous gland physiology.

[Characteristic immunodeficiency syndrome of rapid fatal type of simian immunodeficiency virus infected monkeys]

OBJECTIVE

To observe the characteristic immunodeficiency syndrome of the rapid fatal type of simian immunodeficiency virus (SIV) infected monkeys.

METHODS

Eighty rhesus monkeys and 4 cynomolgus monkeys were intravenously inoculated with SIVmac or SIVmac251. The virus isolation and viral titer, estimation by indirect immunofluroresence and viral antibody were determined periodically from monkeys' plasma; lymph node biopsies were performed for pathohistological examination.

RESULTS

Twelve out of 84 macaque (14.2%) died of rapid progressive type after inoculation of SIVmac and SIVmac251 in the duration 3 to 4 months. Dying monkeys showed persistent high viremia and low level titre antibody. Eight of 10 pathohistological changes showed severe depletion of lymphoid tissue in spleen and lymph nodes, there were remarkable immunodeficiency with opportunity infection. The other two monkeys appeared moderate lymphoid tissue deletion and hyperplasia without opportunity infections. The survived monkeys' (72/84) lymph nodes biopsies revealed hypoplasia of lymphoid tissue.

CONCLUSIONS

The characteristic immunodeficiency syndrome of rapid fatal type of simian immunodeficiency virus infected monkeys could be made with persistent high viremia, low level antibody, severe lymphoid tissue deletion in lymph nodes and spleen, as well as complicated opportunity infections.

[Influence of dexamethasone and epinephrine on glycogen content and cytosol glucocorticoid receptors in hyperthyroid rat liver]

The influence of hyperthyroidism on the action of drugs affecting rat liver glycogen content and its mechanism were investigated. The thyroid-induced hyperthyroidism of rat served as the model. In normal rats, dexamethasone (5 mg.kg-1, ip) increased the content of liver glycogen and decreased the Bmax of glucocorticoid receptors (GCR) in liver cytosol. These effects were minimized or even disappeared in hyperthyroid rat models. On the other hand, in normal rats, epinephrine (0.20 mg.kg-1, ip) decreased the content of liver glycogen. This effect was potentiated in hyperthyroid rat models. Epinephrine did not affect the Bmax of GCR in liver cytosol of normal and hyperthyroid rats. These results suggested that hyperthyroidism may be one of the causes effecting the individual differences of drug action, and that the influence of hyperthyroidism on the glycogen-increasing action of dexamethasone correlated well with the changes in glucocorticoid receptor. The mechanism of the influence of hyperthyroidism on the glycogen-decreasing action of epinephrine is to be further explored.

Effect of dimethyl sulfoxide on cytosolic calcium in cultured rat hepatocytes injured by D-galactosamine

D-galactosamine (Gal 0.5 mmol.L-1) made lactate dehydrogenase (LDH) leakage from the hepatocytes in monolayer-culture increase by 50%, Dimethyl sulfoxide (Me2SO 2% vol/vol) decreased the LDH leakage (P less than 0.05). The cytosolic free Ca2+ concentration ([Ca2+]c) of rat hepatocytes exposed to Gal 4 mmol.L-1 for 90 min in suspension culture increased about 2-fold (P less than 0.01). Me2SO (2%) antagonized this [Ca2+]c-increasing effect of Gal. These results verified directly that the [Ca2+]c of hepatocytes was increased in the early stage of Gal-induced hepatotoxicity, and suggested that the prevention or lightening of the disturbance in intracellular Ca2+ homeostasis may be, at least, one of the mechanisms of the protective action of Me2SO against Gal-induced hepatocyte injury.

[Observing cytoprotection of indomethacin on primary cultured hepatocytes of rats]

We observed previously that indomethacin induced hepatic protection against CCl4 and galactosamine in rats. In this work we further investigated this phenomenon on primary cultured rat hepatocytes. The results showed that cultured hepatocytes of rats pretreated with indomethacin in vivo still retained the ability resisting CCl4-induced cytotoxicity, as indicated by lower leakage of enzymes. However, cultured hepatocytes of normal rats treated with indomethacin in vitro had no obvious resistance to CCl4-induced cytotoxicity. The results suggest that indomethacin pretreatment in vivo enables hepatocytes to resist injury, which probably also needs participation of other factors.